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2011 |
Alexander C. Schütz; David Souto Adaptation of catch-up saccades during the initiation of smooth pursuit eye movements Journal Article In: Experimental Brain Research, vol. 209, no. 4, pp. 537–549, 2011. @article{Schuetz2011a,Reduction of retinal speed and alignment of the line of sight are believed to be the respective primary functions of smooth pursuit and saccadic eye movements. As the eye muscles strength can change in the short-term, continuous adjustments of motor signals are required to achieve constant accuracy. While adaptation of saccade amplitude to systematic position errors has been extensively studied, we know less about the adaptive response to position errors during smooth pursuit initiation, when target motion has to be taken into account to program saccades, and when position errors at the saccade endpoint could also be corrected by increasing pursuit velocity. To study short-term adaptation (250 adaptation trials) of tracking eye movements, we introduced a position error during the first catch-up saccade made during the initiation of smooth pursuit-in a ramp-step-ramp paradigm. The target position was either shifted in the direction of the horizontally moving target (forward step), against it (backward step) or orthogonally to it (vertical step). Results indicate adaptation of catch-up saccade amplitude to back and forward steps. With vertical steps, saccades became oblique, by an inflexion of the early or late saccade trajectory. With a similar time course, post-saccadic pursuit velocity was increased in the step direction, adding further evidence that under some conditions pursuit and saccades can act synergistically to reduce position errors. |
Jens Schwarzbach A simple framework (ASF) for behavioral and neuroimaging experiments based on the psychophysics toolbox for MATLAB Journal Article In: Behavior Research Methods, vol. 43, no. 4, pp. 1194–1201, 2011. @article{Schwarzbach2011,The cognitive neurosciences combine behavioral experiments with acquiring physiological data from different modalities, such as electroencephalography, magnetoencephalography, transcranial magnetic stimulation, and functional magnetic resonance imaging, all of which require excellent timing. A simple framework is proposed in which uni- and multimodal experiments can be conducted with minimal adjustments when one switches between modalities. The framework allows the beginner to quickly become productive and the expert to be flexible and not constrained by the tool by building on existing software such as MATLAB and the Psychophysics Toolbox, which already are serving a large community. The framework allows running standard experiments but also supports and facilitates exciting new possibilities for real-time neuroimaging and state-dependent stimulation. |
Christopher R. Sears; Kristin R. Newman; Jennifer D. Ference; Charmaine L. Thomas Attention to emotional images in previously depressed individuals: An eye-tracking study Journal Article In: Cognitive Therapy and Research, vol. 35, no. 6, pp. 517–528, 2011. @article{Sears2011,Depression and dysphoria are associated with attention and memory biases for emotional information (Williams et al. 1997; Yiend in Cogn Emot 24:3-47, 2010), which are postulated to reflect stable vulnerability factors for the development and recurrence of depression (Gotlib and Joormann in Annu Rev Clin Psychol 6:285-312, 2010). The present study looked for evidence of attention and memory biases in individuals with a self-reported history of depression, compared to individuals with dysphoria and individuals with no history of depression. Participants viewed sets of depression-related, anxiety-related, positive, and neutral images while their eye fixations were tracked and recorded. Incidental recognition of the images was assessed 7 days later. Consistent with previous studies (Kellough et al. in Behav Res Therapy 46:1238-1243, 2008; Sears et al. in Cogn Emot 24:1349-1368, 2010), dysphoric individuals spent significantly less time attending to positive images than never depressed individuals, and it was also found that previously depressed individuals exhibited the same attentional bias. Previously depressed individuals also attended to anxiety-related images more than never depressed individuals. A bias in the initial orienting of attention was observed, with previously depressed and dysphoric individuals orienting to depression-images more frequently than never depressed participants. The recognition memory data showed that previously depressed and dysphoric individuals had poorer memory than never depressed individuals, but there was no evidence of a memory bias for either group. Implications for cognitive models of depression and depression vulnerability are discussed. |
Luc P. J. Selen; W. Pieter Medendorp Saccadic updating of object orientation for grasping movements Journal Article In: Vision Research, vol. 51, no. 8, pp. 898–907, 2011. @article{Selen2011,Reach and grasp movements are a fundamental part of our daily interactions with the environment. This spatially-guided behavior is often directed to memorized objects because of intervening eye movements that caused them to disappear from sight. How does the brain store and maintain the spatial representations of objects for future reach and grasp movements? We had subjects (n= 8) make reach and two-digit grasp movements to memorized objects, briefly presented before an intervening saccade. Grasp errors, characterizing the spatial representation of object orientation, depended on current gaze position, with and without intervening saccade. This suggests that the orientation information of the object is coded and updated relative to gaze during intervening saccades, and that the grasp errors arose after the updating stage, during the later transformations involved in grasping. The pattern of reach errors also revealed a gaze-centered updating of object location, consistent with previous literature on updating of single-point targets. Furthermore, grasp and reach errors correlated strongly, but their relationship had a non-unity slope, which may suggest that the gaze-centered spatial updates were made in separate channels. Finally, the errors of the two digits were strongly correlated, supporting the notion that these were not controlled independently to form the grip in these experimental conditions. Taken together, our results suggest that the visuomotor system dynamically represents the short-term memory of location and orientation information for reach-and-grasp movements. |
Matthew C. Shake; Elizabeth A. L. Stine-Morrow Age differences in resolving anaphoric expressions during reading Journal Article In: Aging, Neuropsychology, and Cognition, vol. 18, no. 6, pp. 678–707, 2011. @article{Shake2011,One crucial component of reading comprehension is the ability to bind current information to earlier text, which is often accomplished via anaphoric expressions (e.g., pronouns referring to previous nouns). Processing time for anaphors that violate expectations (e.g., 'The firefighter burned herself while rescuing victims from the building') provide a window into how the semantic representation of the referent is instantiated and retained up to the anaphor. We present data from three eye-tracking experiments examining older and younger adults' reading patterns for passages containing such local expectancy violations. Younger adults quickly registered and resolved the expectancy violation at the point at which it first occurred (as measured by increased gaze duration on the anaphor), regardless of whether sentences were read in isolation or embedded in a discourse context. Older adults, however, immediately noticed the violation only when sentences were embedded in discourse context, suggesting that they relied more on situational grounding to instantiate the referent. For neither young nor old did prior disambiguation within the context (e.g., stating the firefighter was a woman) reduce the effect of the local violation on early processing. For older readers, however, prior disambiguation facilitated anaphor resolution by reducing reprocessing. These results suggest that (a) anaphor resolution unfolds serially, such that prior disambiguating context does not 'inoculate' against local activation of salient (but contextually inappropriate) features, and that (b) older readers use the situational grounding of discourse context to support earlier access to the antecedent, and are more likely to reprocess the context for anaphor resolution. |
Diego E. Shalom; Bruno Dagnino; Mariano Sigman Looking at Breakout: Urgency and predictability direct eye events Journal Article In: Vision Research, vol. 51, no. 11, pp. 1262–1272, 2011. @article{Shalom2011,We investigated the organization of eye-movement classes in a natural and dynamical setup. To mimic the goals and objectives of the natural world in a controlled environment, we studied eye-movements while participants played Breakout, an old Atari game which remains surprisingly entertaining, often addictive, in spite of its graphic and structural simplicity. Our results show that eye-movement dynamics can be explained in terms of simple principles of moments of prediction and urgency of action. We observed a consistent anticipatory behavior (gaze was directed ahead of ball trajectory) except during the moment in which the ball bounced either in the walls, or in the paddle. At these moments, we observed a refractory period during which there are no blinks and saccades. Saccade delay caused the gaze to fall behind the ball. This pattern is consistent with a model by which participants postpone saccades at the bounces while predicting the ball trajectory and subsequently make a catch-up saccade directed to a position which anticipates ball trajectory. During bounces, trajectories were smooth and curved interpolating the V-shape function of the ball with minimal acceleration. These results pave the path to understand the taxonomy of eye-movements on natural configurations in which stimuli and goals switch dynamically in time. |
Swetha Shankar; Dino P. Massoglia; Dantong Zhu; M. Gabriela Costello; Terrence R. Stanford; Emilio Salinas Tracking the temporal evolution of a perceptual judgment using a compelled-response task Journal Article In: Journal of Neuroscience, vol. 31, no. 23, pp. 8406–8421, 2011. @article{Shankar2011,Choice behavior and its neural correlates have been intensely studied with tasks in which a subject makes a perceptual judgment and indicates the result with a motor action. Yet a question crucial for relating behavior to neural activity remains unresolved: what fraction of a subject's reaction time (RT) is devoted to the perceptual evaluation step, as opposed to executing the motor report? Making such timing measurements accurately is complicated because RTs reflect both sensory and motor processing, and because speed and accuracy may be traded. To overcome these problems, we designed the compelled-saccade task, a two-alternative forced-choice task in which the instruction to initiate a saccade precedes the appearance of the relevant sensory information. With this paradigm, it is possible to track perceptual performance as a function of the amount of time during which sensory information is available to influence a subject's choice. The result-the tachometric curve-directly reveals a subject's perceptual processing capacity independently of motor demands. Psychophysical data, together with modeling and computer-simulation results, reveal that task performance depends on three separable components: the timing of the motor responses, the speed of the perceptual evaluation, and additional cognitive factors. Each can vary quickly, from one trial to the next, or can show stable, longer-term changes. This novel dissociation between sensory and motor processes yields a precise metric of how perceptual capacity varies under various experimental conditions and serves to interpret choice-related neuronal activity as perceptual, motor, or both. |
Genevieve Z. Steiner; Robert J. Barry Pupillary responses and event-related potentials as indices of the orienting reflex Journal Article In: Psychophysiology, vol. 48, no. 12, pp. 1648–1655, 2011. @article{Steiner2011,This study examined skin conductance responses, the late positive complex of the event-related potential, and pupillary dilation responses as autonomic and central correlates of the orienting reflex (OR) in the context of indifferent and significant stimuli. In particular, we aimed to clarify the inconsistencies surrounding the pupillary dilation response as an OR index. An auditory dishabituation paradigm was employed, and physiological measures were recorded from 24 participants. Response decrement to a repeated stimulus, response recovery to a change stimulus, and subsequent dishabituation were assessed. Findings confirmed expectations that the skin conductance response and the late positive complex are indices of the OR. The pupillary dilation response, however, demonstrated an unexpected sensitivity to stimulus novelty only, while the prestimulus measure of tonic pupil diameter showed the significance effect that was expected of the phasic measure. Together, these findings argue against the suggestion that the pupillary dilation response is an OR index. The diverse results obtained from this experiment contribute to our understanding of the OR, and provide impetus for further research with a variety of paradigm manipulations. |
Mike Stieff; Mary Hegarty; Ghislain Deslongchamps Identifying representational competence with multi-representational displays Journal Article In: Cognition and Instruction, vol. 29, no. 1, pp. 123–145, 2011. @article{Stieff2011,Increasingly, multi-representational educational technologies are being deployed in science classrooms to support science learning and the development of representational competence. Several studies have indicated that students experience significant challenges working with these multi-representational displays and prefer to use only one representation while problem solving. Here, we examine the use of one such display, a multi-representational molecular mechanics animation, by organic chemistry undergraduates in a problem-solving interview. Using both protocol analysis and eye fixation data, our analysis indicates that students rely mainly on two visual-spatial representations in the display and do not make use of two accompanying mathematical representations. Moreover, we explore how eye fixation data complement verbal protocols by providing information about how students allocate their attention to different locations of a multi-representational display with and without concurrent verbal utterances. Our analysis indicates that verbal protocols and eye movement data are highly correlated, suggesting that eye fixations and verbalizations reflect similar cognitive processes in such studies. |
Viola S. Stormer; Shu-Chen Li; Hauke R. Heekeren; Ulman Lindenberger Feature-based interference from unattended visual field during attentional tracking in younger and older adults Journal Article In: Journal of Vision, vol. 11, no. 2, pp. 1–12, 2011. @article{Stormer2011,The ability to attend to multiple objects that move in the visual field is important for many aspects of daily functioning. The attentional capacity for such dynamic tracking, however, is highly limited and undergoes age-related decline. Several aspects of the tracking process can influence performance. Here, we investigated effects of feature-based interference from distractor objects that appear in unattended regions of the visual field with a hemifield-tracking task. Younger and older participants performed an attentional tracking task in one hemifield while distractor objects were concurrently presented in the unattended hemifield. Feature similarity between objects in the attended and unattended hemifields as well as motion speed and the number of to-be-tracked objects were parametrically manipulated. The results show that increasing feature overlap leads to greater interference from the unattended visual field. This effect of feature-based interference was only present in the slow speed condition, indicating that the interference is mainly modulated by perceptual demands. High-performing older adults showed a similar interference effect as younger adults, whereas low-performing adults showed poor tracking performance overall. |
Michael J. Stroud; Tamaryn Menneer; Kyle R. Cave; Nick Donnelly; Keith Rayner Search for multiple targets of different colours: Misguided eye movements reveal a reduction of colour selectivity Journal Article In: Applied Cognitive Psychology, vol. 25, no. 6, pp. 971–982, 2011. @article{Stroud2011,Searching for two targets simultaneously is often less efficient than conducting two separate searches. Eye movements were tracked to understand the source of this dual-target cost. Findings are discussed in the context of security screening. In both single-target and dual-target search, displays contained one target at most. Stimuli were abstract shapes modeled after guns and other threat items. With these targets and distractors, color information was more helpful in guiding search than shape information. When the two targets had different colors, distractors with colors different from either target were fixated more often in dual-target search than in single-target searches. Thus a dual-target cost arose from a reduction in color selectivity, reflecting limitations in the ability to represent two target features simultaneously and use them to guide search. Because of these limitations, performance in security searches may improve if each image was searched by two screeners, each specializing in a different category of threat item. |
Jessica L. Sullivan; Barbara J. Juhasz; Timothy J. Slattery; Hilary C. Barth Adults' number-line estimation strategies: Evidence from eye movements Journal Article In: Psychonomic Bulletin & Review, vol. 18, no. 3, pp. 557–563, 2011. @article{Sullivan2011,Although the development of number-line estimation ability is well documented, little is known of the processes underlying successful estimators' mappings of numerical information onto spatial representations during these tasks. We tracked adults' eye movements during a number-line estimation task to investigate the processes underlying number-to-space translation, with three main results. First, eye movements were strongly related to the target number's location, and early processing measures directly predicted later estimation performance. Second, fixations and estimates were influenced by the size of the first number presented, indicating that adults calibrate their estimates online. Third, adults' number-line estimates demonstrated patterns of error consistent with the predictions of psychophysical models of proportion estimation, and eye movement data predicted the specific error patterns we observed. These results support proportion-based accounts of number-line estimation and suggest that adults' translation of numerical information into spatial representations is a rapid, online process. |
Aiga Švede; Jörg Hoormann; Stephanie Jainta; Wolfgang Jaschinski Subjective fixation disparity affected by dynamic asymmetry, resting vergence, and nonius bias Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 7, pp. 4356–4361, 2011. @article{Svede2011,PURPOSE. This study was undertaken to investigate how sub- jectively measured fixation disparity can be explained by (1) the convergent–divergent asymmetry of vergence dynamics (called dynamic asymmetry) for a disparity vergence step stimulus of 1° (60 arc min), (2) the dark vergence, and (3) the nonius bias. METHODS. Fixation disparity, dark vergence, and nonius bias were measured subjectively using nonius lines. Dynamic vergence step responses (both convergent and divergent) were measured objectively. RESULTS. In 20 subjects (mean age, 24.5 ⫾ 4.3 years, visual acuity, ≥1.0; all emmetropic except for one with myopia, wearing contact lenses), multiple regression analyses showed that 39% of the variance in subjective fixation disparity was due to the characteristic factors of physiological vergence: dynamic asymmetry (calculated from convergent and divergent veloci- ties), and dark vergence. An additional 23% of variance was due to the subjective nonius bias (i.e., the physical nonius offset required for perceived alignment of binocularly [nondichopti- cally] presented nonius lines). Together, these factors ex- plained 62% of the interindividual differences in subjectively measured fixation disparity, demonstrating the influence of oculomotor and perceptual factors. CONCLUSIONS. Clinically relevant subjective fixation disparity originates from distinct physiological sources. Dynamic asym- metry in vergence dynamics, resting vergence, and nonius bias were found to affect fixation disparity directly, not only via changes in vergence dynamics. |
Hua Shu; Wei Zhou; Ming Yan; Reinhold Kliegl Font size modulates saccade-target selection in chinese reading Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 2, pp. 482–490, 2011. @article{Shu2011,In alphabetic writing systems, saccade amplitude (a close correlate of reading speed) is independent of font size, presumably because an increase in the angular size of letters is compensated for by a decrease of visual acuity with eccentricity. We propose that this invariance may (also) be due to the presence of spaces between words, guiding the eyes across a large range of font sizes. Here, we test whether saccade amplitude is also invariant against manipulations of font size during reading Chinese, a character-based writing system without spaces as explicit word boundaries for saccade-target selection. In contrast to word-spaced alphabetic writing systems, saccade amplitude decreased significantly with increased font size, leading to an increase in the number of fixations at the beginning of words and in the number of refixations. These results are consistent with a model which assumes that word beginning (rather than word center) is the default saccade target if the length of the parafoveal word is not available. |
Alisha Siebold; Wieske Zoest; Mieke Donk Oculomotor evidence for top-down control following the initial saccade Journal Article In: PLoS ONE, vol. 6, no. 9, pp. e23552, 2011. @article{Siebold2011,The goal of the current study was to investigate how salience-driven and goal-driven processes unfold during visual search over multiple eye movements. Eye movements were recorded while observers searched for a target, which was located on (Experiment 1) or defined as (Experiment 2) a specific orientation singleton. This singleton could either be the most, medium, or least salient element in the display. Results were analyzed as a function of response time separately for initial and second eye movements. Irrespective of the search task, initial saccades elicited shortly after the onset of the search display were primarily salience-driven whereas initial saccades elicited after approximately 250 ms were completely unaffected by salience. Initial saccades were increasingly guided in line with task requirements with increasing response times. Second saccades were completely unaffected by salience and were consistently goal-driven, irrespective of response time. These results suggest that stimulus-salience affects the visual system only briefly after a visual image enters the brain and has no effect thereafter. |
Sara Ann Simpson; Mathias Abegg; Jason J. S. Barton Rapid adaptation of visual search in simulated hemianopia Journal Article In: Cerebral Cortex, vol. 21, no. 7, pp. 1593–1601, 2011. @article{Simpson2011,Patients with homonymous hemianopia have altered visual search patterns, but it is unclear how rapidly this develops and whether it reflects a strategic adaptation to altered perception or plastic changes to tissue damage. To study the temporal dynamics of adaptation alone, we used a gaze-contingent display to simulate left or right hemianopia in 10 healthy individuals as they performed 25 visual search trials. Visual search was slower and less accurate in hemianopic than in full-field viewing. With full-field viewing, there were improvements in search speed, fixation density, and number of fixations over the first 9 trials, then stable performance. With hemianopic viewing, there was a rapid shift of fixation into the blind field over the first 5-7 trials, followed by continuing gradual improvements in completion time, number of fixations, and fixation density over all 25 trials. We conclude that in the first minutes after onset of hemianopia, there is a biphasic pattern of adaptation to altered perception: an early rapid qualitative change that shifts visual search into the blind side, followed by more gradual gains in the efficiency of using this new strategy, a pattern that has parallels in other studies of motor learning. |
Chris R. Sims; Robert A. Jacobs; David C. Knill Adaptive allocation of vision under competing task temands Journal Article In: Journal of Neuroscience, vol. 31, no. 3, pp. 928–943, 2011. @article{Sims2011,Human behavior in natural tasks consists of an intricately coordinated dance of cognitive, perceptual, and motor activities. Although much research has progressed in understanding the nature of cognitive, perceptual, or motor processing in isolation or in highly constrained settings, few studies have sought to examine how these systems are coordinated in the context of executing complex behavior. Previous research has suggested that, in the course of visually guided reaching movements, the eye and hand are yoked, or linked in a nonadaptive manner. In this work, we report an experiment that manipulated the demands that a task placed on the motor and visual systems, and then examined in detail the resulting changes in visuomotor coordination. We develop an ideal actor model that predicts the optimal coordination of vision and motor control in our task. On the basis of the predictions of our model, we demonstrate that human performance in our experiment reflects an adaptive response to the varying costs imposed by our experimental manipulations. Our results stand in contrast to previous theories that have assumed a fixed control mechanism for coordinating vision and motor control in reaching behavior. |
Petra Sinn; Ralf Engbert Saccadic facilitation by modulation of microsaccades in natural backgrounds Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 4, pp. 1029–1033, 2011. @article{Sinn2011,Saccades move objects of interest into the center of the visual field for high-acuity visual analysis. White, Stritzke, and Gegenfurtner (Current Biology, 18, 124-128, 2008) have shown that saccadic latencies in the context of a structured background are much shorter than those with an unstructured background at equal levels of visibility. This effect has been explained by possible preactivation of the saccadic circuitry whenever a structured background acts as a mask for potential saccade targets. Here, we show that background textures modulate rates of microsaccades during visual fixation. First, after a display change, structured backgrounds induce a stronger decrease of microsaccade rates than do uniform backgrounds. Second, we demonstrate that the occurrence of a microsaccade in a critical time window can delay a subsequent saccadic response. Taken together, our findings suggest that microsaccades contribute to the saccadic facilitation effect, due to a modulation of microsaccade rates by properties of the background. |
Anna Siyanova-Chanturia; Kathy Conklin; Norbert Schmitt Adding more fuel to the fire: An eye-tracking study of idiom processing by native and non-native speakers Journal Article In: Second Language Research, vol. 27, no. 2, pp. 251–272, 2011. @article{SiyanovaChanturia2011,Using eye-tracking, we investigate on-line processing of idioms in a biasing story context by native and non-native speakers of English. The stimuli are idioms used figuratively ("at the end of the day"--"eventually"), literally ("at the end of the day"--"in the evening"), and novel phrases ("at the end of the war"). Native speaker results indicate a processing advantage for idioms over novel phrases, as evidenced by fewer and shorter fixations. Further, no processing advantage is found for figurative idiom uses over literal ones in a full idiom analysis or in a recognition point analysis. Contrary to native speaker results, non-native findings suggest that L2 speakers process idioms at a similar speed to novel phrases. Further, figurative uses are processed more slowly than literal ones. Importantly, the recognition point analysis allows us to establish where non-natives slow down when processing the figurative meaning. |
Anna Siyanova-Chanturia; Kathy Conklin; Walter J. B. Heuven Seeing a phrase "time and again" matters: The role of phrasal frequency in the processing of multiword sequences Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 37, no. 3, pp. 776–784, 2011. @article{SiyanovaChanturia2011a,Are speakers sensitive to the frequency with which phrases occur in language? The authors report an eye-tracking study that investigates this by examining the processing of multiword sequences that differ in phrasal frequency by native and proficient nonnative English speakers. Participants read sentences containing 3-word binomial phrases (bride and groom) and their reversed forms (groom and bride), which are identical in syntax and meaning but that differ in phrasal frequency. Mixed-effects modeling revealed that native speakers and nonnative speakers, across a range of proficiencies, are sensitive to the frequency with which phrases occur in English. Results also indicate that native speakers and higher proficiency nonnatives are sensitive to whether a phrase occurs in a particular configuration (binomial vs. reversed) in English, highlighting the contribution of entrenchment of a particular phrase in memory. |
Timothy J. Slattery; Bernhard Angele; Keith Rayner Eye movements and display change detection during reading Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 37, no. 6, pp. 1924–1938, 2011. @article{Slattery2011,In the boundary change paradigm (Rayner, 1975), when a reader's eyes cross an invisible boundary location, a preview word is replaced by a target word. Readers are generally unaware of such changes due to saccadic suppression. However, some readers detect changes on a few trials and a small percentage of them detect many changes. Two experiments are reported in which we combined eye movement data with signal detection analyses to investigate display change detection. On each trial, readers had to indicate if they saw a display change in addition to reading for meaning. On half the trials the display change occurred during the saccade (immediate condition); on the other half, it was slowed by 15-25 ms (delay condition) to increase the likelihood that a change would be detected. Sentences were presented in an alternating case fashion allowing us to investigate the influence of both letter identity and case. In the immediate condition, change detection was higher when letters changed than when case changed corroborating findings that word processing utilizes abstract (case independent) letter identities. However, in the delay condition (where d' was much higher than the immediate condition), detection was equal for letter and case changes. The results of both experiments indicate that sensitivity to display changes was related to how close the eyes were to the invalid preview on the fixation prior to the display change, as well as the timing of the completion of this change relative to the start of the post-change fixation. |
Timothy J. Slattery; Elizabeth R. Schotter; Raymond W. Berry; Keith Rayner Parafoveal and foveal processing of abbreviations during eye fixations in reading: Making a case for case Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 37, no. 4, pp. 1022–1031, 2011. @article{Slattery2011a,The processing of abbreviations in reading was examined with an eye movement experiment. Abbreviations were of 2 distinct types: acronyms (abbreviations that can be read with the normal grapheme-phoneme correspondence [GPC] rules, such as NASA) and initialisms (abbreviations in which the GPCs are letter names, such as NCAA). Parafoveal and foveal processing of these abbreviations was assessed with the use of the boundary change paradigm (K. Rayner, 1975). Using this paradigm, previews of the abbreviations were either identical to the abbreviation (NASA or NCAA), orthographically legal (NUSO or NOBA), or illegal (NRSB or NRBA). The abbreviations were presented as capital letter strings within normal, predominantly lowercase sentences and also sentences in all capital letters such that the abbreviations would not be visually distinct. The results indicate that acronyms and initialisms undergo different processing during reading and that readers can modulate their processing based on low-level visual cues (distinct capitalization) in parafoveal vision. In particular, readers may be biased to process capitalized letter strings as initialisms in parafoveal vision when the rest of the sentence is normal, lowercase letters. |
Elke Smeets; Anita Jansen; Anne Roefs Bias for the (un)attractive self: On the role of attention in causing body (dis)satisfaction Journal Article In: Health Psychology, vol. 30, no. 3, pp. 360–367, 2011. @article{Smeets2011,Objective: Body dissatisfaction plays a key role in the maintenance of eating disorders, and selective attention might be crucial for the origin of body dissatisfaction. A. Jansen, C. Nederkoorn, and S. Mulkens (2005) showed that eating disorder patients attend relatively more to their own unattractive body parts, whereas healthy controls attend relatively more to their own attractive body parts. In 2 studies, we investigated whether this bias in selective attention is causal to body dissatisfaction and whether an experimentally induced bias for attractive body parts might lead to increased body satisfaction in women who are highly dissatisfied with their bodies. Design: We used a between-subjects design in which participants were trained to attend to either their self-defined unattractive body parts or their self-defined attractive body parts by use of an eye tracker. Main Outcome Measures: State body and weight satisfaction. Results: Inducing a temporary attentional bias for self-defined unattractive body parts led to a significant decrease in body satisfaction and teaching body-dissatisfied women to attend to their own attractive body parts led to a significant increase in body satisfaction. Conclusion: Selective attention for unattractive body parts can play a role in the development of body dissatisfaction, and changing the way one looks may be a new way for improving body dissatisfaction in women. |
Nicholas D. Smith; David P. Crabb; David F. Garway-Heath An exploratory study of visual search performance in glaucoma Journal Article In: Ophthalmic and Physiological Optics, vol. 31, no. 3, pp. 225–232, 2011. @article{Smith2011,PURPOSE: Visual search plays an integral role in many daily activities. This study aimed to determine whether patients with glaucoma are slower than visually healthy age-matched individuals when searching for items in computer displayed images. METHODS: Forty participants were recruited for the study: 20 patients with a clinical diagnosis of glaucoma and 20 age-similar visually healthy control subjects. All participants had visual acuity of 6/12 or better. Participants were presented with 20 images with Landolt C symbols and 15 photographic images of everyday scenes on a computer. The time taken by each participant to locate a specified item in each image was recorded. Average search times were calculated across participants and compared between groups. RESULTS: All the patients had visual field defects in both eyes. On average, the patients also differed from control subjects by binocular contrast sensitivity measurements (p = 0.01) and visual acuity (p = 0.003). The patients (mean age = 67 years, S.D.: 10 years) and controls (mean age: 67 years, S.D.: 11 years) were age similar (p = 0.40). The median search time for patients finding target items in photographs of everyday scenes was 15.2 s (interquartile range 9.4-20.6 s) and this was significantly slower than the median time (10.0 s; interquartile range 7.2-10.3 s) taken by the controls (p = 0.007). There was no statistical evidence for a difference in median search times between groups in the Landolt C search task (p = 0.24). CONCLUSION: Some individuals with glaucomatous visual field defects in both eyes find it especially difficult to locate objects in photographs of everyday scenes when compared to visually healthy individuals of a similar age. |
Tim J. Smith; John M. Henderson Does oculomotor inhibition of return influence fixation probability during scene search? Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 8, pp. 2384–2398, 2011. @article{Smith2011a,Oculomotor inhibition of return (IOR) is believed to facilitate scene scanning by decreasing the probability that gaze will return to a previously fixated location. This "foraging" hypothesis was tested during scene search and in response to sudden-onset probes at the immediately previous (one-back) fixation location. The latencies of saccades landing within 1textordmasculine of the previous fixation location were elevated, consistent with oculomotor IOR. However, there was no decrease in the likelihood that the previous location would be fixated relative to distance-matched controls or an a priori baseline. Saccades exhibit an overall forward bias, but this is due to a general bias to move in the same direction and for the same distance as the last saccade (saccadic momentum) rather than to a spatially specific tendency to avoid previously fixated locations. We find no evidence that oculomotor IOR has a significant impact on return probability during scene search. |
Tim J. Smith; John M. Henderson Looking back at Waldo: Oculomotor inhibition of return does not prevent return fixations Journal Article In: Journal of Vision, vol. 11, no. 1, pp. 1–11, 2011. @article{Smith2011b,Inhibition of Return (IOR) is a difficulty in processing stimuli presented at recently attended locations. IOR is widely believed to facilitate foraging of a visual scene by decreasing the probability that gaze will return to previously fixated locations. However, there is a lack of clear evidence in support of the foraging facilitator hypothesis during scene search. The original R. M. Klein andW. J. MacInnes' (1999) Where'sWaldo study reported a forward bias in the distribution of fixations that was taken as evidence for the foraging facilitator hypothesis. The present study was designed to replicate R. M. Klein and W. J. R. M. Klein andW. J. MacInnes' (1999) Where'sWaldo study reported a forward bias in the distribution of fixations that was taken as evidence for the foraging facilitator hypothesis. The present study was designed to replicate R. M. Klein and W. J. MacInnes' (1999) but include detailed analysis of fixation distributions in order to test the precise predictions of the foraging facilitator hypothesis. The results indicate that latencies of saccades returning to 1-back (and possibly 2-back) locations MacInnes' (1999) but include detailed analysis of fixation distributions in order to test the precise predictions of the foraging facilitator hypothesis. The results indicate that latencies of saccades returning to 1-back (and possibly 2-back) locations during visual search are elevated. However, there is no evidence that the probability of returning to these locations is significantly less than control locations. Eye movement behavior during search of visual scenes does not support the view that IOR facilitates foraging. |
Raju P. Sapkota; Shahina Pardhan; Ian Linde The impact of extrafoveal information on visual short-term memory for object position Journal Article In: Journal of Cognitive Psychology, vol. 23, no. 5, pp. 574–585, 2011. @article{Sapkota2011,The role of extrafoveal information in visual short-term memory has been investigated relatively little, and, in most existing studies, using verbalisable stimuli susceptible to the recruitment of long-term memory (LTM). In addition, little is known about the impact of extrafoveal information available pre-and posttarget foveation, as it is typical to provide extrafoveal information prior to the foveation of memory targets. In this study, two object-position recognition experiments were conducted (each with two conditions) to establish the impact of extrafoveal information provided before and after the foveation of memory targets. Stimuli comprised 1/f noise discs that minimised the recruitment of LTM by eliminating verbal and semantic cues. Overall, a greater hit rate was found where extrafoveal information was available; however, performance analyses in which extrafoveal information was considered relative to the temporal lag at which target stimuli were foveated reveals both costs and benefits. A beneficial effect arose only where extrafoveal information was provided after the target had been foveated, but not prior to target foveation. Findings are discussed in terms of recency and extrafoveal perception effects, incorporating a postfoveation object-file refresh mechanism. |
Paige E. Scalf; Chandramalika Basak; Diane M. Beck Attention does more than modulate suppressive interactions: Attending to multiple items Journal Article In: Experimental Brain Research, vol. 212, no. 2, pp. 293–304, 2011. @article{Scalf2011,Directing attention to a visual item enhances its representations, making it more likely to guide behavior (Corbetta et al. 1991). Attention is thought to produce this enhancement by biasing suppressive interactions among multiple items in visual cortex in favor of the attended item (e.g., Desimone and Duncan 1995; Reynolds and Heeger 2009). We ask whether target enhancement and modulation of suppressive interactions are in fact inextricably linked or whether they can be decoupled. In particular, we ask whether simultaneously directing attention to multiple items may be one means of dissociating the influence of attention-related enhancement from the effects of inter-item suppression. When multiple items are attended, suppressive interactions in visual cortex limit the effectiveness with which attention may act on their representations, presumably because "biasing" the interactions in favor of a single item is no longer possible (Scalf and Beck 2010). In this experiment, we directly investigate whether applying attention to multiple competing stimulus items has any influence on either their evoked signal or their suppressive interactions. Both BOLD signal evoked by the items in V4 and behavioral responses to those items were significantly compromised by simultaneous presentation relative to simultaneous presentation, indicating that when the items appeared at the same time, they interacted in a mutually suppressive manner that compromised their ability to guide behavior. Attention significantly enhanced signal in V4. The attentional status of the items, however, had no influence on the suppressive effects of simultaneous presentation. To our knowledge, these data are the first to explicitly decouple the effects of top-down attention from those of inter-item suppression. |
Patrick Schleifer; Karin Landerl Subitizing and counting in typical and atypical development Journal Article In: Developmental Science, vol. 14, no. 2, pp. 280–291, 2011. @article{Schleifer2011,Enumeration performance in standard dot counting paradigms was investigated for different age groups with typical and atypically poor development of arithmetic skills. Experiment 1 showed a high correspondence between response times and saccadic frequencies for four age groups with typical development. Age differences were more marked for the counting than the subitizing range. In Experiment 2 we found a discontinuity between subitizing and counting for dyscalculic children; however, their subitizing slopes were steeper than those of typically developing control groups, indicating a dysfunctional subitizing mechanism. Across both experiments a number of factors could be identified that affect enumeration in the subitizing and the counting range differentially. These differential patterns further support the assumption of two qualitatively different enumeration processes. |
Joseph Schmidt; Gregory J. Zelinsky Visual search guidance is best after a short delay Journal Article In: Vision Research, vol. 51, no. 6, pp. 535–545, 2011. @article{Schmidt2011,Search displays are typically presented immediately after a target cue, but in the real-world, delays often exist between target designation and search. Experiments 1 and 2 asked how search guidance changes with delay. Targets were cued using a picture or text label, each for 3000ms, followed by a delay up to 9000ms before the search display. Search stimuli were realistic objects, and guidance was quantified using multiple eye movement measures. Text-based cues showed a non-significant trend towards greater guidance following any delay relative to a no-delay condition. However, guidance from a pictorial cue increased sharply 300-600ms after preview offset. Experiment 3 replicated this guidance enhancement using shorter preview durations while equating the time from cue onset to search onset, demonstrating that the guidance benefit is linked to preview offset rather than a more complete encoding of the target. Experiment 4 showed that enhanced guidance persists even with a mask flashed at preview offset, suggesting an explanation other than visual priming. We interpret our findings as evidence for the rapid consolidation of target information into a guiding representation, which attains its maximum effectiveness shortly after preview offset. |
Grayden J. F. Solman; J. A. Cheyne; Daniel Smilek; J. Allan Cheyne; Daniel Smilek Memory load affects visual search processes without influencing search efficiency Journal Article In: Vision Research, vol. 51, no. 10, pp. 1185–1191, 2011. @article{Solman2011,Participants' eye-movements were monitored while they searched for a target among a varying number of distractors either with or without a concurrent memory load. Consistent with previous findings, adding a memory load slowed response times without affecting search slopes; a finding normally taken to imply that memory load affects pre- and/or post-search processes but not the search process itself. However, when overall response times were decomposed using eye-movement data into pre-search (e.g., initial encoding), search, and post-search (e.g., response selection) phases, analysis revealed that adding a memory load affected all phases, including the search phase. In addition, we report that fixations selected under load were more likely to be distant from search items, and more likely to be close to previously inspected locations. Thus, memory load affects the search process without affecting search slopes. These results challenge standard interpretations of search slopes and main effects in visual search. |
Joo-Hyun Song; Robert D. Rafal; Robert M. McPeek Deficits in reach target selection during inactivation of the midbrain superior colliculus Journal Article In: Proceedings of the National Academy of Sciences, vol. 108, no. 51, pp. E1433–E1440, 2011. @article{Song2011,Purposive action requires the selection of a single movement goal from multiple possibilities. Neural structures involved in movement planning and execution often exhibit activity related to target selection. A key question is whether this activity is specific to the type of movement produced by the structure, perhaps consisting of a competition among effector-specific movement plans, or whether it constitutes a more abstract, effector-independent selection signal. Here, we show that temporary focal inactivation of the primate superior colliculus (SC), an area involved in eye-movement target selection and execution, causes striking target selection deficits for reaching movements, which cannot be readily explained as a simple impairment in visual perception or motor execution. This indicates that target selection activity in the SC does not simply represent a competition among eye-movement goals and, instead, suggests that the SC contributes to a more general purpose priority map that influences target selection for other actions, such as reaches. |
Miriam Spering; Marc Pomplun; Marisa Carrasco Tracking without perceiving: A dissociation between eye movements and motion perception Journal Article In: Psychological Science, vol. 22, no. 2, pp. 216–225, 2011. @article{Spering2011,Can people react to objects in their visual field that they do not consciously perceive? We investigated how visual perception and motor action respond to moving objects whose visibility is reduced, and we found a dissociation between motion processing for perception and for action. We compared motion perception and eye movements evoked by two orthogonally drifting gratings, each presented separately to a different eye. The strength of each monocular grating was manipulated by inducing adaptation to one grating prior to the presentation of both gratings. Reflexive eye movements tracked the vector average of both gratings (pattern motion) even though perceptual responses followed one motion direction exclusively (component motion). Observers almost never perceived pattern motion. This dissociation implies the existence of visual-motion signals that guide eye movements in the absence of a corresponding conscious percept. |
Miriam Spering; Alexander C. Schütz; Doris I. Braun; Karl R. Gegenfurtner Keep your eyes on the ball: Smooth pursuit eye movements enhance prediction of visual motion Journal Article In: Journal of Neurophysiology, vol. 105, no. 4, pp. 1756–1767, 2011. @article{Spering2011a,Success of motor behavior often depends on the ability to predict the path of moving objects. Here we asked whether tracking a visual object with smooth pursuit eye movements helps to predict its motion direction. We developed a paradigm, "eye soccer," in which observers had to either track or fixate a visual target (ball) and judge whether it would have hit or missed a stationary vertical line segment (goal). Ball and goal were presented briefly for 100-500 ms and disappeared from the screen together before the perceptual judgment was prompted. In pursuit conditions, the ball moved towards the goal; in fixation conditions, the goal moved towards the stationary ball, resulting in similar retinal stimulation during pursuit and fixation. We also tested the condition in which the goal was fixated and the ball moved. Motion direction prediction was significantly better in pursuit than in fixation trials, regardless of whether ball or goal served as fixation target. In both fixation and pursuit trials, prediction performance was better when eye movements were accurate. Performance also increased with shorter ball-goal distance and longer presentation duration. A longer trajectory did not affect performance. During pursuit, an efference copy signal might provide additional motion information, leading to the advantage in motion prediction. |
Andreas Sprenger; Peter Trillenberg; Jonas Pohlmann; Kirsten Herold; Rebekka Lencer; Christoph Helmchen The role of prediction and anticipation on age-related effects on smooth pursuit eye movements Journal Article In: Annals of the New York Academy of Sciences, vol. 1233, pp. 168–176, 2011. @article{Sprenger2011,Externally guided sensory-motor processes deteriorate with increasing age. Internally guided, for example, predictive, behavior usually helps to overcome sensory-motor delays. We studied whether predictive components of visuomotor transformation decline with age. We investigated smooth pursuit eye movements (SPEM) of 45 healthy subjects with paradigms of different degrees of predictability with respect to target motion onset, type (smoothed triangular, ramp stimulation), and direction by blanking the target at various intervals of the ramp stimulation. Using repetitive trials of SPEM stimulation, we could dissociate anticipatory and predictive components of extraretinal smooth pursuit behavior. The main results suggest that basic motor parameters decline with increasing age, whereas both anticipation and prediction of target motion did not change with age. We suggest that the elderly maintain their capability of using prediction in the immediate control of motor behavior, which might be a way to compensate for age-related delays in sensory-motor transformation, even in the absence of sensory signals. |
Adrian Staub The effect of lexical predictability on distributions of eye fixation durations Journal Article In: Psychonomic Bulletin & Review, vol. 18, no. 2, pp. 371–376, 2011. @article{Staub2011,A word's predictability in context has a well-established effect on fixation durations in reading. To investigate how this effect is manifested in distributional terms, an experiment was carried out in which subjects read each of 50 target words twice, once in a high-predictability context and once in a low-predictability context. The ex-Gaussian distribution was fit to each subject's first-fixation durations and single-fixation durations. For both measures, the $mu$ parameter increased when a word was unpredictable, while the $tau$ parameter was not significantly affected, indicating that a predictability manipulation shifts the distribution of fixation durations but does not affect the degree of skew. Vincentile plots showed that the mean ex-Gaussian parameters described the typical distribution shapes extremely well. These results suggest that the predictability and frequency effects are functionally distinct, since a frequency manipulation has been shown to influence both $mu$ and $tau$. The results may also be seen as consistent with the finding from single-word recognition paradigms that semantic priming affects only $mu$. |
Adrian Staub Word recognition and syntactic attachment in reading: Evidence for a staged architecture Journal Article In: Journal of Experimental Psychology: General, vol. 140, no. 3, pp. 407–433, 2011. @article{Staub2011a,In 3 experiments, the author examined how readers' eye movements are influenced by joint manipulations of a word's frequency and the syntactic fit of the word in its context. In the critical conditions of the first 2 experiments, a high- or low-frequency verb was used to disambiguate a garden-path sentence, while in the last experiment, a high- or low-frequency verb constituted a phrase structure violation. The frequency manipulation always influenced the early eye movement measures of first-fixation duration and gaze duration. The context manipulation had a delayed effect in Experiment 1, influencing only the probability of a regressive eye movement from later in the sentence. However, the context manipulation influenced the same early eye movement measures as the frequency effect in Experiments 2 and 3, though there was no statistical interaction between the effects of these variables. The context manipulation also influenced the probability of a regressive eye movement from the verb, though the frequency manipulation did not. These results are shown to confirm predictions emerging from the serial, staged architecture for lexical and integrative processing of the E-Z Reader 10 model of eye movement control in reading (Reichle, Warren, & McConnell, 2009). It is argued, more generally, that the results provide an important constraint on how the relationship between visual word recognition and syntactic attachment is treated in processing models. |
Maria Staudte; Matthew W. Crocker Investigating joint attention mechanisms through spoken human-robot interaction Journal Article In: Cognition, vol. 120, no. 2, pp. 268–291, 2011. @article{Staudte2011,Referential gaze during situated language production and comprehension is tightly coupled with the unfolding speech stream (Griffin, 2001; Meyer, Sleiderink, & Levelt, 1998; Tanenhaus, Spivey-Knowlton, Eberhard, & Sedivy, 1995). In a shared environment, utterance comprehension may further be facilitated when the listener can exploit the speaker's focus of (visual) attention to anticipate, ground, and disambiguate spoken references. To investigate the dynamics of such gaze-following and its influence on utterance comprehension in a controlled manner, we use a human-robot interaction setting. Specifically, we hypothesize that referential gaze is interpreted as a cue to the speaker's referential intentions which facilitates or disrupts reference resolution. Moreover, the use of a dynamic and yet extremely controlled gaze cue enables us to shed light on the simultaneous and incremental integration of the unfolding speech and gaze movement.We report evidence from two eye-tracking experiments in which participants saw videos of a robot looking at and describing objects in a scene. The results reveal a quantified benefit-disruption spectrum of gaze on utterance comprehension and, further, show that gaze is used, even during the initial movement phase, to restrict the spatial domain of potential referents. These findings more broadly suggest that people treat artificial agents similar to human agents and, thus, validate such a setting for further explorations of joint attention mechanisms. |
Sarim Mohammad; Irene Gottlob; Anil Kumar; Mervyn G. Thomas; Christopher Degg; Viral Sheth; Frank A. Proudlock The functional significance of foveal abnormalities in albinism measured using spectral-domain optical coherence tomography Journal Article In: Ophthalmology, vol. 118, no. 8, pp. 1645–1652, 2011. @article{Mohammad2011,Purpose: The relationship between foveal abnormalities in albinism and best-corrected visual acuity (BCVA) is unclear. High-resolution spectral-domain optical coherence tomography (SD OCT) was used to quantify foveal retinal layer thicknesses and to assess the functional significance of foveal morphologic features in patients with albinism. Design: Cross-sectional study. Participants: Forty-seven patients with albinism and 20 healthy control volunteers were recruited to the study. Methods: Using high-resolution SD OCT, 7×7×2-mm volumetric scans of the fovea were acquired (3-$mu$m axial resolution). The B scan nearest the center of the fovea was identified using signs of foveal development. The thickness of each retinal layer at the fovea and foveal pit depth were quantified manually using ImageJ software and were compared with BCVA. Main Outcome Measures: Total retinal thickness, foveal pit depth, photoreceptor layer thickness, and processing layer thickness in relation to BCVA. Results: Total photoreceptor layer thickness at the fovea was correlated highly to BCVA (P = 0.0008; r = 0.501). Of the photoreceptor layers, the outer segment length was correlated most strongly to BCVA (P<0.0001; r = 0.641). In contrast, there was no significant correlation between either total retinal thickness or pit depth and BCVA (P>0.05). This was because of an inverse correlation between total photoreceptor layer thickness and total processing layer thickness (P<0.0001; r = 0.696). Conclusions: Neither the total retinal thickness nor the pit depth are reliable indicators of visual deficit, because patients with similar overall retinal thickness had widely varying foveal morphologic features. In albinism, the size of the photoreceptor outer segment was found to be the strongest predictor of BCVA. These results suggest that detailed SD OCT images of photoreceptor anatomic features provide a useful tool in assessing the visual potential in patients with albinism. |
Jeff Moher; Jared Abrams; Howard E. Egeth; Steven Yantis; Veit Stuphorn Trial-by-trial adjustments of top-down set modulate oculomotor capture Journal Article In: Psychonomic Bulletin & Review, vol. 18, no. 5, pp. 897–903, 2011. @article{Moher2011,The role of top-down control in visual search has been a subject of much debate. Recent research has focused on whether attentional and oculomotor capture by irrelevant salient distractors can be modulated through top-down control, and if so, whether top-down control can be rapidly initiated based on current task goals. In the present study, participants searched for a unique shape in an array containing otherwise homogeneous shapes. A cue prior to each trial indicated the probability that an irrelevant color singleton distractor would appear on that trial. Initial saccades were less likely to land on the target and participants took longer to initiate a saccade to the target when a color distractor was present than when it was absent; this cost was greatly reduced on trials in which the probability that a distractor would appear was high, as compared to when the probability was low. These results suggest that top-down control can modulate oculomotor capture in visual search, even in a singleton search task in which distractors are known to readily capture both attention and the eyes. Furthermore, the results show that top-down distractor suppression mechanisms can be initiated quickly in anticipation of irrelevant salient distractors and can be adjusted on a trial-by-trial basis. |
Pierre Morel; Sophie Deneve; Pierre Baraduc Optimal and suboptimal use of postsaccadic vision in sequences of saccades Journal Article In: Journal of Neuroscience, vol. 31, no. 27, pp. 10039–10049, 2011. @article{Morel2011,Saccades are imprecise, due to sensory and motor noise. To avoid an accumulation of errors during sequences of saccades, a prediction derived from the efference copy can be combined with the reafferent visual feedback to adjust the following eye movement. By varying the information quantity of the visual feedback, we investigated how the reliability of the visual information affects the postsaccadic update in humans. Two elements of the visual scene were manipulated, the saccade target or the background, presented either together or in isolation. We determined the weight of the postsaccadic visual information by measuring the effect of intrasaccadic visual shifts on the following saccade. We confirmed that the weight of visual information evolves with information quantity as predicted for a statistically optimal system. In particular, we found that the visual background alone can guide the postsaccadic update, and that information from target and background are optimally combined. Moreover, these visual weights are adjusted dynamically and on a trial-to-trial basis to the level of visual noise determined by target eccentricity and reaction time. In contrast, we uncovered a dissociation between the visual signals used to update the next planned saccade (main saccade) and those used to generate an involuntary corrective saccade. The latter was exclusively based on visual information about the target, and discarded all information about the background: a suboptimal use of visual evidence. |
Sofie Moresi; Jos J. Adam; Jons Rijcken; Harm Kuipers; Marianne Severens; Pascal W. M. Van Gerven Response preparation with adjacent versus overlapped hands: A pupillometric study Journal Article In: International Journal of Psychophysiology, vol. 79, no. 2, pp. 280–286, 2011. @article{Moresi2011,Preparatory cues facilitate performance in speeded choice tasks. It is debated, however, whether the lateralized neuro-anatomical organization of the human motor system contributes to this facilitation. To investigate this issue, we examined response preparation in a finger-cuing task using two conditions. In the hands adjacent condition, the hands were placed adjacently to each other with index and middle fingers placed on four linearly arrayed response keys. In the overlapped hand placement condition, the fingers of different hands alternated, thus dissociating hand and spatial position factors. Preparatory cues specified a subset of two fingers. Left-right cues specified the two leftmost or two rightmost fingers. Inner-outer cues specified the two inner or outer fingers. Alternate cues specified the first and third, or the second and fourth finger in the response set. In addition to reaction time and response errors, we measured the pupillary response to assess the cognitive processing load associated with response preparation. Results showed stronger pupil dilations (and also longer RTs and more errors) for the overlapped than for the adjacent hand placement condition, reflecting an overall increase in cognitive processing load. Furthermore, the negative impact of overlapping the hands on pupil dilation interacted with cue type, indicating that left-right cues (associated with two fingers on one hand) suffered most from overlapping the hands. With the hands overlapped, alternate cues (now associated with two fingers on the same hand) produced the shortest RTs. These findings demonstrate the importance of motoric factors in response preparation. |
Isamu Motoyoshi Attentional modulation of temporal contrast sensitivity in human vision Journal Article In: PLoS ONE, vol. 6, no. 4, pp. e19303, 2011. @article{Motoyoshi2011,Recent psychophysical studies have shown that attention can alter contrast sensitivities for temporally broadband stimuli such as flashed gratings. The present study examined the effect of attention on the contrast sensitivity for temporally narrowband stimuli with various temporal frequencies. Observers were asked to detect a drifting grating of 0-40 Hz presented gradually in the peripheral visual field with or without a concurrent letter identification task in the fovea. We found that removal of attention by the concurrent task reduced the contrast sensitivity for gratings with low temporal frequencies much more profoundly than for gratings with high temporal frequencies and for flashed gratings. The analysis revealed that the temporal contrast sensitivity function had a more band-pass shape with poor attention. Additional experiments showed that this was also true when the target was presented in various levels of luminance noise. These results suggest that regardless of the presence of external noise, attention extensively modulates visual sensitivity for sustained retinal inputs. |
Christina Moutsiana; David T. Field; John P. Harris The neural basis of centre-surround interactions in visual motion processing Journal Article In: PLoS ONE, vol. 6, no. 7, pp. e22902, 2011. @article{Moutsiana2011,Perception of a moving visual stimulus can be suppressed or enhanced by surrounding context in adjacent parts of the visual field. We studied the neural processes underlying such contextual modulation with fMRI. We selected motion selective regions of interest (ROI) in the occipital and parietal lobes with sufficiently well defined topography to preclude direct activation by the surround. BOLD signal in the ROIs was suppressed when surround motion direction matched central stimulus direction, and increased when it was opposite. With the exception of hMT+/V5, inserting a gap between the stimulus and the surround abolished surround modulation. This dissociation between hMT+/V5 and other motion selective regions prompted us to ask whether motion perception is closely linked to processing in hMT+/V5, or reflects the net activity across all motion selective cortex. The motion aftereffect (MAE) provided a measure of motion perception, and the same stimulus configurations that were used in the fMRI experiments served as adapters. Using a linear model, we found that the MAE was predicted more accurately by the BOLD signal in hMT+/V5 than it was by the BOLD signal in other motion selective regions. However, a substantial improvement in prediction accuracy could be achieved by using the net activity across all motion selective cortex as a predictor, suggesting the overall conclusion that visual motion perception depends upon the integration of activity across different areas of visual cortex. |
Neil G. Muggleton; Roger Kalla; Chi-Hung Juan; Vincent Walsh Dissociating the contributions of human frontal eye fields and posterior parietal cortex to visual search Journal Article In: Journal of Neurophysiology, vol. 105, no. 6, pp. 2891–2896, 2011. @article{Muggleton2011,Imaging, lesion, and transcranial magnetic stimulation (TMS) studies have implicated a number of regions of the brain in searching for a target defined by a combination of attributes. The necessity of both frontal eye fields (FEF) and posterior parietal cortex (PPC) in task performance has been shown by the application of TMS over these regions. The effects of stimulation over these two areas have, thus far, proved to be remarkably similar and the only dissociation reported being in the timing of their involvement. We tested the hypotheses that 1) FEF contributes to performance in terms of visual target detection (possibly by modulation of activity in extrastriate areas with respect to the target), and 2) PPC is involved in translation of visual information for action. We used a task where the presence (and location) of the target was indicated by an eye movement. Task disruption was seen with FEF TMS (with reduced accuracy on the task) but not with PPC stimulation. When a search task requiring a manual response was presented, disruption with PPC TMS was seen. These results show dissociation of FEF and PPC contributions to visual search performance and that PPC involvement seems to be dependent on the response required by the task, whereas this is not the case for FEF. This supports the idea of FEF involvement in visual processes in a manner that might not depend on the required response, whereas PPC seems to be involved when a manual motor response to a stimulus is required. |
Sébastien Miellet; Roberto Caldara; Philippe G. Schyns Local jekyll and global hyde: The dual identity of face identification Journal Article In: Psychological Science, vol. 22, no. 12, pp. 1518–1526, 2011. @article{Miellet2011,The main concern in face-processing research is to understand the processes underlying the identification of faces. In the study reported here, we addressed this issue by examining whether local or global information supports face identification. We developed a new methodology called "iHybrid." This technique combines two famous identities in a gaze-contingent paradigm, which simultaneously provides local, foveated information from one face and global, complementary information from a second face. Behavioral face-identification performance and eye-tracking data showed that the visual system identified faces on the basis of either local or global information depending on the location of the observer's first fixation. In some cases, a given observer even identified the same face using local information on one trial and global information on another trial. A validation in natural viewing conditions confirmed our findings. These results clearly demonstrate that face identification is not rooted in a single, or even preferred, information-gathering strategy. |
Mark Mills; Andrew Hollingworth; Stefan Van der Stigchel; Lesa Hoffman; Michael D. Dodd Examining the influence of task set on eye movements and fixations Journal Article In: Journal of Vision, vol. 11, no. 8, pp. 1–15, 2011. @article{Mills2011,The purpose of the present study was to examine the influence of task set on the spatial and temporal characteristics of eye movements during scene perception. In previous work, when strong control was exerted over the viewing task via specification of a target object (as in visual search), task set biased spatial, rather than temporal, parameters of eye movements. Here, we find that more participant-directed tasks (in which the task establishes general goals of viewing rather than specific objects to fixate) affect not only spatial (e.g., saccade amplitude) but also temporal parameters (e.g., fixation duration). Further, task set influenced the rate of change in fixation duration over the course of viewing but not saccade amplitude, suggesting independent mechanisms for control of these parameters. |
Milica Milosavljevic; Christof Koch; Antonio Rangel Consumers can make decisions in as little as a third of a second Journal Article In: Judgment and Decision Making, vol. 6, no. 6, pp. 520–530, 2011. @article{Milosavljevic2011,We make hundreds of decisions every day, many of them extremely quickly and without much explicit deliberation. This motivates two important open questions: What is the minimum time required to make choices with above chance accuracy? What is the impact of additional decision-making time on choice accuracy? We investigated these questions in four experiments in which subjects made binary food choices using saccadic or manual responses, under either “speed” or “accuracy” instructions. Subjects were able to make above chance decisions in as little as 313 ms, and choose their preferred food item in over 70% of trials at average speeds of 404 ms. Further, slowing down their responses by either asking them explicitly to be confident about their choices, or to respond with hand movements, generated about a 10% increase in accuracy. Together, these results suggest that consumers can make accurate every-day choices, akin to those made in a grocery store, at significantly faster speeds than previously reported. |
Milica Milosavljevic; Eric Madsen; Christof Koch; Antonio Rangel Fast saccades toward numbers: Simple number comparisons can be made in as little as 230 ms Journal Article In: Journal of Vision, vol. 11, no. 4, pp. 1–12, 2011. @article{Milosavljevic2011a,Visual psychophysicists have recently developed tools to measure the maximal speed at which the brain can accurately carry out different types of computations (H. Kirchner & S. J. Thorpe, 2006). We use this methodology to measure the maximal speed with which individuals can make magnitude comparisons between two single-digit numbers. We find that individuals make such comparisons with high accuracy in 306 ms on average and are able to perform above chance in as little as 230 ms. We also find that maximal speeds are similar for "larger than" and "smaller than" number comparisons and in a control task that simply requires subjects to identify the number in a number-letter pair. The results suggest that the brain contains dedicated processes involved in implementing basic number comparisons that can be deployed in parallel with processes involved in low-level visual processing. |
David M. Milstein; Michael C. Dorris The relationship between saccadic choice and reaction times with manipulations of target value Journal Article In: Frontiers in Neuroscience, vol. 5, pp. 122, 2011. @article{Milstein2011,Choosing the option with the highest expected value (EV; reward probability × reward magnitude) maximizes the intake of reward under conditions of uncertainty. However, human economic choices indicate that our value calculation has a subjective component whereby probability and reward magnitude are not linearly weighted. Using a similar economic framework, our goal was to characterize how subjective value influences the generation of simple motor actions. Specifically, we hypothesized that attributes of saccadic eye movements could provide insight into how rhesus monkeys, a well-studied animal model in cognitive neuroscience, subjectively value potential visual targets. In the first experiment, monkeys were free to choose by directing a saccade toward one of two simultaneously displayed targets, each of which had an uncertain outcome. In this task, choices were more likely to be allocated toward the higher valued target. In the second experiment, only one of the two possible targets appeared on each trial. In this task, saccadic reaction times (SRTs) decreased toward the higher valued target. Reward magnitude had a much stronger influence on both choices and SRTs than probability, whose effect was observed only when reward magnitude was similar for both targets. Across EV blocks, a strong relationship was observed between choice preferences and SRTs. However, choices tended to maximize at skewed values whereas SRTs varied more continuously. Lastly, SRTs were unchanged when all reward magnitudes were 1×, 1.5×, and 2× their normal amount, indicating that saccade preparation was influenced by the relative value of the targets rather than the absolute value of any single-target. We conclude that value is not only an important factor( )for deliberative decision making in primates, but also for the selection and preparation of simple motor actions, such as saccadic eye movements. More precisely, our results indicate that, under conditions of uncertainty, saccade choices and reaction times are influenced by the relative expected subjective value of potential movements. |
Daniel Mirman; Eiling Yee; Sheila E. Blumstein; James S. Magnuson Theories of spoken word recognition deficits in Aphasia: Evidence from eye-tracking and computational modeling Journal Article In: Brain and Language, vol. 117, no. 2, pp. 53–68, 2011. @article{Mirman2011,We used eye-tracking to investigate lexical processing in aphasic participants by examining the fixation time course for rhyme (e.g., carrot-. parrot) and cohort (e.g., beaker-. beetle) competitors. Broca's aphasic participants exhibited larger rhyme competition effects than age-matched controls. A re-analysis of previously reported data (Yee, Blumstein, & Sedivy, 2008) confirmed that Wernicke's aphasic participants exhibited larger cohort competition effects. Individual-level analyses revealed a negative correlation between rhyme and cohort competition effect size across both groups of aphasic participants. Computational model simulations were performed to examine which of several accounts of lexical processing deficits in aphasia might account for the observed effects. Simulation results revealed that slower deactivation of lexical competitors could account for increased cohort competition in Wernicke's aphasic participants; auditory perceptual impairment could account for increased rhyme competition in Broca's aphasic participants; and a perturbation of a parameter controlling selection among competing alternatives could account for both patterns, as well as the correlation between the effects. In light of these simulation results, we discuss theoretical accounts that have the potential to explain the dynamics of spoken word recognition in aphasia and the possible roles of anterior and posterior brain regions in lexical processing and cognitive control. |
Parag K. Mital; Tim J. Smith; Robin L. Hill; John M. Henderson Clustering of gaze during dynamic scene viewing is predicted by motion Journal Article In: Cognitive Computation, vol. 3, no. 1, pp. 5–24, 2011. @article{Mital2011,Where does one attend when viewing dynamic scenes? Research into the factors influencing gaze location during static scene viewing have reported that low-level visual features contribute very little to gaze location especially when opposed by high-level factors such as viewing task. However, the inclusion of transient features such as motion in dynamic scenes may result in a greater influence of visual features on gaze allocation and coordination of gaze across viewers. In the present study, we investigated the contribution of low-to mid-level visual features to gaze location during free-viewing of a large dataset of videos ranging in content and length. Signal detection analysis on visual features and Gaussian Mixture Models for clustering gaze was used to identify the contribution of visual features to gaze location. The results show that mid-level visual features including corners and orientations can distinguish between actual gaze locations and a randomly sampled baseline. However, temporal features such as flicker, motion, and their respective contrasts were the most predictive of gaze location. Additionally, moments in which all viewers' gaze tightly clustered in the same location could be predicted by motion. Motion and mid-level visual features may influence gaze allocation in dynamic scenes, but it is currently unclear whether this influence is involuntary or due to correlations with higher order factors such as scene semantics. |
Holger Mitterer The mental lexicon is fully specified: Evidence from eye-tracking Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 37, no. 2, pp. 496–513, 2011. @article{Mitterer2011,Four visual-world experiments, in which listeners heard spoken words and saw printed words, compared an optimal-perception account with the theory of phonological underspecification. This theory argues that default phonological features are not specified in the mental lexicon, leading to asymmetric lexical matching: Mismatching input (pin) activates lexical entries with underspecified coronal stops (tin), but lexical entries with specified labial stops (pin) are not activated by mismatching input (tin). The eye-tracking data failed to show such a pattern. Although words that were phonologically similar to the spoken target attracted more looks than did unrelated distractors, this effect was symmetric in Experiment 1 with minimal pairs (tin-pin) and in Experiments 2 and 3 with words with an onset overlap (peacock-teacake). Experiment 4 revealed that /t/-initial words were looked at more frequently if the spoken input mismatched only in terms of place than if it mismatched in place and voice, contrary to the assumption that /t/ is unspecified for place and voice. These results show that speech perception uses signal-driven information to the fullest, as was predicted by an optimal perception account. |
Korbinian Moeller; Elise Klein; Hans-Christoph Nuerk (No) small adults: Children's processing of carry addition problems Journal Article In: Developmental Neuropsychology, vol. 36, no. 6, pp. 702–720, 2011. @article{Moeller2011,Analyses of eye-fixation data in adults suggested that the carry effect in addition is determined by the unit digits of the summands. Correspondingly, we recorded children's eye fixation behavior in a choice reaction paradigm. As for adults the carry effect was most pronounced on the unit digits of the summands. However, children's fixation pattern differed reliably from that of adults in other important aspects. While these data suggested common processes in children and adults for performing a carry in mental addition, children's eye fixation data indicated a less flexible processing style primarily based on calculating the correct result. |
Korbinian Moeller; Elise Klein; Hans-Christoph Nuerk Three processes underlying the carry effect in addition - Evidence from eye tracking Journal Article In: British Journal of Psychology, vol. 102, no. 3, pp. 623–645, 2011. @article{Moeller2011a,Recent research indicated that processes of unit-decade integration pose particular difficulty on multi-digit addition. In fact, longer response latencies as well as higher error rates have been observed for addition problems involving a carry operation (e.g., 18 +27) compared to problems not requiring a carry (e.g., 13 +32). However, the cognitive instantiation of this carry effect remained unknown. In the current study, this question was pursued by recording participants' eye fixation behaviour during addition problem verification. Analyses of the eye fixation data suggested a prominent role of the unit digits of the summands. The need for a carry seems to be recognized very early during the encoding of the problem after initial unit sum calculation has established the basis for the no carry/carry detection. Additionally, processes related to the actual carry execution seemed to be associated with the processing of the decade digit of the solution probe but were less unambiguous. Taken together, our findings indicate that unit-based calculations and the associated recognition that a carry is needed as well as its completion determine the difficulty of carry addition problems. On a more general level, this study shows how the nature of numerical-cognitive processes can be further differentiated by the evaluation of eye movement measures. |
Katie L. Meadmore; Itiel E. Dror; Romola S. Bucks; Simon P. Liversedge Eye movements during visuospatial judgements Journal Article In: European Journal of Cognitive Psychology, vol. 23, no. 1, pp. 92–101, 2011. @article{Meadmore2011,The goal of the current research was to determine whether eye movements reflect different underlying cognitive processes associated with visuospatial relation judgements. Ten participants made three different judgements regarding the position of a dot in relation to a bar; an above/below judgement, a near/far judgement, and a precise distance estimation. The results highlight similarities between above/ below and near/far visuospatial judgements; specifically, such binary judgements were fast, reflexive, and did not require precise distance computation. In contrast, estimating distance was comparatively cognitively demanding and required precise distance computation, as evidenced through distinct scan paths. The eye movement data provide significant insight into the cognitive processes underlying visuospatial judgements, showing aspects of visuospatial processing that are similar, as well as those that differ between tasks. |
Alberto Megías; Antonio Maldonado; Andrés Catena; Leandro Luigi Di Stasi; Jesús Serrano; Antonio Cándido Modulation of attention and urgent decisions by affect-laden roadside advertisement in risky driving scenarios Journal Article In: Safety Science, vol. 49, no. 10, pp. 1388–1393, 2011. @article{Megias2011,In road safety literature the effects of emotional content and salience of advertising billboards have been scarcely investigated. The main aim of this work was to uncover how affect-laden roadside advertisements can affect attention - eye-movements - and subsequent risky decisions - braking - on the Honda Riding Trainer motorcycle simulator. Results indicated that the number of fixations and total fixation time elicited by the negative and positive emotional advertisements were larger than the neutral ones. At the same time, negative pictures got later gaze disengagement than positive and neutral ones. This attentional capture results in less eye fixation times on the road relevant region, where the important driving events happen. Finally, the negative emotional valence advertisements sped up braking on subsequent risky situations. Overall results demonstrated how advertisements with emotional content modulate attention allocation and driving decisions in risky situations and might be helpful for designing roadside advertisements regulations and risk prevention programs. |
David Melcher; Manuela Piazza The role of attentional priority and saliency in determining capacity limits in enumeration and visual working memory Journal Article In: PLoS ONE, vol. 6, no. 12, pp. e29296, 2011. @article{Melcher2011,Many common tasks require us to individuate in parallel two or more objects out of a complex scene. Although the mechanisms underlying our abilities to count the number of items, remember the visual properties of objects and to make saccadic eye movements towards targets have been studied separately, each of these tasks require selection of individual objects and shows a capacity limit. Here we show that a common factor--salience--determines the capacity limit in the various tasks. We manipulated bottom-up salience (visual contrast) and top-down salience (task relevance) in enumeration and visual memory tasks. As one item became increasingly salient, the subitizing range was reduced and memory performance for all other less-salient items was decreased. Overall, the pattern of results suggests that our abilities to enumerate and remember small groups of stimuli are grounded in an attentional priority or salience map which represents the location of important items. |
Jorge Otero-Millan; Alessandro Serra; R. John Leigh; Xoana G. Troncoso; Stephen L. Macknik; Susana Martinez-Conde Distinctive features of saccadic intrusions and microsaccades in progressive supranuclear palsy Journal Article In: Journal of Neuroscience, vol. 31, no. 12, pp. 4379–4387, 2011. @article{OteroMillan2011a,The eyes do not stay perfectly still during attempted fixation; fixational eye movements and saccadic intrusions (SIs) continuously change the position of gaze. The most common type of SI, square-wave jerks (SWJs), consists of saccade pairs that appear purely horizontal on clinical inspection: the first saccade moves the eye away from the fixation target, and after a short interval, the second saccade brings it back toward the target. SWJs are prevalent in certain neurological disorders, including progressive supranuclear palsy (PSP). Here, we developed an objective method to identify SWJs. We found that SWJs are more frequent, larger, and more markedly horizontal in PSP patients than in healthy human subjects. Furthermore, the loss of a vertical component in fixational saccades and SWJs was the eye movement feature that best distinguished PSP patients from controls. We moreover determined that, in PSP patients and controls, the larger the saccade the more likely it was part of a SWJ. Furthermore, saccades produced by PSP patients had equivalent properties whether they were part of a SWJ or not, suggesting that normal fixational saccades (microsaccades) are rare in PSP. We propose that fixational saccades and SIs are generated by the same neural circuit and that, both in PSP patients and in controls, SWJs result from a coupling mechanism that generates a second corrective saccade shortly after a large fixation saccade. Because of brainstem and/or cerebellum impairment, fixational saccades in PSP are abnormally large and thus more likely to trigger a corrective saccade, giving rise to SWJs. |
Krista E. Overvliet; E. Azañón; S. Soto-Faraco Somatosensory saccades reveal the timing of tactile spatial remapping Journal Article In: Neuropsychologia, vol. 49, no. 11, pp. 3046–3052, 2011. @article{Overvliet2011,Remapping tactile events from skin to external space is an essential process for human behaviour. It allows us to refer tactile sensations to their actual externally based location, by combining anatomically based somatosensory information with proprioceptive information about the current body posture. We examined the time course of tactile remapping by recording speeded saccadic responses to somatosensory stimuli delivered to the hands. We conducted two experiments in which arm posture varied (crossed or uncrossed), so that anatomical and external frames of reference were either put in spatial conflict or were aligned. The data showed that saccade onset latencies in the crossed hands conditions were slower than in the uncrossed hands condition, suggesting that, in the crossed hands condition, remapping had to be completed before a correct saccade could be executed. Saccades to tactile stimuli when the hands were crossed were sometimes initiated to the wrong direction and then corrected in-flight, resulting in a turn-around saccade. These turn-around saccades were more likely to occur in short-latency responses, compared to onset latencies of saccades that went straight to target. The latter suggests that participants were postponing their saccade until the time the tactile event was represented according to the current body posture. We propose that the difference between saccade onset latencies of crossed and uncrossed hand postures, and between the onset of a turn-around saccade and a straight saccade in the crossed hand posture, reveal the timing of tactile spatial remapping. |
Müge Özbek; Markus Bindemann Exploring the time course of face matching: Temporal constraints impair unfamiliar face identification under temporally unconstrained viewing Journal Article In: Vision Research, vol. 51, no. 19, pp. 2145–2155, 2011. @article{Oezbek2011,The identification of unfamiliar faces has been studied extensively with matching tasks, in which observers decide if pairs of photographs depict the same person (identity matches) or different people (mismatches). In experimental studies in this field, performance is usually self-paced under the assumption that this will encourage best-possible accuracy. Here, we examined the temporal characteristics of this task by limiting display times and tracking observers' eye movements. Observers were required to make match/mismatch decisions to pairs of faces shown for 200, 500, 1000, or 2000. ms, or for an unlimited duration. Peak accuracy was reached within 2000. ms and two fixations to each face. However, intermixing exposure conditions produced a context effect that generally reduced accuracy on identity mismatch trials, even when unlimited viewing of faces was possible. These findings indicate that less than 2. s are required for face matching when exposure times are variable, but temporal constraints should be avoided altogether if accuracy is truly paramount. The implications of these findings are discussed. |
Adam Palanica; Roxane J. Itier Searching for a perceived gaze direction using eye tracking Journal Article In: Journal of Vision, vol. 11, no. 2, pp. 1–13, 2011. @article{Palanica2011,The purpose of the current study was to use eye tracking to better understand the “stare-in-the-crowd effect”—the notion that direct gaze is more easily detected than averted gaze in a crowd of opposite-gaze distractors. Stimuli were displays of four full characters aligned across the monitor (one target and three distractors). Participants completed a visual search task in which they were asked to detect the location of either a direct gaze or an averted gaze target. Reaction time (RT) results indicated faster responses to direct than averted gaze only for characters situated in the far peripheral visual fields. Eye movements confirmed a serial search strategy (definitely ruling out any pop-out effects) and revealed different exploration patterns between hemifields. The latency before the first fixation on target strongly correlated with response RTs. In the LVF, that latency was also faster for direct than averted gaze targets, suggesting that the response asymmetry in favor of direct gaze stemmed from faster direct gaze target detection. In the RVF, however, the response bias to direct gaze seemed not due to a faster visual detection but rather to a different cognitive mechanism. Direct gaze targets were also responded to even faster when their position was congruent with the direction of gaze of distractors. These findings suggest that the detection asymmetry for direct gaze is highly dependent on target position and influenced by social contexts. |
Sebastian Pannasch; Johannes Schulz; Boris M. Velichkovsky On the control of visual fixation durations in free viewing of complex images Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 4, pp. 1120–1132, 2011. @article{Pannasch2011,The mechanisms for the substantial variation in the durations of visual fixations in scene perception are not yet well understood. During free viewing of paintings, gaze-contingent irrelevant distractors (Exp. 1) and non-gaze-related time-locked display changes (Exp. 2) were presented. We demonstrated that any visual change-its onset and offset-prolongs the ongoing fixation (i.e., delays the following saccade), strongly suggesting that fixation durations are under the direct control of the stimulus information. The strongest influence of distraction was observed for fixations preceded by saccades within the parafoveal range (<5° of visual angle). We assume that these fixations contribute to the focal in contrast to the ambient mode of attention (Pannasch & Velichkovsky, Visual Cognition, 17, 1109-1131, 2009; Velichkovsky, Memory, 10, 405-419, 2002). Recent findings about two distinct "subpopulations of fixations," one under the direct and another under the indirect control of stimulation (e.g., Henderson & Smith, Visual Cognition, 17, 1055-1082, 2009), are reconsidered in view of these results. |
Muriel T. N. Panouillères; Christian Urquizar; Roméo Salemme; Denis Pélisson In: PLoS ONE, vol. 6, no. 2, pp. e17329, 2011. @article{Panouilleres2011,When goal-directed movements are inaccurate, two responses are generated by the brain: a fast motor correction toward the target and an adaptive motor recalibration developing progressively across subsequent trials. For the saccadic system, there is a clear dissociation between the fast motor correction (corrective saccade production) and the adaptive motor recalibration (primary saccade modification). Error signals used to trigger corrective saccades and to induce adaptation are based on post-saccadic visual feedback. The goal of this study was to determine if similar or different error signals are involved in saccadic adaptation and in corrective saccade generation. Saccadic accuracy was experimentally altered by systematically displacing the visual target during motor execution. Post-saccadic error signals were studied by manipulating visual information in two ways. First, the duration of the displaced target after primary saccade termination was set at 15, 50, 100 or 800 ms in different adaptation sessions. Second, in some sessions, the displaced target was followed by a visual mask that interfered with visual processing. Because they rely on different mechanisms, the adaptation of reactive saccades and the adaptation of voluntary saccades were both evaluated. We found that saccadic adaptation and corrective saccade production were both affected by the manipulations of post-saccadic visual information, but in different ways. This first finding suggests that different types of error signal processing are involved in the induction of these two motor corrections. Interestingly, voluntary saccades required a longer duration of post-saccadic target presentation to reach the same amount of adaptation as reactive saccades. Finally, the visual mask interfered with the production of corrective saccades only during the voluntary saccades adaptation task. These last observations suggest that post-saccadic perception depends on the previously performed action and that the differences between saccade categories of motor correction and adaptation occur at an early level of visual processing. |
Caroline Paquette; Joyce Fung Old age affects gaze and postural coordination Journal Article In: Gait and Posture, vol. 33, no. 2, pp. 227–232, 2011. @article{Paquette2011,Visual tracking of the surrounding environment is an important daily task, often executed simultaneously with the regulation of upright balance. Visual and postural coordination may be affected by aging which is associated with a decline in sensory and motor functions. The aim of the present study was to assess the effects of aging on the control of saccadic and smooth pursuit eye movements when standing on a moving surface. Nineteen young and 12 elderly subjects tracked a visual target presented as unpredictable smooth pursuit or saccadic displacements. Subjects were instructed to maintain gaze on target during quiet stance with or without yaw surface rotations. Elderly subjects followed both saccadic and pursuit targets with less accuracy than young subjects. Moreover, elderly subjects responded with longer time lags during saccadic target shifts and executed more catch-up saccades during smooth pursuits than younger subjects. Standing on a moving surface induced larger target-gaze errors. Catch-up saccades during pursuit occurred more frequently during surface perturbations. Our results suggest that visual tracking abilities decline with age and that postural challenge affects accuracy but not timing of gaze responses. Such declines observed with aging may result from multiple but minor sensory and motor deficits. |
Nhung X. Nguyen; Andrea Stockum; Gesa A. Hahn; Susanne Trauzettel-Klosinski Training to improve reading speed in patients with juvenile macular dystrophy: A randomized study comparing two training methods Journal Article In: Acta Ophthalmologica, vol. 89, no. 1, pp. 82–88, 2011. @article{Nguyen2011,Purpose: In this study, we examined the clinical application of two training methods for optimizing reading ability in patients with juvenile macular dystrophy with established eccentric preferred reti- nal locus and optimal use of low-vision aids. Method: This randomized study included 36 patients with juvenile macular dystrophy (35 with Stargardt's disease and one with Best's disease). All patients have been using individually opti- mized low-vision aids. After careful ophthalmological examination, patients were randomized into two groups: Group 1: Training to read during rapid serial visual presentation (RSVP) with elimination of eye movements as far as possible (n = 20); Group 2: Training to optimize reading eye movements (SM, sensomotoric training) (n = 16). Only patients with magnification requirement up to sixfold were included in the study. Training was performed for 4 weeks with an intensity of ½ hr per day and 5 days a week. Reading speed during page reading was measured before and after training. Eye movements during silent reading were recorded before and after training using a video eye tracker in 11 patients (five patients of SM and six of RSVP training group) and using an infrared reflection system in five patients (three patients from the SM and two patients of RSVP training group). Results: Age, visual acuity and magnification requirement did not differ significantly between the two groups. The median reading speed was 83 words per minute (wpm) (interquartile range 74–105 wpm) in the RSVP training group and 102 (interquartile range 63–126 wpm) in the SM group before training and increased significantly to 104 (interquartile range 81–124 wpm) and 122, respectively (interquartile range 102–137 wpm; p = 0.01 and 0.006) after training, i.e. patients with RSVP training increased their reading speed by a median of 21 wpm, while it was 20 wpm in the SM group. There were individual patients, who benefited strongly from the training. Eye move- ment recordings before and after training showed that in the RSVP group, increasing reading speed correlated with decreasing fixation duration (r = )0.75 |
Jianguang Ni; Huihui Jiang; Yixiang Jin; Nanhui Chen; Jianhong Wang; Zhengbo Wang; Yuejia Luo; Yuanye Ma; Xintian Hu Dissociable modulation of overt visual attention in valence and arousal revealed by topology of scan path Journal Article In: PLoS ONE, vol. 6, no. 4, pp. e18262, 2011. @article{Ni2011,Emotional stimuli have evolutionary significance for the survival of organisms; therefore, they are attention-grabbing and are processed preferentially. The neural underpinnings of two principle emotional dimensions in affective space, valence (degree of pleasantness) and arousal (intensity of evoked emotion), have been shown to be dissociable in the olfactory, gustatory and memory systems. However, the separable roles of valence and arousal in scene perception are poorly understood. In this study, we asked how these two emotional dimensions modulate overt visual attention. Twenty-two healthy volunteers freely viewed images from the International Affective Picture System (IAPS) that were graded for affective levels of valence and arousal (high, medium, and low). Subjects' heads were immobilized and eye movements were recorded by camera to track overt shifts of visual attention. Algebraic graph-based approaches were introduced to model scan paths as weighted undirected path graphs, generating global topology metrics that characterize the algebraic connectivity of scan paths. Our data suggest that human subjects show different scanning patterns to stimuli with different affective ratings. Valence salient stimuli (with neutral arousal) elicited faster and larger shifts of attention, while arousal salient stimuli (with neutral valence) elicited local scanning, dense attention allocation and deep processing. Furthermore, our model revealed that the modulatory effect of valence was linearly related to the valence level, whereas the relation between the modulatory effect and the level of arousal was nonlinear. Hence, visual attention seems to be modulated by mechanisms that are separate for valence and arousal. |
Robert Niebergall; Paul S. Khayat; Stefan Treue; Julio C. Martinez-Trujillo Expansion of MT neurons excitatory receptive fields during covert attentive tracking Journal Article In: Journal of Neuroscience, vol. 31, no. 43, pp. 15499–15510, 2011. @article{Niebergall2011,Primates can attentively track moving objects while keeping gaze stationary. The neural mechanisms underlying this ability are poorly understood. We investigated this issue by recording responses of neurons in area MT of two rhesus monkeys while they performed two different tasks. During the Attend-Fixation task, two moving random dot patterns (RDPs) translated across a screen at the same speed and in the same direction while the animals directed gaze to a fixation spot and detected a change in its luminance. During the Tracking task, the animals kept gaze on the fixation spot and attentively tracked the two RDPs to report a change in the local speed of one of the patterns' dots. In both conditions, neuronal responses progressively increased as the RDPs entered the neurons' receptive field (RF), peaked when they reached its center, and decreased as they translated away. This response profile was well described by a Gaussian function with its center of gravity indicating the RF center and its flanks the RF excitatory borders. During Tracking, responses were increased relative to Attend-Fixation, causing the Gaussian profiles to expand. Such increases were proportionally larger in the RF periphery than at its center, and were accompanied by a decrease in the trial-to-trial response variability (Fano factor) relative to Attend-Fixation. These changes resulted in an increase in the neurons' performance at detecting targets at longer distances from the RF center. Our results show that attentive tracking dynamically changes MT neurons' RF profiles, ultimately improving the neurons' ability to encode the tracked stimulus features. |
Robert Niebergall; Paul S. Khayat; Stefan Treue; Julio C. Martinez-Trujillo Multifocal attention filters targets from distracters within and beyond primate mt neurons' receptive field boundaries Journal Article In: Neuron, vol. 72, no. 6, pp. 1067–1079, 2011. @article{Niebergall2011a,Visual attention has been classically described as a spotlight that enhances the processing of a behaviorally relevant object. However, in many situations, humans and animals must simultaneously attend to several relevant objects separated by distracters. To account for this ability, various models of attention have been proposed including splitting of the attentional spotlight into multiple foci, zooming of the spotlight over a region of space, and switching of the spotlight among objects. We investigated this controversial issue by recording neuronal activity in visual area MT of two macaques while they attended to two translating objects that circumvented a third distracter object located inside the neurons' receptive field. We found that when the attended objects passed through or nearby the receptive field, neuronal responses to the distracter were either decreased or remained unaltered. These results demonstrate that attention can split into multiple spotlights corresponding to relevant objects while filtering out interspersed distracters. |
Tanja C. W. Nijboer; Gabriela Satris; Stefan Van Stigchel The influence of synesthesia on eye movements: No synesthetic pop-out in an oculomotor target selection task Journal Article In: Consciousness and Cognition, vol. 20, no. 4, pp. 1193–1200, 2011. @article{Nijboer2011,Recent research on grapheme-colour synesthesia has focused on whether visual attention is necessary to induce a synesthetic percept. The current study investigated the influence of synesthesia on overt visual attention during an oculomotor target selection task. Chromatic and achromatic stimuli were presented with one target among distractors (e.g. a '2' (target) among multiple '5's (distractors)). Participants executed an eye movement to the target. Synesthetes and controls showed a comparable target selection performance across conditions and a 'pop-out effect' was only seen in the chromatic condition. As a pop-out effect was absent for the synesthetes in the achromatic condition, a synesthetic element appears not to elicit a synesthetic colour, even when it is the target. The synesthetic percepts are not pre-attentively available to distinguish the synesthetic target from synesthetic distractors when elements are presented in the periphery. Synesthesia appears to require full recognition to bind form and colour. |
Andrey R. Nikolaev; Chie Nakatani; Gijs Plomp; Peter Jurica; Cees Leeuwen Eye fixation-related potentials in free viewing identify encoding failures in change detection Journal Article In: NeuroImage, vol. 56, no. 3, pp. 1598–1607, 2011. @article{Nikolaev2011,We considered the hypothesis that spontaneous dissociation between the direction of attention and eye movement causes encoding failure in change detection. We tested this hypothesis by analyzing eye fixation-related potentials (EFRP) at the encoding stage of a change blindness task; when participants freely inspect a scene containing an unmarked target region, in which a change will occur in a subsequent presentation. We measured EFRP amplitude prior to the execution of a saccade, depending on its starting or landing position relative to the target region. For those landings inside the target region, we found a difference in EFRP between correct detection and failure. Overall, correspondence between EFRP amplitude and the size of the saccade predicted successful detection of change; lack of correspondence was followed by change blindness. By contrast, saccade sizes and fixation durations around the target region were unrelated to subsequent change detection. Since correspondence between EFRP and eye movement indicates that overt attention was given to the target region, we concluded that overt attention is needed for successful encoding and that dissociation between eye movement and attention leads to change blindness. |
Shinji Nishimoto; Jack L. Gallant A three-dimensional spatiotemporal receptive field model explains responses of area MT neurons to naturalistic movies Journal Article In: Journal of Neuroscience, vol. 31, no. 41, pp. 14551–14564, 2011. @article{Nishimoto2011,Area MT has been an important target for studies of motion processing. However, previous neurophysiological studies of MT have used simple stimuli that do not contain many of the motion signals that occur during natural vision. In this study we sought to determine whether views of area MT neurons developed using simple stimuli can account for MT responses under more naturalistic conditions. We recorded responses from macaque area MT neurons during stimulation with naturalistic movies. We then used a quantitative modeling framework to discover which specific mechanisms best predict neuronal responses under these challenging conditions. We find that the simplest model that accurately predicts responses of MT neurons consists of a bank of V1-like filters, each followed by a compressive nonlinearity, a divisive nonlinearity, and linear pooling. Inspection of the fit models shows that the excitatory receptive fields of MT neurons tend to lie on a single plane within the three-dimensional spatiotemporal frequency domain, and suppressive receptive fields lie off this plane. However, most excitatory receptive fields form a partial ring in the plane and avoid low temporal frequencies. This receptive field organization ensures that most MT neurons are tuned for velocity but do not tend to respond to ambiguous static textures that are aligned with the direction of motion. In sum, MT responses to naturalistic movies are largely consistent with predictions based on simple stimuli. However, models fit using naturalistic stimuli reveal several novel properties of MT receptive fields that had not been shown in prior experiments. |
Yasuki Noguchi; Shinsuke Shimojo; Ryusuke Kakigi; Minoru Hoshiyama An integration of color and motion information in visual scene analyses Journal Article In: Psychological Science, vol. 22, no. 2, pp. 153–158, 2011. @article{Noguchi2011,To analyze complex scenes efficiently, the human visual system performs perceptual groupings based on various features (e.g., color and motion) of the visual elements in a scene. Although previous studies demonstrated that such groupings can be based on a single feature (e.g., either color or motion information), here we show that the visual system also performs scene analyses based on a combination of two features. We presented subjects with a mixture of red and green dots moving in various directions. Although the pairings between color and motion information were variable across the dots (e.g., one red dot moved upward while another moved rightward), subjects' perceptions of the color-motion pairings were significantly biased when the randomly paired dots were flanked by additional dots with consistent color-motion pairings. These results indicate that the visual system resolves local ambiguities in color-motion pairings using unambiguous pairings in surrounds, demonstrating a new type of scene analysis based on the combination of two featural cues. |
Lauri Nummenmaa; Jari K. Hietanen; Manuel G. Calvo; Jukka Hyönä Food catches the eye but not for everyone: A BMI-contingent attentional bias in rapid detection of nutriments Journal Article In: PLoS ONE, vol. 6, no. 5, pp. e19215, 2011. @article{Nummenmaa2011,An organism's survival depends crucially on its ability to detect and acquire nutriment. Attention circuits interact with cognitive and motivational systems to facilitate detection of salient sensory events in the environment. Here we show that the human attentional system is tuned to detect food targets among nonfood items. In two visual search experiments participants searched for discrepant food targets embedded in an array of nonfood distracters or vice versa. Detection times were faster when targets were food rather than nonfood items, and the detection advantage for food items showed a significant negative correlation with Body Mass Index (BMI). Also, eye tracking during searching within arrays of visually homogenous food and nonfood targets demonstrated that the BMI-contingent attentional bias was due to rapid capturing of the eyes by food items in individuals with low BMI. However, BMI was not associated with decision times after the discrepant food item was fixated. The results suggest that visual attention is biased towards foods, and that individual differences in energy consumption--as indexed by BMI--are associated with differential attentional effects related to foods. We speculate that such differences may constitute an important risk factor for gaining weight. |
Marcus R. Munafò; Nicole Roberts; Linda Bauld; Ute Leaonards Plain packaging increases visual attention to health warnings on cigarette packs in non-smokers and weekly smokers but not daily smokers Journal Article In: Addiction, vol. 106, pp. 1505–1510, 2011. @article{Munafo2011,AIMS: To assess the impact of plain packaging on visual attention towards health warning information on cigarette packs. DESIGN: Mixed-model experimental design, comprising smoking status as a between-subjects factor, and package type (branded versus plain) as a within-subjects factor. SETTING: University laboratory. PARTICIPANTS: Convenience sample of young adults, comprising non-smokers (n = 15), weekly smokers (n = 14) and daily smokers (n = 14). MEASUREMENTS: Number of saccades (eye movements) towards health warnings on cigarette packs, to directly index visual attention. FINDINGS: Analysis of variance indicated more eye movements (i.e. greater visual attention) towards health warnings compared to brand information on plain packs versus branded packs. This effect was observed among non-smokers and weekly smokers, but not daily smokers. CONCLUSION: Among non-smokers and non-daily cigarette smokers, plain packaging appears to increase visual attention towards health warning information and away from brand information. |
Marnix Naber; Stefan Frässle; Wolfgang Einhäuser Perceptual rivalry: Reflexes reveal the gradual nature of visual awareness Journal Article In: PLoS ONE, vol. 6, no. 6, pp. e20910, 2011. @article{Naber2011,Rivalry is a common tool to probe visual awareness: a constant physical stimulus evokes multiple, distinct perceptual interpretations (‘‘percepts'') that alternate over time. Percepts are typically described as mutually exclusive, suggesting that a discrete (all-or-none) process underlies changes in visual awareness. Here we follow two strategies to address whether rivalry is an all-or-none process: first, we introduce two reflexes as objective measures of rivalry, pupil dilation and optokinetic nystagmus (OKN); second, we use a continuous input device (analog joystick) to allow observers a gradual subjective report. We find that the ‘‘reflexes'' reflect the percept rather than the physical stimulus. Both reflexes show a gradual dependence on the time relative to perceptual transitions. Similarly, observers' joystick deflections, which are highly correlated with the reflex measures, indicate gradual transitions. Physically simulating wave-like transitions between percepts suggest piece-meal rivalry (i.e., different regions of space belonging to distinct percepts) as one possible explanation for the gradual transitions. Furthermore, the reflexes show that dominance durations depend on whether or not the percept is actively reported. In addition, reflexes respond to transitions with shorter latencies than the subjective report and show an abundance of short dominance durations. This failure to report fast changes in dominance may result from limited access of introspection to rivalry dynamics. In sum, reflexes reveal that rivalry is a gradual process, rivalry's dynamics is modulated by the required action (response mode), and that rapid transitions in perceptual dominance can slip away from awareness. |
Hironori Nakatani; Nicoletta Orlandi; Cees Van Leeuwen Precisely timed oculomotor and parietal EEG activity in perceptual switching Journal Article In: Cognitive Neurodynamics, vol. 5, no. 4, pp. 399–409, 2011. @article{Nakatani2011,Blinks and saccades cause transient interruptions of visual input. To investigate how such effects influence our perceptual state, we analyzed the time courses of blink and saccade rates in relation to perceptual switching in the Necker cube. Both time courses of blink and saccade rates showed peaks at different moments along the switching process. A peak in blinking rate appeared 1,000 ms prior to the switching responses. Blinks occurring around this peak were associated with subsequent switching to the preferred interpretation of the Necker cube. Saccade rates showed a peak 150 ms prior to the switching response. The direction of saccades around this peak was predictive of the perceived orientation of the Necker cube afterwards. Peak blinks were followed and peak saccades were preceded by transient parietal theta band activity indicating the changing of the perceptual interpretation. Precisely-timed blinks, therefore, can initiate perceptual switching, and precisely-timed saccades can facilitate an ongoing change of interpretation. textcopyright 2011 The Author(s). |
Nicole Naue; Daniel Strüber; Ingo Fründ; Jeanette Schadow; Daniel Lenz; Stefan Rach; Ursula Körner; Christoph S. Herrmann Gamma in motion: Pattern reversal elicits stronger gamma-band responses than motion Journal Article In: NeuroImage, vol. 55, no. 2, pp. 808–817, 2011. @article{Naue2011,Previous studies showed higher gamma-band responses (GBRs, ≈ 40. Hz) of the electroencephalogram (EEG) for moving compared to stationary stimuli. However, it is unclear whether this modulation by motion reflects a special responsiveness of the GBR to the stimulus feature ''motion,'' or whether GBR enhancements of similar magnitude can be elicited also by a salient change within a static stimulus that does not include motion.Therefore, we measured the EEG of healthy subjects watching stationary square wave gratings of high contrast that either started to move or reversed their black and white pattern shortly after their onset. The strong contrast change of the pattern reversal represented a salient but motionless change within the grating that was compared to the onset of the stationary grating and the motion onset. Induced and evoked GBRs were analyzed for all three display conditions. In order to assess the influenceof fixational eye movements on the induced GBRs, we also examined the time courses of microsaccade rates during the three display conditions. Amplitudes of both evoked and induced GBRs were stronger for pattern reversal than for motion onset. There was no significant amplitude difference between the onsets of the stationary and moving gratings. However, mean frequencies of the induced GBR were $sim$10. Hz higher in response to the onsets of moving compared to stationary gratings. Furthermore, the modulations of the induced GBR did not parallel the modulations of microsaccade rate, indicating that our induced GBRs reflect neuronal processes. These results suggest that, within the gamma-band range, the encoding of moving gratings in early visual cortex is primarily based on an upward frequency shift, whereas contrast changes within static gratings are reflected by amplitude enhancement. |
Mark B. Neider; Arthur F. Kramer Older adults capitalize on contextual information to guide search Journal Article In: Experimental Aging Research, vol. 37, no. 5, pp. 539–571, 2011. @article{Neider2011,Much has been learned about the age-related cognitive declines associated with the attentional processes that utilize perceptual features during visual search. However, questions remain regarding the ability of older adults to use scene information to guide search processes, perhaps as a compensatory mechanism for declines in perceptual processes. The authors had younger and older adults search pseudorealistic scenes for targets with strong or no spatial associations. Both younger and older adults exhibited reaction time benefits when searching for a target that was associated with a specific scene region. Eye movement analyses revealed that all observers dedicated most oftheir time to scanning target-consistent display regions and that guidance to these regions was often evident on the initial saccade ofa trial. Both the benefits and costs related to contextual information were larger for older adults, suggesting that this information was relied on heavily to guide search processes towards the target. |
Mark B. Neider; Gregory J. Zelinsky Cutting through the clutter: Searching for targets in evolving realistic scenes Journal Article In: Journal of Vision, vol. 11, no. 14, pp. 1–16, 2011. @article{Neider2011a,We evaluated the use of visual clutter as a surrogate measure of set size effects in visual search by comparing the effects of subjective clutter (determined by independent raters) and objective clutter (as quantified by edge count and feature congestion) using "evolving" scenes, ones that varied incrementally in clutter while maintaining their semantic continuity. Observers searched for a target building in rural, suburban, and urban city scenes created using the game SimCity. Stimuli were 30 screenshots obtained for each scene type as the city evolved over time. Reaction times and search guidance (measured by scan path ratio) were fastest/strongest for sparsely cluttered rural scenes, slower/weaker for more cluttered suburban scenes, and slowest/weakest for highly cluttered urban scenes. Subjective within-city clutter estimates also increased as each city matured and correlated highly with RT and search guidance. However, multiple regression modeling revealed that adding objective estimates failed to better predict search performance over the subjective estimates alone. This suggests that within-city clutter may not be explained exclusively by low-level feature congestion; conceptual congestion (e.g., the number of different types of buildings in a scene), part of the subjective clutter measure, may also be important in determining the effects of clutter on search. |
Olufunmilola Ogun; Jayalakshmi Viswanathan; Jason J. S. Barton The effect of central (macula) sparing of contralateral line bisection bias: A study with virtual hemianopia Journal Article In: Neuropsychologia, vol. 49, no. 12, pp. 3377–3382, 2011. @article{Ogun2011,Hemianopic patients show a contralesional bisection bias, but it is unclear whether this is a consequence of their field loss or related to extrastriate damage. One observation cited against the former is that hemianopic bisection bias does not vary with the degree of central (macular) sparing; however, it is unclear to what extent central sparing should affect this bias. Our goal was to determine the effect of central sparing on line bisection biases from field loss alone, with two approaches. First, we studied 12 healthy subjects viewing lines under conditions of virtual hemianopia, created by a gaze-contingent technique. Second, we calculated the effect predicted by a visuospatial model of the effect of central magnification on line representations in the visual system. Our results first replicated the contralateral line bisection bias with hemianopia, confirming that this can be generated by visual hemifield loss in the absence of extrastriate damage. Central sparing had only a modest effect on hemianopic bisection bias, with only slightly less bias with 10° compared to 2° of central sparing. In accordance with these empiric data, computing the center of mass for line representations in our model showed only a shallow decline in bisection bias as central sparing increased from 0 to 10°. We conclude that contralateral bisection bias only decreases slightly with central sparing, and that the absence of a statistically significant effect of central sparing in patients cannot be taken as evidence against a visual origin of contralateral hemianopic line bisection bias. |
Sven Ohl; Stephan A. Brandt; Reinhold Kliegl Secondary (micro-)saccades: The influence of primary saccade end point and target eccentricity on the process of postsaccadic fixation Journal Article In: Vision Research, vol. 51, no. 23-24, pp. 2340–2347, 2011. @article{Ohl2011,We examine how the size of saccadic under-/overshoot and target eccentricity influence the latency, amplitude and orientation of secondary (micro-)saccades. In our experiment, a target appeared at an eccentricity of either 6° or 14° of visual angle. Subjects were instructed to direct their gaze as quickly as possible to the target and hold fixation at the new location until the end of the trial. Typically, increasing saccadic error is associated with faster and larger secondary saccades. We show that secondary saccades at distant in contrast to close targets have in a specific error range a shorter latency, larger amplitude, and follow more often the direction of the primary saccade. Finally, we demonstrate that an undershooting primary saccade is followed almost exclusively by secondary saccades into the same direction while overshooting primary saccades are followed by secondary saccades into both directions. This supports the notion that under- and overshooting imply different consequences for postsaccadic oculomotor processing. Results are discussed using a model, introduced by Rolfs, Kliegl, and Engbert (2008), to account for the generation of microsaccades. We argue that the dynamic interplay of target eccentricity and the magnitude of the saccadic under-/overshoot can be explained by a different strength of activation in the two hemispheres of the saccadic motor map in this model. |
Anna Oleksiak; P. Christiaan Klink; Albert Postma; Ineke J. M. Ham; Martin J. Lankheet; Richard J. A. Wezel Spatial summation in macaque parietal area 7a follows a winner-take-all rule Journal Article In: Journal of Neurophysiology, vol. 105, no. 3, pp. 1150–1158, 2011. @article{Oleksiak2011,While neurons in posterior parietal cortex have been found to signal the presence of a salient stimulus among multiple items in a display, spatial summation within their receptive field in the absence of an attentional bias has never been investigated. This information, however, is indispensable when one investigates the mechanisms of spatial attention and competition between multiple visual objects. To examine the spatial summation rule in parietal area 7a neurons, we trained rhesus monkeys to fixate on a central cross while two identical stimuli were briefly displayed in a neuron's receptive field. The response to a pair of dots was compared with the responses to the same dots when they were presented individually. The scaling and power parameters of a generalized summation algorithm varied greatly, both across neurons and across combinations of stimulus locations. However, the averaged response of the recorded population of 7a neurons was consistent with a winner-take-all rule for spatial summation. A control experiment where a monkey covertly attended to both stimuli simultaneously suggests that attention introduces additional competition by facilitating the less optimal stimulus. Thus an averaging stage is introduced between ∼ 200 and 300 ms of the response to a pair of stimuli. In short, the summation algorithm over the population of area 7a neurons carries the signature of a winner-take-all operation, with spatial attention possibly influencing the temporal dynamics of stimulus competition, that is the moment that the "winner" takes "victory" over the "loser" stimulus. |
Bettina Olk; Yu Jin Effects of aging on switching the response direction of pro-and antisaccades Journal Article In: Experimental Brain Research, vol. 208, no. 1, pp. 139–150, 2011. @article{Olk2011,The present study investigated effects of task switching between pro- and antisaccades and switching the direction of these saccades (response switching) on performance of younger and older adults. Participants performed single-task blocks, in which only pro- or only antisaccades had to be made as well as mixed-task blocks, in which pro- and antisaccades were required. Analysis of specific task switch effects in the mixed-task blocks showed switch costs for error rates for prosaccades for both groups, suggesting that antisaccade task rules persisted and affected the following prosaccade. The comparison between single- and mixed-task blocks showed that mixing costs were either equal or smaller for older than younger participants, indicating that the older participants were well able to keep task sets in working memory. The most prominent age difference that was observed for response switching was that for the older but not younger group task switching and response switching interacted, resulting in less errors when two consecutive antisaccades were made in the same direction. This finding is best explained with a facilitation of these consecutive antisaccades. The present study clearly demonstrated the impact of response switching and a difference between age groups, underlining the importance of considering this factor when investigating pro- and antisaccades, especially antisaccades, and when investigating task switching and aging. |
Samantha C. Otero; Brendan S. Weekes; Samuel B. Hutton Pupil size changes during recognition memory Journal Article In: Psychophysiology, vol. 48, no. 10, pp. 1346–1353, 2011. @article{Otero2011,Pupils dilate to a greater extent when participants view old compared to new items during recognition memory tests. We report three experiments investigating the cognitive processes associated with this pupil old/new effect. Using a remember/know procedure, we found that the effect occurred for old items that were both remembered and known at recognition, although it was attenuated for known compared to remembered items. In Experiment 2, the pupil old/new effect was observed when items were presented acoustically, suggesting the effect does not depend on low-level visual processes. The pupil old/new effect was also greater for items encoded under deep compared to shallow orienting instructions, suggesting it may reflect the strength of the underlying memory trace. Finally, the pupil old/new effect was also found when participants falsely recognized items as being old. We propose that pupils respond to a strength-of-memory signal and suggest that pupillometry provides a useful technique for exploring the underlying mechanisms of recognition memory. |
Jorge Otero-Millan; Stephen L. Macknik; Apollo Robbins; Susana Martinez-Conde Stronger misdirection in curved than in straight motion Journal Article In: Frontiers in Human Neuroscience, vol. 5, pp. 133, 2011. @article{OteroMillan2011,Illusions developed by magicians are a rich and largely untapped source of insight into perception and cognition. Here we show that curved motion, as employed by the magician in a classic sleight of hand trick, generates stronger misdirection than rectilinear motion, and that this difference can be explained by the differential engagement of the smooth pursuit and the saccadic oculomotor systems. This research exemplifies how the magician's intuitive understanding of the spectator's mindset can surpass that of the cognitive scientist in specific instances, and that observation-based behavioral insights developed by magicians are worthy of quantitative investigation in the neuroscience laboratory. |
Ningdong Li; Xiajuan Wang; Yuchuan Wang; Liming Wang; Ming Ying; Ruifang Han; Yuyan Liu; Kanxing Zhao Investigation of the gene mutations in two Chinese families with X-linked infantile nystagmus Journal Article In: Molecular Vision, vol. 17, pp. 461–468, 2011. @article{Li2011,Purpose: To identify the gene mutations causing X-linked infantile nystagmus in two Chinese families (NYS003 and NYS008), of which the NYS003 family was assigned to the FERM domain–containing 7 (FRMD7) gene linked region in our previous study, and no mutations were found by direct sequencing. Methods: Two microsatellites, DXS1047 and DXS1001, were amplified using a PCR reaction for the linkage study in the NYS008 family. FRMD7 was sequenced and mutations were analyzed. Multiplex ligation-dependent probe amplification (MLPA) was used to detect FRMD7 mutations in the NYS003 family. Results: The NYS008 family yielded a maximum logarithm of odds (LOD) score of 1.91 at $theta$=0 with DXS1001. FRMD7 sequencing showed a nucleotide change of c. 623A>G in exon7 of the patients' FRMD7 gene, which was predicted to result in an H208R amino acid change. This novel mutation was absent in 100 normal Han Chinese controls. No FRMD7 gene mutations were detected by MLPA in the NYS003 family. Conclusions: We identified a novel mutation, c. 623A>G (p. H208R), in a Han Chinese family with infantile nystagmus. This mutation expands the mutation spectrum of FRMD7 and contributes to the research on the molecular pathogenesis of FRMD7. |
Xingshan Li; Pin Liu; Keith Rayner Eye movement guidance in Chinese reading: Is there a preferred viewing location? Journal Article In: Vision Research, vol. 51, pp. 1146–1156, 2011. @article{Li2011a,In this study, we examined eye movement guidance in Chinese reading. We embedded either a 2-character word or a 4-character word in the same sentence frame, and observed the eye movements of Chinese readers when they read these sentences. We found that when all saccades into the target words were considered that readers eyes tended to land near the beginning of the word. However, we also found that Chinese readers' eyes landed at the center of words when they made only a single fixation on a word, and that they landed at the beginning of a word when they made more than one fixation on a word. However, simulations that we carried out suggest that these findings cannot be taken to unambiguously argue for word-based saccade targeting in Chinese reading. We discuss alternative accounts of eye guidance in Chinese reading and suggest that eye movement target planning for Chinese readers might involve a combination of character-based and word-based targeting contingent on word segmentation processes. |
I. Fan Lin; Andrei Gorea Location and identity memory of saccade targets Journal Article In: Vision Research, vol. 51, no. 3, pp. 323–332, 2011. @article{Lin2011,While the memory of objects' identity and of their spatiotopic location may sustain transsaccadic spatial constancy, the memory of their retinotopic location may hamper it. Is it then true that saccades perturb retinotopic but not spatiotopic memory? We address this issue by assessing localization performances of the last and of the penultimate saccade target in a series of 2-6 saccades. Upon fixation, nine letter-pairs, eight black and one white, were displayed at 3° eccentricity around fixation within a 20°×20° grey frame, and subjects were instructed to saccade to the white letter-pair; the cycle was then repeated. Identical conditions were run with the eyes maintaining fixation throughout the trial but with the grey frame moving so as to mimic its retinal displacement when the eyes moved. At the end of a trial, subjects reported the identity and/or the location of the target in either retinotopic (relative to the current fixation dot) or frame-based. 1In the context of this study " frame-based" and " spatiotopic" are equivalent terms and will be used interchangeably.1(relative to the grey frame) coordinates. Saccades degraded target's retinotopic location memory but not its frame-based location or its identity memory. Results are compatible with the notion that spatiotopic representation takes over retinotopic representation during eye movements thereby contributing to the stability of the visual world as its retinal projection jumps on our retina from saccade to saccade. |
Alexander Maier; Christopher J. Aura; David A. Leopold Infragranular sources of sustained local field potential responses in macaque primary visual cortex Journal Article In: Journal of Neuroscience, vol. 31, no. 6, pp. 1971–1980, 2011. @article{Maier2011,A local field potential (LFP) response can be measured throughout the visual cortex in response to the abrupt appearance of a visual stimulus. Averaging LFP responses to many stimulus presentations isolates transient, phase-locked components of the response that are consistent from trial to trial. However, stimulus responses are also composed of sustained components, which differ in their phase from trial to trial and therefore must be evaluated using other methods, such as computing the power of the response of each trial before averaging. Here, we investigate the basis of phase-locked and non-phase-locked LFP responses in the primary visual cortex of the macaque monkey using a novel variant of current source density (CSD) analysis. We applied a linear array of electrode contacts spanning the thickness of the cortex to measure the LFP and compute band-limited CSD power to identify the laminar sites of persistent current exchange that may be the basis of sustained visual LFP responses. In agreement with previous studies, we found a short-latency phase-locked current sink, thought to correspond to thalamocortical input to layer 4C. In addition, we found a prominent non-phase-locked component of the CSD that persisted as long as the stimulus was physically present. The latter was relatively broadband, lasted throughout the stimulus presentation, and was centered ∼500 $mu$m deeper than the initial current sink. These findings demonstrate a fundamental difference in the neural mechanisms underlying the initial and sustained processing of simple visual stimuli in the V1 microcircuit. |
Femke Maij; Eli Brenner; Jeroen B. J. Smeets Peri-saccadic mislocalization is not influenced by the predictability of the saccade target location Journal Article In: Vision Research, vol. 51, no. 1, pp. 154–159, 2011. @article{Maij2011,Flashes presented around the time of a saccade are often mislocalized. The precise pattern of mislocalization is influenced by many factors. Here we study one such factor: the predictability of the saccade target's location. The experiment examines two conditions. In the first the subject makes the same horizontal rightward saccade to the same target location over and over again. In the second the subject makes saccades to a target that is jumping in unpredictable radial directions. A dot is flashed in the vicinity of the saccade target near the time of saccade onset. Subjects are asked to localize the flash by touching its location on the screen. Although various saccade parameters differed, the errors that subjects made were very similar in both conditions. We conclude that the pattern of mislocalization does not depend on the predictability of the location of the saccade target. |
Femke Maij; Eli Brenner; Jeroen B. J. Smeets Temporal uncertainty separates flashes from their background during saccades Journal Article In: Journal of Neuroscience, vol. 31, no. 10, pp. 3708–3711, 2011. @article{Maij2011a,It is known that spatial localization of flashed objects fails around the time of rapid eye movements (saccades). This mislocalization is often interpreted in terms of a combination of shifts and deformations of the brain's representation of space to account for the eye movement. Such temporary remapping of positions in space should affect all elements in a scene, leaving ordinal relationships between positions intact. We performed an experiment in which we presented flashes on a background with red and green regions to human subjects. We found that flashes that were presented on the green part of the background around the time of a saccade were readily reported to have been presented on the red part of the background and vice versa. This is inconsistent with the notion of a temporary shift and deformation of perceived space. To explain our results, we present a model that illustrates how temporal uncertainty could give rise to the observed spatial mislocalization. The model combines uncertainty about the time of the flash with a bias to localize targets where one is looking. It reproduced the pattern of mislocalization very accurately, showing that perisaccadic mislocalization can best be explained in terms of temporal uncertainty about the moment of the flash. |
Alexis D. J. Makin; Rochelle Ackerley; Kelly S. Wild; Ellen Poliakoff; Emma Gowen; Wael El-Deredy Coherent illusory contours reduce microsaccade frequency Journal Article In: Neuropsychologia, vol. 49, no. 9, pp. 2798–2801, 2011. @article{Makin2011,Synchronized high-frequency gamma band oscillations (30-100. Hz) are thought to mediate the binding of single visual features into whole-object representations. For example, induced gamma band oscillations (iGBRs) have been recorded ∼280. ms after the onset of a coherent Kanizsa triangle, but not after an incoherent equivalent shape. However, several recent studies have provided evidence that the EEG-recorded iGBR may be a by-product of small saccadic eye movements (microsaccades). Considering these two previous findings, one would hypothesis that there should be more microsaccades following the onset of a coherent Kanizsa triangle. However, we found that microsaccade rebound rate was significantly higher after an incoherent triangle was presented. This result suggests that microsaccades are not a reliable indicator of perceptual binding, and, more importantly, implies that iGBR cannot be universally produced by ocular artefacts. |
Mauro Marchitto; Leandro Luigi Di Stasi; José J. Cañas Ocular movements under taskload manipulations: Influence of geometry on saccades in air traffic control simulated tasks Journal Article In: Human Factors and Ergonomics in Manufacturing & Service Industries, vol. 19, no. 6, pp. 1–13, 2011. @article{Marchitto2011,Traffic geometry is a factor that contributes to cognitive complexity in air traffic control. In conflict-detection tasks, geometry can affect the attentional effort necessary to correctly perceive and interpret the situation; online measures of situational workload are therefore highly desirable. In this study, we explored whether saccadic movements vary with changes in geometry. We created simple scenarios with two aircraft and simulated a conflict detection task. Independent variables were the conflict angle and the distance to convergence point. We hypothesized lower saccadic peak velocity (and longer duration) for increasing complexity, that is, for increasing conflict angles and for different distances to convergence point. Response times varied accordingly with task complexity. Concerning saccades, there was a decrease of peak velocity (and a related increase of duration) for increased geometry complexity for large saccades (>15°). The data therefore suggest that geometry is able to influence "reaching" saccades and not "fixation" saccades. |
Andrea E. Martin; Brian McElree Direct-access retrieval during sentence comprehension: Evidence from Sluicing Journal Article In: Journal of Memory and Language, vol. 64, no. 4, pp. 327–343, 2011. @article{Martin2011,Language comprehension requires recovering meaning from linguistic form, even when the mapping between the two is indirect. A canonical example is ellipsis, the omission of information that is subsequently understood without being overtly pronounced. Comprehension of ellipsis requires retrieval of an antecedent from memory, without prior prediction, a property which enables the study of retrieval in situ (Martin & McElree, 2008, 2009). Sluicing, or inflectional-phrase ellipsis, in the presence of a conjunction, presents a test case where a competing antecedent position is syntactically licensed, in contrast with most cases of nonadjacent dependency, including verb-phrase ellipsis. We present speed-accuracy tradeoff and eye-movement data inconsistent with the hypothesis that retrieval is accomplished via a syntactically guided search, a particular variant of search not examined in past research. The observed timecourse profiles are consistent with the hypothesis that antecedents are retrieved via a cue-dependent direct-access mechanism susceptible to general memory variables. |
Chia-Lun Liu; Philip Tseng; Hui-Yen Chiau; Wei-Kuang Liang; Daisy L. Hung; Ovid J. L. Tzeng; Neil G. Muggleton; Chi-Hung Juan The location probability effects of saccade reaction times are modulated in the frontal eye fields but not in the supplementary eye field Journal Article In: Cerebral Cortex, vol. 21, no. 6, pp. 1416–1425, 2011. @article{Liu2011c,The visual system constantly utilizes regularities that are embedded in the environment and by doing so reduces the computational burden of processing visual information. Recent findings have demonstrated that probabilistic information can override attentional effects, such as the cost of making an eye movement away from a visual target (antisaccade cost). The neural substrates of such probability effects have been associated with activity in the superior colliculus (SC). Given the immense reciprocal connections to SC, it is plausible that this modulation originates from higher oculomotor regions, such as the frontal eye field (FEF) and the supplementary eye field (SEF). To test this possibility, the present study employed theta burst transcranial magnetic stimulation (TMS) to selectively interfere with FEF and SEF activity. We found that TMS disrupted the effect of location probability when TMS was applied over FEF. This was not observed in the SEF TMS condition. Together, these 2 experiments suggest that the FEF plays a critical role not only in initiating saccades but also in modulating the effects of location probability on saccade production. |
Donglai Liu; Yonghui Wang; Xiaolin Zhou Lexical- and perceptual-based object effects in the two-rectangle cueing paradigm Journal Article In: Acta Psychologica, vol. 138, no. 3, pp. 397–404, 2011. @article{Liu2011d,Previous studies demonstrate that attentional selection can be object-based, in which the object is defined in terms of Gestalt principles or lexical organizations. Here we investigate how attentional selection functions when the two types of objects are manipulated jointly. Experiment 1 replicated Li and Logan (2008) by showing that attentional shift between two Chinese characters is more efficient when they form a compound word than when they form a nonword. Experiment 2A presented characters either alone or within rectangles (Egly, Driver, & Rafal, 1994) and the characters in a rectangle formed either a word or a nonword. Experiment 2B differed from Experiment 2A in that the two characters forming a word were in different rectangles. Experiment 3A presented the two characters of a word either within a rectangle or in different rectangles. Experiment 3B used the same design as Experiment 3A but presented stimuli of different types in random orders, rather than in blocks as in Experiments 2A, 2B and 3A. In blocked presentation, detection responses to the target color on a character were faster when this character and the cue character formed a word than when they did not, and the size of this lexical-based object effect did not vary according to whether the two characters were presented alone or within or between rectangles. In random presentation, however, the lexical-based object effect was diminished when the two characters of a word were presented in different rectangles. Overall, these findings suggest that the processes that constrain attention deployment over conjoined objects can be strategically adjusted. |
Haoxue Liu; Guangming Ding; Weihua Zhao; Hui Wang; Kaizheng Liu; Ludan Shi Variation of drivers' visual features in long-tunnel entrance section on expressway Journal Article In: Journal of Transportation Safety and Security, vol. 3, no. 1, pp. 27–37, 2011. @article{Liu2011e,To avoid traffic accidents in long tunnel entrance sections, the authors studied the variation of driver's visual features based on real road experiments on the expressway. Drivers' visual feature parameters were recorded in real-time using Eyelink (eye tracking system) during the driving test. Mathematic models of drivers' fixation duration, the number of fixations, and saccade amplitude in tunnel entrance were established based on BP Neural Network (Error Back Propagation Network) simulation. Results showed that fixation duration increased gradually as the vehicle moving closer to the tunnel entrance, whereas the number of fixations and saccade amplitude decreased. Meanwhile, drivers' fixations shifted from straight ahead to the right side, which resulted in the number of fixations on the right side increased. After drivers entering the tunnel, fixation duration firstly decreased and then increased afterward, while the number of fixations and saccade amplitude kept increasing. |
Taosheng Liu; Luke Hospadaruk; David C. Zhu; Justin L. Gardner Feature-specific attentional priority signals in human cortex Journal Article In: Journal of Neuroscience, vol. 31, no. 12, pp. 4484–4495, 2011. @article{Liu2011f,Human can flexibly attend to a variety of stimulus dimensions, including spatial location and various features such as color and direction of motion. Although the locus of spatial attention has been hypothesized to be represented by priority maps encoded in several dorsal frontal and parietal areas, it is unknown how the brain represents attended features. Here we examined the distribution and organization of neural signals related to deployment of feature-based attention. Subjects viewed a compound stimulus containing two superimposed motion directions (or colors) and were instructed to perform an attention-demanding task on one of the directions (or colors). We found elevated and sustained functional magnetic resonance imaging response for the attention task compared with a neutral condition, without reliable differences in overall response amplitude between attending to different features. However, using multivoxel pattern analysis, we were able to decode the attended feature in both early visual areas (primary visual cortex to human motion complex hMT+) and frontal and parietal areas (e.g., intraparietal sulcus areas IPS1-IPS4 and frontal eye fields) that are commonly associated with spatial attention. Furthermore, analysis of the classifier weight maps showed that attending to motion and color evoked different patterns of activity, suggesting that different neuronal subpopulations in these regions are recruited for attending to different feature dimensions. Thus, our finding suggests that, rather than a purely spatial representation of priority, frontal and parietal cortical areas also contain multiplexed signals related to the priority of different nonspatial features. |
Taosheng Liu; Youyang Hou Global feature-based attention to orientation. Journal Article In: Journal of Vision, vol. 11, no. 10, pp. 1–8, 2011. @article{Liu2011a,Selective attention to motion direction can modulate the strength of direction-selective sensory responses regardless of their spatial locations. Although such spatially global modulation is thought to be a general property of feature-based attention, few studies have examined visual features other than motion. Here, we used an adaptation protocol combined with attentional instructions to assess whether attention to orientation, a prominent feature in early visual processing, also exhibit such spatially global modulation. We adapted observers to an orientation by cuing them to attend to the orientation in a compound grating that was presented at a peripheral location. We then assessed the size of the tilt aftereffect at three locations that were never stimulated by the adapter. Attending to orientation produced a tilt aftereffect in these locations, indicating that attention modulated orientation-selective mechanisms in remote locations from the adapter. Furthermore, there was no difference in the magnitude of the tilt aftereffect for test stimuli that were located at different distances and hemifields to the adapter. These results suggest that attention to orientation spreads uniformly across the visual field. Thus, spatially global modulation seems to be a general property of feature-based attention, and it provides a flexible mechanism to modulate feature salience across the visual field. |