EyeLink fMRI / MEG Publications
All EyeLink fMRI and MEG research publications (with concurrent eye tracking) up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Visual Cortex, Neural Plasticity, MEG, etc. You can also search for individual author names. If we missed any EyeLink fMRI or MEG articles, please email us!
2005 |
Brian Sullivan; Jelena Jovancevic; Mary Hayhoe; Gwen Sterns Use of gaze in natural tasks in Stargardt's disease: A preferred retinal region Journal Article In: International Congress Series, vol. 1282, pp. 608–612, 2005. @article{Sullivan2005, Use of a preferred retinal locus (PRL) in patients with central scotomas has been extensively investigated in reading. However, less is know about how consistently a PRL is used in ordinary behavior, where high resolution may not always be needed. We investigated eye movements of a Stargardt's disease patient, with bilateral central scotomas, in three tasks in both real and virtual environments. While making a sandwich, the subject predominantly located the object being manipulated in the lower left visual field, scattered over a 20° × 30° region. While catching a ball our subject positioned the ball in the lower left visual quadrant and also exhibited pursuit eye movements driven by the peripheral retina. While walking in a virtual environment, the patient did not use a PRL but instead centered gaze on pedestrians, whose vertical extent surpassed the boundaries of the scotoma. In the natural tasks studied the PRL is very broadly defined and depends on the resolution required for the task. We therefore suggest use of the term "preferred retinal region". |
Keith Rayner; Rebecca L. Johnson Letter-by-letter acquired dyslexia is due to the serial encoding of letters Journal Article In: Psychological Science, vol. 16, no. 7, pp. 530–534, 2005. @article{Rayner2005, Letter-by-letter acquired dyslexia (pure alexia) is assumed to be related to the serial encoding of letters, but the evidence for this assumption is somewhat indirect. Here, we demonstrate that the deficit is indeed due to serial encoding by comparing the performance of a letter-by-letter dyslexic reader with the performance of normal readers who were forced to read letter by letter; the data patterns are remarkably similar. |
Angela Rees; Stamatina A. Kabanarou; Louise E. Culham; Gary S. Rubin Can retinal eccentricity predict visual acuity and contrast sensitivity at the PRL in AMD patients? Journal Article In: International Congress Series, vol. 1282, pp. 694–698, 2005. @article{Rees2005, Most patients with age-related macular degeneration (AMD) and bilateral central scotomas adopt a preferred retinal locus (PRL) for eccentric viewing. It is postulated that the optimal PRL position is inferior visual space as it provides a larger uninterrupted visual span for reading and mobility. However, the majority of patients place their PRL to the left of their scotoma in visual field space. The purpose of this study was to investigate which factors determine PRL location and specifically, whether the PRL develops in the area of peripheral retina with best visual acuity (VA) and contrast sensitivity (CS). 24 patients were recruited. They were tested on a scanning laser ophthalmoscope to identify the PRL in their better eye. An eyetracker was used to assess peripheral VA and CS. In 19 patients, the PRL was located near the area of best VA. In only 11 patients, the PRL was located near the area of best CS. Patients had worse VA and CS at their PRLs compared to normal vision subjects. VA was best near the PRL, but this was not the case for CS. We cannot distinguish whether the PRL develops at the area of best VA or if it improves at the PRL through practice. |
Stefan Hawelka; Heinz Wimmer Impaired visual processing of multi-element arrays is associated with increased number of eye movements in dyslexic reading Journal Article In: Vision Research, vol. 45, no. 7, pp. 855–863, 2005. @article{Hawelka2005, For assessing simultaneous visual processing in dyslexic and normal readers a multi-element processing task was used which required the report of a single digit of briefly presented multi-digit arrays. Dyslexic readers exhibited higher recognition thresholds on 4- and 6-digit, but not on 2-digit arrays. Individual recognition thresholds on the multi-digit arrays were associated with number of eye movements during reading. The dyslexic multi-element processing deficit was not accompanied by deficient coherent motion detection or deficient visual precedence detection and was independent from deficits in phonological awareness and rapid naming. However, only about half of the dyslexic readers exhibited a multi-element processing deficit. |
Stamatina A. Kabanarou; C. Bellmann; Michael D. Crossland; Angela Rees; Mary P. Feely; Louise E. Culham; Gary S. Rubin Binocular versus monocular viewing in patients with age-related macular degeneration Journal Article In: International Congress Series, vol. 1282, pp. 613–616, 2005. @article{Kabanarou2005, This paper compares monocular versus binocular viewing in AMD patients during fixation and the potential of binocular function. Twenty-seven patients with bilateral AMD were recruited. A scanning laser ophthalmoscope was used to identify PRLs and map retinal scotomas monocularly. An infrared eye tracker was used to evaluate gaze position changes (and indirectly retinal locus changes) between monocular and binocular fixation. Through their combined use the retinal loci used for fixation under binocular viewing conditions were identified. Binocular function was tested with Bagolini striated glasses and fusion at the PRLs was tested with a computer-driven display. It was found that only five patients used the same PRL to fixate under monocular and binocular conditions for both eyes. 44.4% of the patients with symmetrical scotomas but only one patient with asymmetrical scotomas showed no shift in gaze position. However, there was no difference between them (chi-square |
Willem P. A. Kelders; Gert Jan Kleinrensink; J. N. Van Der Geest; Inger B. Schipper; Louw Feenstra; Chris I. De Zeeuw; Maarten A. Frens The cervico-ocular reflex is increased in whiplash injury patients Journal Article In: Journal of Neurotrauma, vol. 22, no. 1, pp. 133–137, 2005. @article{Kelders2005, Whiplash-associated disorders (WAD) are a major problem in the Western world, which put a formidable financial burden on modern society and which evoke an emerging debate on the true nature of their origin. To date there is no generally accepted test that allows us to diagnose WAD objectively. Because whiplash injury causes dysfunction of proprioception in the neck, we investigated the characteristics of the cervico-ocular reflex (COR) of presumptive WAD patients. These patients and age-matched healthy controls were rotated at different stimulus peak velocities in the dark while their head was fixed in space. The gain values of the COR were significantly increased in the patient population at a wide range of stimulus peak velocities with maximum difference at the lower frequencies (p = 0.037, ANOVA). Hence, although larger numbers of patients should be measured, the COR gain appears to be a parameter that may permit an objective diagnosis of WAD. |
Christian Bellebaum; Irene Daum; B. Koch; M. Schwarz; Klaus-Peter Hoffmann The role of the human thalamus in processing corollary discharge Journal Article In: Brain, vol. 128, no. 5, pp. 1139–1154, 2005. @article{Bellebaum2005, Corollary discharge signals play an important role in monitoring self-generated movements to guarantee spatial constancy. Recent work in macaques suggests that the thalamus conveys corollary discharge information of upcoming saccades passing from the superior colliculus to the frontal eye field. The present study aimed to investigate the involvement of the thalamus in humans by assessing the effect of thalamic lesions on the processing of corollary discharge information. Thirteen patients with selective thalamic lesions and 13 healthy age-matched control subjects performed a saccadic double-step task in which retino-spatial dissonance was induced, i.e. the retinal vector of the second target and the movement vector of the second saccade were different. Thus, the subjects could not rely on retinal information alone, but had to use corollary discharge information to correctly perform the second saccade. The amplitudes of first and second saccades were significantly smaller in patients than in controls. Five thalamic lesion patients showed unilateral deficits in using corollary discharge information, as revealed by asymmetries compared with the other patients and controls. Three patients with lateral thalamic lesions including the ventrolateral nucleus (VL) were impaired contralaterally to the side of damage and one patient with a lesion in the mediodorsal thalamus (MD) was impaired ipsilaterally to the lesion. The largest asymmetry was found in a patient with a bilateral thalamic lesion. The results provide evidence for a thalamic involvement in the processing of corollary discharge information in humans, with a potential role of both the VL and MD nuclei |
Shery Thomas; P. Crilehley; M. Lawden; S. Farooq; A. Thomas; Frank A. Proudlock; Cris S. Constantinescu; I. Gottlob Stiff person syndrome with eye movement abnormality, myasthenia gravis, and thymoma Journal Article In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 76, no. 1, pp. 141–142, 2005. @article{Thomas2005, Stiff person syndrome with eye movement abnormality, myasthenia gravis, and thymoma Stiff person syndrome (SPS) is a rare disorder of the central nervous system characterised by progressive fluctuating rigidity and painful spasms of the body musculature. We describe a patient with SPS with positive glutamic acid decarboxylase (GAD) antibodies who developed diplopia. Thymoma was detected by computed tomography (CT), and after thymectomy his symptoms improved. One month after thymectomy, he tested posi- tive for antiacetylcholine receptor (AchR) antibodies. |
Michael D. Crossland; Louise E. Culham; Stamatina A. Kabanarou; Gary S. Rubin Preferred retinal locus development in patients with macular disease Journal Article In: Ophthalmology, vol. 112, no. 9, pp. 1579–1585, 2005. @article{Crossland2005, Objective: To observe the development of the preferred retinal locus (PRL) in a group of patients with central scotomas caused by recent onset macular disease (MD). Design: Prospective observational case series. Participants: Twenty-five individuals with bilateral central scotomas caused by MD. All patients had experienced visual loss in their better eye in the 2 weeks before recruitment. Methods: Patients were assessed at baseline and at 4 further visits for up to 12 months. At each visit, the retinal area used for fixation was assessed using a scanning laser ophthalmoscope, the infrared Gazetracker was used to determine the number of discrete retinal areas used for fixation in 5 positions of gaze, and reading speed was measured using MN-Read-style sentences. Results: All 25 patients developed a PRL within 6 months. Sixteen patients (64%) made an adaptation whereby they were unaware of using an eccentric retinal area for fixation. Multiple fixation loci were exhibited by 11 patients at the end of the study. Nineteen patients used a consistent number of PRLs under all positions of gaze. Reading speed was not associated with PRL location or the presence of multiple PRLs. Conclusions: All of the patients in this study developed a repeatable preferred retinal locus within 6 months of visual loss in their second affected eye. Reading performance was better in patients who were not aware of using eccentric viewing strategies and who used a repeatable number of PRLs under all positions of gaze. These findings are relevant for counseling patients with MD and for the design of rehabilitation programs for patients with central vision loss. |
Michael D. Crossland; Louise E. Culham; Gary S. Rubin Reading speed and the perceptual span in patients with macular disease Journal Article In: International Congress Series, vol. 1282, pp. 498–501, 2005. @article{Crossland2005a, This presentation describes the results of a longitudinal assessment of the perceptual span, eye movements and reading speed in a group of patients with macular disease (MD). Eighteen patients with MD were recruited. All patients had developed a scotoma in their second affected eye in the 2 weeks prior to recruitment. Patients were assessed within 2 weeks of recruitment and again 3-12 months later. Eye movements were recorded whilst reading MN-Read style sentences using an infra-red gazetracker. Perceptual span was closely related to reading speed at the first (r2= 0.53, p < 0.001) and the second visit (r2= 0.72, p < 0.0001). In some patients the perceptual span changed by as much as two letters. Changes in the perceptual span were strongly related to change in reading speed (r2= 0.43, p < 0.005). These results lend support to the hypothesis that a reduced perceptual span is one cause of impaired reading in patients with macular disease. These results are relevant to the development of rehabilitation and training programs for patients with macular disease. |
Sabira K. Mannan; Dominic J. Mort; Timothy L. Hodgson; Jon Driver; Christopher Kennard; Masud Husain Revisiting previously searched locations in visual neglect: Role of right parietal and frontal lesions in misjudging old locations as new Journal Article In: Journal of Cognitive Neuroscience, vol. 17, no. 2, pp. 340–354, 2005. @article{Mannan2005, Right-hemisphere patients with left neglect often demonstrate abnormal visual search, re-examining stimuli to the right while ignoring those to the left. But re-fixations alone do not reveal if patients misjudge whether they have searched a location before. Here, we not only tracked the eye movements of 16 neglect patients during search, but also asked them to click a response button only when they judged they were fixating a target for the very first time. ‘‘Re-clicking'' on previously found targets would indicate that patients erroneously respond to these as new discoveries. Lesions were mapped with high-resolution MRI. Neglect patients with damage involving the right intraparietal sulcus or right inferior frontal lobe ‘‘re-clicked'' on previously found targets on the right at a pathological rate, whereas those with medial occipito-temporal lesions did not. For the intraparietal sulcus patients, the prob- ability of erroneous reclicks on an old target increased with time since first discovering it; whereas for frontal patients it was independent of search time, suggesting different underlying mechanisms in these two types of patient. Re-click deficits correlated with degree of leftward neglect, mainly due to both being severe in intraparietal cases. These results demonstrate that misjudging previously searched locations for new ones can contribute to pathological search in neglect, with potentially different mechanisms being involved in intraparietal versus inferior frontal patients. When combined with a spatial bias to the right, such deficits might explain why many neglect patients often re-examine rightward locations, at the expense of items to their left. |
Tobias Pflugshaupt; Urs P. Mosimann; Roman Von Wartburg; Wolfgang J. Schmitt; Thomas Nyffeler; René M. Müri Hypervigilance-avoidance pattern in spider phobia Journal Article In: Journal of Anxiety Disorders, vol. 19, no. 1, pp. 105–116, 2005. @article{Pflugshaupt2005, Cognitive-motivational theories of phobias propose that patients' behavior is characterized by a hypervigilance-avoidance pattern. This implies that phobics initially direct their attention towards fear-relevant stimuli, followed by avoidance that is thought to prevent objective evaluation and habituation. However, previous experiments with highly anxious individuals confirmed initial hypervigilance and yet failed to show subsequent avoidance. In the present study, we administered a visual task in spider phobics and controls, requiring participants to search for spiders. Analyzing eye movements during visual exploration allowed the examination of spatial as well as temporal aspects of phobic behavior. Confirming the hypervigilance-avoidance hypothesis as a whole, our results showed that, relative to controls, phobics detected spiders faster, fixated closer to spiders during the initial search phase and fixated further from spiders subsequently. |
Thomas Nyffeler; Tobias Pflugshaupt; Helene Hofer; Uli Baas; Klemens Gutbrod; Roman Von Wartburg; Christian W. Hess; René M. Müri Oculomotor behaviour in simultanagnosia: A longitudinal case study Journal Article In: Neuropsychologia, vol. 43, no. 11, pp. 1591–1597, 2005. @article{Nyffeler2005, The aim of the present single case study was to investigate oculomotor recovery in a patient with simultanagnosia due to biparietal hypoxic lesions. Applying visual exploration as well as basic oculomotor tasks in three consecutive test sessions - i.e. 8 weeks, 14 weeks, and 37 weeks after brain damage had occurred - differential recovery was observed. While visual exploration remarkably improved, an impaired disengagement of attention persisted. The improvement of exploration behaviour is interpreted within an oculomotor network theory and implications for a deficit-specific recovery from simultanagnosia are discussed. |
Lisa R. Betts; Christopher P. Taylor; Allison B. Sekuler; Patrick J. Bennett Aging reduces center-surround antagonism in visual motion processing Journal Article In: Neuron, vol. 45, no. 3, pp. 361–366, 2005. @article{Betts2005, Discriminating the direction of motion of a low-contrast pattern becomes easier with increasing stimulus area. However, increasing the size of a high-contrast pattern makes it more difficult for observers to discriminate motion. This surprising result, termed spatial suppression, is thought to be mediated by a form of center-surround suppression found throughout the visual pathway. Here, we examine the counterintuitive hypothesis that aging alters such center-surround interactions in ways that improve performance in some tasks. We found that older observers required briefer stimulus durations than did younger observers to extract information about stimulus direction in conditions using large, high-contrast patterns. We suggest that this age-related improvement in motion discrimination may be linked to reduced GABAergic functioning in the senescent brain, which reduces center-surround suppression in motion-selective neurons. |
Mary Ann Evans; Jean Saint-Aubin What children are looking at during shared storybook reading Journal Article In: Psychological Science, vol. 16, no. 11, pp. 913–920, 2005. @article{Evans2005, Two studies were conducted to determine the extent to which young children fixate on the print of storybooks during shared book reading. Children's books varying in the layout of the print and the richness of the illustrations were displayed on a computer monitor. Each child's mother or preschool teacher read the books while the child sat on the adult's lap wearing an EyeLink headband that recorded visual fixations. In both studies, children spent very little time examining the print regardless of the nature of the print and illustrations. Although fixations on the illustrations were highly correlated with the length of the accompanying text and could be altered by altering the content of the text, fixations to the text were uncorrelated with the length of the text. These results indicate that preschool children engage in minimal exploration of the print during shared book reading. |
Arthur F. Kramer; Jessica C. M. Gonzalez de Sather; Nicholas D. Cassavaugh Development of attentional and oculomotor control Journal Article In: Developmental Psychology, vol. 41, no. 5, pp. 760–772, 2005. @article{Kramer2005, The present study was conducted to examine the development of attentional and oculomotor control. More specifically, the authors were interested in the development of the ability to inhibit an incorrect but prepotent response to a salient distractor. Participants, who ranged in age from 8 to 25 years, performed 3 different eye movement tasks: a prosaccade, an antisaccade, and an oculomotor capture task. The time required to initiate a saccade decreased with age across all 3 tasks. Consistent with previous reports, accuracy was relatively age invariant in the prosaccade task. Performance improved with age, asymptoting at 16 years in the antisaccade task. It is interesting to note that despite the superficial similarity of the antisaccade and oculomotor capture tasks, performance was relatively age invariant in the latter. These results are discussed in terms of developmental differences in the interaction of goal-directed and stimulus-driven processes in the control of attention and action. |
Taina M. Lehtimäki; Ronan G. Reilly Improving eye movement control in young readers Journal Article In: Artificial Intelligence Review, vol. 24, no. 3-4, pp. 477–488, 2005. @article{Lehtimaeki2005, The objective of our study is to design and evaluate an oculomotor reading aid for beginning readers. The aid consists of an eye-tracking device and a computer program that gives real-time feedback in the form of a game to the subject about their fixation position on words. An experimental study was conducted with 8-year-old children. We evaluated the effectiveness of the aid for each child by comparing the landing site distributions before and after playing the game. We found that the peak of the landing site distribution moved towards the optimal viewing position (OVP) for word identification after playing the game. We also determined that training had a positive effect on gaze duration, on the mean and distribution of number of fixations per word, and on the percentage of words with refixations in the majority of subjects. |
Geoffrey Underwood; Nicola Phelps; Chloe Wright; Editha M. Loon; Adam J. Galpin Eye fixation scanpaths of younger and older drivers in a hazard perception task Journal Article In: Ophthalmic and Physiological Optics, vol. 25, no. 4, pp. 346–356, 2005. @article{Underwood2005a, Our previous research has shown that observing patterns of eye fixations is a successful method of establishing differences in underlying cognitive processes between groups of drivers. Eye movements recorded from drivers in a laboratory while they watch film clips recorded from a driver's perspective can be used to identify scanpaths and search patterns that reveal ability differences. In the present study 12 older subjects (60-75 years) and 12 younger subjects (30-45 years) watched clips for potential hazards such as other road users appearing on an intersecting trajectory. Acuity and visual field differences between the two groups were eliminated through screening, so that only age-related differences would emerge. Eye fixations were analysed on a frame-by-frame basis to generate sequences of codes representing the location and object of the viewer's interest, before and during the appearance of a hazard. These codes were analysed for the existence of two fixation scanpaths using Markov Matrices. Unique scanpaths were identified for each group of drivers before and during the hazard. Evidence from the inspection of different objects and from the spread of the search indicated that both groups of driver were sensitive to attentional capture by the appearance of the hazard. Detection of the hazards - both speed and accuracy - was similar for older and younger drivers, although the older drivers perceived the films as being more hazardous in general. There is little evidence in this study of an age-related decline in the search of the scene when detecting hazards. |
2004 |
Frank A. Proudlock; Himanshu Shekhar; Irene Gottlob Age-related changes in head and eye coordination Journal Article In: Neurobiology of Aging, vol. 25, no. 10, pp. 1377–1385, 2004. @article{Proudlock2004, The effect of ageing upon head movements during gaze shifts is unknown. We have investigated age-related changes in head and eye coordination in a group of healthy volunteers. Horizontal head and eye movements were recorded in 53 subjects, aged between 20 and 83 years, during the performance of saccades, antisaccades, smooth pursuit and a reading task. The subjects were divided into three groups, young subjects (20-40 years), middle-aged subjects (41-60 years) and older subjects (over 60 years). Logarithmic transformations of the head gain were significantly greater in the older subjects compared to the young subjects during the saccadic task (P=0.001), antisaccadic task (P=0.0004), smooth pursuit at 20°/s (P=0.001) and 40°/s (P=0.005), but not reading. For saccadic and antisaccadic tasks, the increase in transformed head gain was non-linear with significant differences between older and middle-aged subjects but not middle-aged and young subjects. Head movement tendencies were highly consistent for related tasks. Head movement gain during gaze shifts significantly increases with age, which may contribute to dizziness and balance problems experienced by the elderly. |
Agnieszka Bojko; Arthur F. Kramer; Matthew S. Peterson Age equivalence in switch costs for prosaccade and antisaccade tasks Journal Article In: Psychology and Aging, vol. 19, no. 1, pp. 226–234, 2004. @article{Bojko2004, This study examined age differences in task switching using prosaccade and antisaccade tasks. Significant specific and general switch costs were found for both young and old adults, suggesting the existence of 2 types of processes: those responsible for activation of the currently relevant task set and deactivation of the previously relevant task set and those responsible for maintaining more than 1 task active in working memory. Contrary to the findings of previous research, which used manual response tasks with arbitrary stimulus-response mappings to study task-switching performance, no age-related deficits in either type of switch costs were found. These data suggest age-related sparing of task-switching processes in situations in which memory load is low and stimulus-response mappings are well learned. |
Urs P. Mosimann; J. Felblinger; P. Ballinari; Christian W. Hess; René M. Müri Visual exploration behaviour during clock reading in Alzheimer's disease Journal Article In: Brain, vol. 127, no. 2, pp. 431–438, 2004. @article{Mosimann2004, Eye movement behaviour during visual exploration of 24 patients with probable Alzheimer's disease and 24 age-matched controls was compared in a clock reading task. Controls were found to focus exploration on distinct areas at the end of each clock hand. The sum of these two areas of highest fixation density was defined as the informative region of interest (ROI). In Alzheimer's disease patients, visual exploration was less focused, with fewer fixations inside the ROI, and the time until the first fixation was inside the ROI was significantly delayed. Changes of fixation distribution correlated significantly with the ability to read the clock correctly, but did not correlate with dementia severity. In Alzheimer's disease patients, fixations were longer and saccade amplitudes were smaller. The altered visual exploration in Alzheimer's disease might be related to parietal dysfunction or to an imbalance between a degraded occipito-parietal and relatively preserved occipito-temporal visual network. |
Nicholas Cassavaugh; Arthur F. Kramer; Matthew S. Peterson Aging and the strategic control of the fixation offset effect Journal Article In: Psychology and Aging, vol. 19, no. 2, pp. 357–361, 2004. @article{Cassavaugh2004, A study was conducted to examine potential age-related differences in the strategic control of exogenous and endogenous saccades within the context of the fixation offset effect (FOE; i.e., faster saccades when a fixation point is removed than when it is left on throughout a trial). Subjects were instructed to make rapid saccades either on the basis of a suddenly appearing peripheral visual stimulus (exogenous saccade) or in response to a tone (endogenous saccade). On half of the trials the fixation point was removed simultaneously with the occurrence of the cue stimulus. Subjects' preparatory set was varied by manipulating the proportion of saccades generated to a visual and auditory stimulus within a trial block. Young and old adults both produced FOEs, and the FOEs were strategically modulated by preparatory set. The data are discussed in terms of aging and oculomotor control. |
Paresh Malhotra; Sabira K. Mannan; Jon Driver; Masud Husain Special section impaired spatial working memory: One component of the visual neglect syndrome ? Journal Article In: Cortex, vol. 40, no. 4-5, pp. 667–676, 2004. @article{Malhotra2004, Both impaired spatial working memory (SWM) and unilateral neglect may follow damage to the right parietal lobe. We propose that impaired SWM can exacerbate visual neglect, due to failures in remembering locations that have already been searched. When combined with an attentional bias to the ipsilesional right side, such a SWM impairment should induce recursive search of ipsilesional locations. Here we studied a left neglect patient with a right temporoparietal haemorrhage. On a nonlateralised, purely vertical SWM task, he was impaired in retaining spatial locations. In a visual search task, his eye position was monitored while his spatial memory was probed. He recursively searched through right stimuli, re-fixating previously inspected items, and critically treated them as if they were new discoveries, consistent with the SWM deficit. When his recovery was tracked over several months, his SWM deficit and left neglect showed concurrent improvements. We argue that impaired SWM may be one important component of the visual neglect syndrome. |
Tobias Pflugshaupt; Stefanie Almoslöchner Bopp; Dörthe Heinemann; Urs P. Mosimann; Roman Von Wartburg; Thomas Nyffeler; Christian W. Hess; René M. Müri Residual oculomotor and exploratory deficits in patients with recovered hemineglect Journal Article In: Neuropsychologia, vol. 42, no. 9, pp. 1203–1211, 2004. @article{Pflugshaupt2004, Several studies on hemineglect have reported that patients recover remarkably well when assessed with neuropsychological screening tests, however, they show deficits on novel or complex tasks. We investigated whether such deficits can be revealed with eye movement analysis, applying two basic oculomotor tasks as well as two exploratory tasks. Eye movements were recorded in eight hemineglect patients at least eleven months after right-hemisphere brain damage had occurred. Sixteen healthy volunteers participated in the control group. Regarding the basic oculomotor tasks, only the overlap task revealed residual deficits in patients, suggesting that a directional deficit in disengaging attention persisted during recovery. Further residual deficits were evident in the exploratory tasks. When everyday scenes were explored, patients showed a bias in early orienting towards the ipsilateral hemispace. In a search task, they demonstrated the same orienting bias as well as a non-directional deficit concerning search times. Moreover, patients preferentially fixated in the contralateral hemispace, but did not benefit from this asymmetry in terms of search times, i.e. they did not detect contralateral targets faster than ipsilateral ones. This suggests a dissociation between oculomotor processes and attentional ones. In conclusion, we have identified behavioural aspects that seem to recover slower than others. A disengagement deficit and biases in early orienting have been the most pronounced residual oculomotor deficits. |
Christoph Helmchen; Andreas Sprenger; Holger Rambold; Thurid Sander; D. Kompf; D. Straumann Effect of 3,4-diaminopyridine on the gravity dependence of ocular drift in downbeat nystagmus Journal Article In: Neurology, vol. 63, no. 4, pp. 752, 2004. @article{Helmchen2004, The pathomechanism of downbeat nystagmus (DBN) remains controversial but each mechanism has to account for 1) its gaze-evoked vertical centripetal component which increases on down and lateral gaze,¹ and 2) the vertical bias component of the upward slow phase velocity (SPV) in gaze straight ahead. The vertical velocity bias of DBN has a gravity-dependent component which leads to maximal drift velocity when patients lie in prone position and minimal in supine position.² Recently, 3,4- diaminopyridine (3,4-DAP)³ has been shown to be effective in reducing DBN in patients with their heads upright. However, DBN of several of those patients showed only small changes. One reason might be that gravity-dependent mechanisms were not considered. |
Millard Reschke; Jeffrey T. Somers; R. John Leigh; Jody M. Krnavek; Ludmila Kornilova; Inessa Kozlovskaya; Jacob J. Bloomberg; William H. Paloski Sensorimotor recovery following spaceflight may be due to frequent square-wave saccadic intrusions Journal Article In: Aviation Space and Environmental Medicine, vol. 75, no. 8, pp. 700–704, 2004. @article{Reschke2004, Square-wave jerks (SWJs) are small, involuntary saccades that disrupt steady fixation. We report the case of an astronaut (approximately 140 d on orbit) who showed frequent SWJs, especially postflight, but who showed no impairment of vision or decrement of postflight performance. These data support the view that SWJs do not impair vision because they are paired movements, consisting of a small saccade away from the fixation position followed, within 200 ms, by a corrective saccade that brings the eye back on target. Since many returning astronauts show a decrement of dynamic visual function during postflight locomotion, it seems possible that frequent SWJs improved this astronaut's visual function by providing postsaccadic enhancement of visual fixation, which aided postflight performance. Certainly, frequent SWJs did not impair performance in this astronaut, who had no other neurological disorder. |
Michael D. Crossland; Louise E. Culham; Gary S. Rubin Fixation stability and reading speed in patients with newly developed macular disease. Journal Article In: Ophthalmic and Physiological Optics, vol. 24, pp. 327–333, 2004. @article{Crossland2004a, Background: Patients with macular disease and central scotomas must use a peripheral, preferred retinal locus (PRL) in place of their damaged fovea. This paper investigates the development of the PRL, with particular reference to the stability of fixation. Methods: Twenty-five patients with age-related and juvenile macular disease were recruited. All patients had developed a scotoma in their better eye within the previous 2 weeks. Patients were assessed using a scanning laser ophthalmoscope and an infra-red gazetracker on four further occasions over the next 12 months. Results: A linear relationship exists between reading speed and fixation stability for patients and control subjects. Fixation stability was not related to scotoma size, visual acuity or contrast sensitivity. Changes in fixation stability account for 54% of the variance in change in reading speed over the course of this study. Conclusions: The deficit in reading speed in patients with macular disease can be partially attributed to impairments in fixation stability. |
Michael D. Crossland; M. Sims; R. F. Galbraith; Gary S. Rubin Evaluation of a new quantitative technique to assess the number and extent of preferred retinal loci in macular disease Journal Article In: Vision Research, vol. 44, no. 13, pp. 1537–1546, 2004. @article{Crossland2004, Patients with scotomas due to macular disease may use more than one preferred retinal locus (PRL) for fixation. We have developed and evaluated an objective, quantitative technique to determine the number of PRLs used during an episode of fixation and the extent of each locus. In five of eight adults with macular disease our techniques consistently indicated the presence of multiple PRLs. Patients with multiple PRLs were more likely to have suffered recent vision loss in the tested eye. Our technique describes fixation more fully than the traditional method of calculating a single bivariate contour ellipse area. |
Caren Bellmann; Mary P. Feely; Michael D. Crossland; Stamatina A. Kabanarou; Gary S. Rubin Fixation stability using central and pericentral fixation targets in patients with age-related macular degeneration Journal Article In: Ophthalmology, vol. 111, no. 12, pp. 2265–2270, 2004. @article{Bellmann2004, To determine fixation stability for central and pericentral fixation targets in patients with age-related macular degeneration (AMD). Comparative study. Twelve patients having late-stage AMD involving the fovea and 10 age-matched controls having no other eye diseases and visual acuity better than 20/25. Six different fixation targets (1°cross; 1°filled circle; 1°letter x; small 4-point diamond; large 4-point diamond using dimensions as in a field analyzer; large-crossover whole-image diagonal with open 1°center) were presented on a high-resolution monitor. Before examination, subjects were given verbal instructions to move their eye to see the center of the target best. Fixation stability was measured for the preferred eye, with the fellow eye occluded, using a gaze tracker. Fixation stability was quantified by calculating the bivariate contour ellipse area (BCEA) over 30 seconds for each target. For statistical analysis, BCEA values (minutes of arc2) were converted into their logarithms. The absolute retinal scotoma for the study eye was determined using a scanning laser ophthalmoscope. Bivariate contour ellipse area. Visual acuity in patients (age range, 57-87 years) ranged from 20/32 to 20/600. The lowest BCEA values were found for the 1°letter x in patients (mean, 12052.2%±254.0%) and for the 1°cross in normal subjects (mean, 1286.9%±47.8%); the highest BCEA values were found for the small 4-point diamond in patients (mean, 23109.5%±298.3%) and for the large 4-point diamond in normals (age range, 62-79 years) (mean, 3229.2%±105.4%). The difference between the targets was significant for normal subjects (analysis of variance [ANOVA], P<0.01) but not for patients (ANOVA, P>0.05). In normals, BCEA values were significantly lower for central fixation targets than for pericentral fixation targets (P<0.01). Fixation is significantly less stable for pericentral fixation targets in normal subjects, indicating an advantage for central fixation targets. These results are particularly significant for any clinical and experimental testing method that requires the patient to maintain stable fixation. |
T. M. Blekher; Robert D. Yee; S. C. Kirkwood; A. M. Hake; J. C. Stout; Marjorie R. Weaver; Tatiana M. Foroud Oculomotor control in asymptomatic and recently diagnosed individuals with the genetic marker for Huntington's disease Journal Article In: Vision Research, vol. 44, no. 23, pp. 2729–2736, 2004. @article{Blekher2004, We compared oculomotor control among individuals in the early stages of Huntington’s disease (HD), with that of individuals who are presymptomatic HD gene carriers (PSGC) and nongene carriers (NGC). The oculomotor testing paradigm included both traditional tests and a novel experimental procedure to assess visual scanning. Traditional tests elicited saccades, pursuit and optokinetic nystagmus (OKN). HD patients demonstrated marked delay in the initiation of volitional saccades (anti-saccade and memory-guided saccades), a reduced number of correct volitional saccades, reduced velocity of saccades, and a decreased OKN gain. We also studied visual scanning while the participants completed the Digit Symbol Subscale of the Wechsler Adult Intelligence Survey-Revised (WAIS-R). The HD participants demonstrated an abnormal gaze strategy, which may be associated with attention and/or planning deficits.Differences between the PSGC and NGC groups were only observed for two measures: PSGC had a decreased number of memory-guided saccades and a subtle delay in the initiation of volitional saccades. Our results suggest that oculomotor measures are a sensitive biomarker in the early stage of HD and demonstrate that the combination of more traditional oculomotor tests with visual scanning tests is useful in the evaluation of visual performance. © 2004 Elsevier Ltd. All rights reserved. |
Josef N. Geest; Gerardina C. Lagers-van Haselen; J. M. Hagen; L. C. P. Govaerts; I. F. M. Coo; Chris I. De Zeeuw; Maarten A. Frens Saccade dysmetria in Williams-Beuren syndrome Journal Article In: Neuropsychologia, vol. 42, no. 5, pp. 569–576, 2004. @article{Geest2004, Numerous studies have described the poor visuo-spatial processing capacities of subjects with Williams-Beuren syndrome (WBS), a genetically based developmental disorder. Since visual perception and eye movements are closely related we hypothesized that the poor visuo-spatial processing capacities of subjects with WBS might be related to a poor saccadic control. Thereto, we recorded horizontal and vertical saccadic eye movements to targets using infrared video-oculography in 27 subjects with WBS and eight healthy controls. In the WBS group saccadic gains were highly variable, both between and within individual subjects, and they often needed more than one correction saccade to reach the target. Ten (out of a subgroup of 22) WBS subjects showed a large number of hypometric and/or hypermetric saccades, and, also a left-right asymmetry in saccadic gains was observed in WBS. We conclude that the observed impairments in saccadic control are likely to affect the proper processing of visuo-spatial information. |
2003 |
N. J. Upton; Timothy L. Hodgson; G. T. Plant; Richard J. S. Wise; Alexander P. Leff "Bottom-up" and "top-down" effects on reading saccades: A case study Journal Article In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 74, no. 10, pp. 1423–1428, 2003. @article{Upton2003, OBJECTIVE: To investigate the role right foveal/parafoveal sparing plays in reading single words, word arrays, and eye movement patterns in a single case with an incongruous hemianopia. METHODS: The patient, a 48-year-old right handed male with a macular sparing hemianopia in his left eye and a macular splitting hemianopia in his right eye, performed various reading tasks. Single word reading speeds were monitored using a "voice-trigger" system. Eye movements were recorded while reading three passages of text, and PET data were gathered while the subject performed a variety of reading tasks in the camera. RESULTS: The patient was faster at reading single words and text with his left eye compared with his right. A small word length effect was present in his right eye but not his left. His eye movement patterns were more orderly when reading text with his left eye, making fewer saccades. The PET data provided evidence of "top-down" processes involved in reading. Binocular single word reading produced activity in the representation of foveal V1 bilaterally; however, text reading with the left eye only was associated with activation in left but not right parafoveal V1, despite there being visual stimuli in both visual fields. CONCLUSIONS: The presence of a word length effect (typically associated with pure alexia) can be caused by a macular splitting hemianopia. Right parafoveal vision is not critically involved in single word identification, but is when planning left to right reading saccades. The influence of top-down attentional processes during text reading can be visualised in parafoveal V1 using PET. |
Monika Harvey; Iain D. Gilchrist; Bettina Olk; Keith Muir Eye-movement patterns do not mediate size distortion effects in hemispatial neglect: Looking without seeing Journal Article In: Neuropsychologia, vol. 41, no. 8, pp. 1114–1121, 2003. @article{Harvey2003, Over the last decade a range of studies have shown that some patients with hemispatial neglect subjectively underestimate the size of objects presented in their contralesional hemispace. Recently, it has been suggested that the effect is simply due to either hemianopia [Brain 124 (2001) 527], or the combination of neglect and hemianopia [Neurology 52 (1999) 1845]. In the current study we asked right hemisphere lesioned patients with and without neglect and hemianopia as well as healthy controls to judge either two horizontal or vertical lines presented simultaneously in right and left hemispace and monitored their eye movements. Three out of the six patients showed the predicted size distortion effect for horizontal lines. We found no evidence that the effect was mediated by eye movements. The two neglect patients who showed the strongest left side underestimation showed symmetrical (left, right) scanning of the lines both in terms of number of fixations and fixation time, yet they still failed to judge the relative size veridically. In addition, we did not find strong evidence for a link with hemianopia. We therefore propose that the effect reflects a computational/representational failure of processing for horizontal extent. |
Masud Husain; Andrew Parton; Timothy L. Hodgson; Dominic J. Mort; Geraint Rees Self-control during response conflict by human supplementary eye field Journal Article In: Nature Neuroscience, vol. 6, no. 2, pp. 117–118, 2003. @article{Husain2003, Although medial frontal cortex is considered to have an important role in planning behavior and monitoring errors, the specific contributions of regions within it are poorly understood1, 2, 3. Here we report that a patient with a highly selective lesion of a medial frontal motor area—the supplementary eye field (SEF)—lacked control in changing the direction of his eye movement from either a previous intention or behavioral 'set'; however, he monitored his errors well and corrected them quickly. The results indicate a key new role for the SEF and show that medial frontal mechanisms for self-control of action may be highly specific, with the SEF critically involved in implementing oculomotor control during response conflict, but not in error monitoring. |
Caroline J. Ketcham; Timothy L. Hodgson; Christopher Kennard; George E. Stelmach Memory-motor transformations are impaired in Parkinson s disease Journal Article In: Experimental Brain Research, vol. 149, pp. 30–39, 2003. @article{Ketcham2003, Parkinson's disease patients are known to suffer loss of dopaminergic input to the rostral caudate nucleus. Recent functional magnetic resonance imaging (fMRI) studies have implicated this structure in the transformation of spatial information in memory to guide action, suggesting that memory to motor transformations may be selectively impaired in Parkinson's disease. In order to investigate this possibility we tested a group of Parkinson's disease patients (PDs) using a memory- guided pointing task. Of interest was whether patients showed reduced accuracy in the task as a function of memory load. Twelve PD patients and 13 elderly controls were asked to recall single or four step target sequences with 2 time delays (500 and 3,500 ms). In all memory- guided conditions PD patients showed increased variabil- ity in memory-guided movement end-points. This effect was not affected by delay, number of items, or the sequence familiarity. The results are consistent with increased variability in memory-motor transformations in early PD, due to dopamine depletion within the rostral caudate nucleus. |
Elliot M. Frohman; Padraig O'Suilleabhain; Richard B. Dewey; Teresa C. Frohman; Phillip D. Kramer A new measure of dysconjugacy in INO: The first-pass amplitude Journal Article In: Journal of the Neurological Sciences, vol. 210, no. 1-2, pp. 65–71, 2003. @article{Frohman2003, Background: The ratios of abducting to adducting eye movements (versional dysconjugacy index, VDI) for saccadic velocity and acceleration have been useful measures by which to objectively characterize internuclear ophthalmoparesis (INO). Amplitude measures of dysconjugacy have been less useful, given that many patients maintain the ability to ultimately reach a centrifugal fixation target and that traditional amplitude measures of VDI have focused on this 'final amplitude' (FA) position. Methods: We utilized infrared oculography to define a new amplitude measure of dysconjugacy in 42 multiple sclerosis (MS) patients with INO. The first-pass amplitude (FPA)-VDI is the ratio of abduction/adduction eye movement amplitudes computed at the time when the abducting eye initially achieves the centrifugal horizontal fixation target. Results: FPA-VDI values were significantly more sensitive and specific than FA-VDI values in demonstrating dysconjugacy in INO, and there was a 14-fold increase in dysconjugacy as measured by FPA-VDI Z-scores when compared to FA-VDI Z-scores. Conclusion: Consideration of velocity (pulse) and amplitude (step) components of dysconjugacy in patients with INO can provide a greater understanding of the dynamic aspects of this syndrome. We propose to characterize the relationship between the pathophysiology of INO and neuroradiologic measures of tissue injury in MS. |
Teresa C. Frohman; Elliot M. Frohman; Padraig O'Suilleabhain; A. R. Salter; Richard B. Dewey; N. Hogan; S. Galetta; A. G. Lee; D. Straumann; J. Noseworthy; D. Zee; J. Corbett; J. Corboy; V. M. Rivera; Phillip D. Kramer Accuracy of clinical detection of INO in MS: Corroboration with quantitative infrared oculography Journal Article In: Neurology, vol. 61, no. 6, pp. 848–850, 2003. @article{Frohman2003a, The authors compared the accuracy of clinical detection (by 279 physician observers) of internuclear ophthalmoparesis (INO) with that of quantitative infrared oculography. For the patients with mild adduction slowing, INO was not identified by 71%. Intermediate dysconjugacy was not detected by 25% of the evaluators. In the most severe cases, INO was not identified by only 6%. Oculographic techniques significantly enhance the precision of INO detection compared to the clinical exam. |
Michael Coesmans; Peter A. Sillevis Smitt; David J. Linden; Ryuichi Shigemoto; Tomoo Hirano; Yoshinori Yamakawa; Adriaan M. Alphen; Chongde Luo; Josef N. Geest; Johan M. Kros; Carlos A. Gaillard; Maarten A. Frens; Chris I. De Zeeuw Mechanisms underlying cerebellar motor deficits due to mGluR1-autoantibodies Journal Article In: Annals of Neurology, vol. 53, no. 3, pp. 325–336, 2003. @article{Coesmans2003, Patients with Hodgkin's disease can develop paraneoplastic cerebellar ataxia because of the generation of autoantibodies against mGluR1 (mGluR1-Abs). Yet, the pathophysiological mechanisms underlying their motor coordination deficits remain to be elucidated. Here, we show that application of IgG purified from the patients' serum to cerebellar slices of mice acutely reduces the basal activity of Purkinje cells, whereas application to the flocculus of mice in vivo evokes acute disturbances in the performance of their compensatory eye movements. In addition, the mGluR1-Abs block induction of long-term depression in cultured mouse Purkinje cells, whereas the cerebellar motor learning behavior of the patients is affected in that they show impaired adaptation of their saccadic eye movements. Finally, postmortem analysis of the cerebellum of a paraneoplastic cerebellar ataxia patient showed that the number of Purkinje cells was significantly reduced by approximately two thirds compared with three controls. We conclude that autoantibodies against mGluR1 can cause cerebellar motor coordination deficits caused by a combination of rapid effects on both acute and plastic responses of Purkinje cells and chronic degenerative effects. |
Hendrik Chris Dijkerman; Robert D. McIntosh; David Milner; Yves Rossetti; Caroline Tilikete; Richard C. Roberts Ocular scanning and perceptual size distortion in hemispatial neglect: Effects of prism adaptation and sequential stimulus presentation Journal Article In: Experimental Brain Research, vol. 153, no. 2, pp. 220–230, 2003. @article{Dijkerman2003, When asked to compare two lateralized shapes for horizontal size, neglect patients often indicate the left stimulus to be smaller. Gainotti and Tiacci (1971) hypothesized that this phenomenon might be related to a rightward bias in the patients' gaze. This study aimed to assess the relation between this size underestimation and oculomotor asymmetries. Eye movements were recorded while three neglect patients judged the horizontal extent of two rectangles. Two experimental manipulations were performed to increase the likelihood of symmetrical scanning of the stimulus display. The first manipulation entailed a sequential, rather than simultaneous presentation of the two rectangles. The second required adaptation to rightward displacing prisms, which is known to reduce many manifestations of neglect. All patients consistently underestimated the left rectangle, but the pattern of verbal responses and eye movements suggested different underlying causes. These include a distortion of space perception without ocular asymmetry, a failure to view the full leftward extent of the left stimulus, and a high-level response bias. Sequential presentation of the rectangles and prism adaptation reduced ocular asymmetries without affecting size underestimation. Overall, the results suggest that leftward size underestimation in neglect can arise for a number of different reasons. Incomplete leftward scanning may perhaps be sufficient to induce perceptual size distortion, but it is not a necessary prerequisite. |
Nicholas D. Cassavaugh; Arthur F. Kramer; David E. Irwin Influence of task-irrelevant onset distractors on the visual search performance of young and old adults Journal Article In: Aging, Neuropsychology, and Cognition, vol. 10, no. 1, pp. 44–60, 2003. @article{Cassavaugh2003, We examined potential age-related differences in attentional and oculomotor capture by single and multiple abrupt onsets in a singleton search paradigm. 24 participants were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. Either single or dual onset task-irrelevant distractors were presented simultaneously with the color change that defined the target, or one onset distractor was presented prior to and another onset distractor was presented during the participant's initial eye movement away from fixation. Young and old adults misdirected their eyes to the single and dual onset task-irrelevant distractors, on an equivalent proportion of trials, relative to control trials. However, older adults' saccade latencies and RTs were influenced to a greater extent by onsets compared to younger adults'. These data are discussed in terms of age-related differences in attentional control and oculomotor capture. |
Angela M. Colcombe; Arthur F. Kramer; David E. Irwin; Matthew S. Peterson; Stanley Colcombe; Sowon Hahn Age-related effects of attentional and oculomotor capture by onsets and color singletons as a function of experience Journal Article In: Acta Psychologica, vol. 113, no. 2, pp. 205–225, 2003. @article{Colcombe2003, The present experiment examined the degree to which experience with different stimulus characteristics affects attentional capture, particularly as related to aging. Participants were presented with onset target/color singleton distractor or color singleton target/onset distractor pairs across three experimental sessions. The target/distractor pairs were reversed in the second session such that the target in the first session became the distractor in the second and third sessions. For both young and old adults previous experience with color as a target defining feature influenced oculomotor capture with task-irrelevant color distractors. Experience with sudden onsets had the same effect for younger and older adults, although capture effects were substantially larger for onset than for color distractors. Experience-based capture effects diminished relatively rapidly after target and distractor-defining properties were reversed. The results are discussed in terms of top-down and stimulus-driven effects on age-related differences in attentional control. ©2003 Elsevier Science B.V. All rights reserved. |
Willem P. A. Kelders; Gert Jan Kleinrensink; Josef N. Geest; Louw Feenstra; Chris I. De Zeeuw; Maarten A. Frens Compensatory increase of the cervico-ocular reflex with age in healthy humans Journal Article In: Journal of Physiology, vol. 553, no. 1, pp. 311–317, 2003. @article{Kelders2003, The cervico-ocular reflex (COR) is an ocular stabilization reflex that is elicited by rotation of the neck. It works in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) in order to prevent visual slip over the retina due to self-motion. The gains of the VOR and OKR are known to decrease with age. We have investigated whether the COR, a reflexive eye movement elicited by rotation of the neck, shows a compensatory increase and whether a synergy exists between the COR and the other ocular stabilization reflexes. In the present study 35 healthy subjects of varying age (20-86 years) were rotated in the dark in a trunk-to-head manner (the head fixed in spaced with the body passively rotated under it) at peak velocities between 2.1 and 12.6 deg s-1 as a COR stimulus. Another 15 were subjected to COR, VOR and OKR stimuli at frequencies between 0.04 and 0.1 Hz. Three subjects participated in both tests. The position of the eyes was recorded with an infrared recording technique. We found that the COR-gain increases with increasing age and that there is a significant covariation between the gains of the VOR and COR, meaning that when VOR increases, COR decreases and vice versa. A nearly constant phase lag between the COR and the VOR of about 25 deg existed at all stimulus frequencies. |
I. T. Armstrong; Douglas P. Munoz Inhibitory control of eye movements during oculomotor countermanding in adults with attention-deficit hyperactivity disorder Journal Article In: Experimental Brain Research, vol. 152, no. 4, pp. 444–452, 2003. @article{Armstrong2003a, Children with attention-deficit hyperactivity disorder (ADHD) are impulsive, and that impulsiveness can be measured using a countermanding task. Although the overt behaviors of ADHD attenuate with age, it is not clear how well impulsiveness is controlled in adults with ADHD. We tested ADHD adults with an oculomotor countermanding task. The task included two conditions: on 75% of the trials, participants viewed a central fixation marker and then looked to an eccentric target that appeared simultaneous with the disappearance of the fixation marker; on 25% of the trials, a signal was presented at variable delays after target appearance. The signal instructed subjects to stop, or countermand, an eye movement to the target. A correct movement in this case would be to hold gaze at the central fixation location. We expected ADHD participants to be impulsive in their countermanding performance. Additionally, we expected that a visual stop signal at the central fixation location would assist oculomotor countermanding because the signal is presented in the "stop" location, at fixation. To test whether a central stop signal positively biased countermanding, we used a three types of stop signal to instruct the stop: a central visual marker, a peripheral visual signal, and a non-localized sound. All subjects performed best with the central visual stop signal. Subjects with ADHD were less able to countermand eye movements and were influenced more negatively by the non-central signals. Oculomotor countermanding may be useful for quantifying impulsive dysfunction in adults with ADHD especially if a non-central stop signal is applied. |
I. T. Armstrong; Douglas P. Munoz Attentional blink in adults with attention-deficit hyperactivity disorder: Influence of eye movements Journal Article In: Experimental Brain Research, vol. 152, no. 2, pp. 243–250, 2003. @article{Armstrong2003, The attentional blink paradigm tests attention by overloading it: a list of stimuli is presented very rapidly one after another at the same location on a computer screen, each item overwriting the last, and participants monitor the list using two criteria [e.g. detect the target (red letter) and identify the probe (letter p)]. If the interval between the target and the probe is greater than about 500 ms, both are usually reported correctly, but, when the interval between the target and the probe is within 200-500 ms, report of the probe declines. This decline is the attentional blink, an interval of time when attention is supposedly switching from the first criterion to the second. The attentional blink paradigm should be difficult to perform correctly without vigilantly attending to the rapidly presented list. Vigilance tasks are often used to assess attention-deficit hyperactivity disorder (ADHD). Symptoms of the disorder include hyperactivity and attentional dysfunction; however, some people with ADHD also have difficulty maintaining gaze at a fixed location. We tested 15 adults with ADHD and their age- and sex-matched controls, measuring accuracy and gaze stability during the attentional blink task. ADHD participants reported fewer targets and probes, took longer to recover from the attentional blink, made more eye movements, and made identification errors consistent with non-perception of the letter list. In contrast, errors made by control participants were consistent with guessing (i.e., report of a letter immediately preceding or succeeding the correct letter). Excessive eye movements result in poorer performance for all participants; however, error patterns confirm that the weak performance of ADHD participants may be related to gaze instability as well as to attentional dysfunction. |
Chiang-Shan Ray Li; Hsueh-Ling Chang; Shih Chieh Lin Inhibition of return in children with attention deficit hyperactivity disorder Journal Article In: Experimental Brain Research, vol. 149, no. 1, pp. 125–130, 2003. @article{Li2003, Earlier studies have suggested an impairment in the attention and eye movement control of children with ADHD. An important phenomenon in the control of attentional shifts and eye movements is the inhibition of return (IOR), which states that our brain works in a way that prevents our attention from returning to a spatial location that has been attended to, either overtly or covertly. This current study addresses whether the IOR in oculomotor planning is compromised in children with ADHD. Eleven ADHD and 12 age- and gender-matched control subjects participated in a behavioral task, in which they made saccades to a peripheral target after a valid, invalid or neutral cue. The latency difference between cued and uncued saccades over a range of cue-target onset asynchrony as well as the positive component of this latency profile (i.e., IOR) was compared between groups. The results show that ADHD children demonstrate a biphasic latency profile that is grossly similar to that observed in control subjects, although the magnitude of IOR appears to be slightly smaller in ADHD subjects. These preliminary results suggest that the inhibitory attention mechanism subserving IOR is at least not fully compromised in ADHD children. |
2002 |
Bettina Olk; Monika Harvey; Iain D. Gilchrist First saccades reveal biases in recovered neglect Journal Article In: Neurocase, vol. 8, no. 4, pp. 306–313, 2002. @article{Olk2002, Hemispatial neglect affects the ability to explore space on the side opposite a brain lesion. This deficit is also mirrored in abnormal saccadic eye movement patterns. The present study investigated if the recovery of neglect is also reflected in saccadic eye movements. Patient AF, who displayed strong hemispatial neglect 1 month post-right thalamic stroke, had largely recovered 3 months later when tested on visual exploration tasks of the Behavioural Inattention Test. At this stage, AF was tested on a visual search task while his eye movements (direction, latencies and amplitudes of first saccades) and manual reaction times were recorded. The experimental conditions differed with respect to stimulus number and distracter type and increased in difficulty. AF correctly generated saccades into the neglected field when the target was presented alone. In contrast, a considerable left/right difference was present for all multiple-stimulus search displays. Although recovered from neglect in standardized assessment, AF showed a strong rightward bias resulting in highly asymmetric response times and eye movement behaviour. We conclude that eye movement patterns are far more susceptible to remaining spatial impairments and can thus provide a sensitive means to assess the extent of neglect recovery. |
Tanja R. M. Coeckelbergh; Frans W. Cornelissen; Wiebo H. Brouwer; Aart C. Kooijman The effect of visual field defects on eye movements and practical fitness to drive Journal Article In: Vision Research, vol. 42, no. 5, pp. 669–677, 2002. @article{Coeckelbergh2002, Eye movements of subjects with visual field defects due to ocular pathology were monitored while performing a dot counting task and a visual search task. Subjects with peripheral field defects required more fixations, longer search times, made more errors, and had shorter fixation durations than control subjects. Subjects with central field defects performed less well than control subjects although no specific impairment could be pinpointed. In both groups a monotonous relationship was observed between the visual field impairment and eye movement parameters. The use of eye movement parameters to predict viewing behavior in a complex task (e.g. driving) was limited. |
Charles A. Collin; Avi Chaudhuri Using MATLAB with the Psychophysics Toolbox to present the heterochromatic fusion nystagmus stimulus Journal Article In: Behavior Research Methods, Instruments & Computers, vol. 34, no. 4, pp. 500–508, 2002. @article{Collin2002, We present a program for MATLAB that generates and presents the heterochromatic fusion nystagmus stimulus. This stimulus allows assessment of isoluminant states through recordings of reflexive eye movements (optokinetic nystagmus). The reflexive nature of the subject's response makes this stimulus especially useful with nonverbal subjects, such as children and animals. Unfortunately, the stimulus is complex and difficult to program. By presenting the present program, we hope to help those who wish to use this tool in their research. The code of the function can be downloaded at www. dal.ca/-mcmullen/downloads.html. |
Michael D. Crossland; Gary S. Rubin The use of an infrared eyetracker to measure fixation stability Journal Article In: Optometry and Vision Science, vol. 79, no. 11, pp. 735–739, 2002. @article{Crossland2002, PURPOSE: To assess fixation stability in patients, a scanning laser ophthalmoscope (SLO) has typically been required. Disadvantages of this technique include the need for a fixed viewing distance and rigid head support. Some modern infrared eyetrackers do not have these constraints. The purpose of this study was to compare fixation stability measurements made with these instruments. METHODS: Normal subjects were asked to fixate a 2.5 degrees high cross while fixation was measured with a SLO and an infrared eyetracker. Bivariate contour ellipse areas were calculated. RESULTS: There was a linear relationship between the bivariate contour ellipse areas measured using each instrument. Bivariate contour ellipse areas returned from the eyetracker were larger. There was no difference in test-retest variability between the instruments. CONCLUSIONS: The eyetracker indicates fixation to be less stable than the SLO does, perhaps because of eye movements to compensate for small head movements. Our eyetracker can be used to analyze fixation when viewing images at any distance, without the need for head immobilization. The eyetracker and the SLO complement each other in the investigation of visual behavior. |
M. L. M. Tant; Frans W. Cornelissen; Aart C. Kooijman; Wiebo H. Brouwer Hemianopic visual field defects elicit hemianopic scanning Journal Article In: Vision Research, vol. 42, no. 10, pp. 1339–1348, 2002. @article{Tant2002, Previous explanations for the variability in success of compensating for homonymous hemianopia (HH) has been in terms of extent of the brain injury. In using on-line eye movement registrations, we simulated HH in 16 healthy subjects and compared their scanning performance on a dot counting task to their own "normal" condition and to real HH patients' performance. We evidenced clear parallels between simulated and real HH, suggesting that hemianopic scanning behaviour is primarily visually elicited, namely by the visual field defect, and not by the additional brain damage. We further observed age-related processes in compensating for the HH. |
Frank A. Proudlock; Irene Gottlob; Cris S. Constantinescu Oscillopsia without nystagmus caused by head titubation in a patient with multiple sclerosis Journal Article In: Journal of Neuro-Ophthalmology, vol. 22, no. 2, pp. 88–91, 2002. @article{Proudlock2002, Oscillopsia in patients who have brain stem disorders but not nystagmus is attributed to a failure of the vestibular-ocular reflex (VOR) to compensate for head movements. We report a patient who had marked head titubation and oscillopsia in aggressive multiple sclerosis but no nystagmus. Her severe head titubation precluded our ability to measure a VOR accurately. Because oscillopsia has also been described after rapid voluntary head oscillations in normal subjects, we queried whether the oscillopsia in our patient could be ascribed to the head movement alone. Six normal control subjects did not experience oscillopsia while shaking their heads at the same frequency as the patient's titubation. We conclude that the oscillopsia in our patient was probably the result of an impaired VOR or an alternative compensatory mechanism. |
Monika Harvey; Bettina Olk; Keith Muir; Iain D. Gilchrist Manual responses and saccades in chronic and recovered hemispatial neglect: A study using visual search Journal Article In: Neuropsychologia, vol. 40, no. 7, pp. 705–717, 2002. @article{Harvey2002, Hemispatial neglect affects both the ability to respond to targets on the contralesional side of space and to programme saccades to such targets. In the current study, we looked in detail at saccade programming and manual reaction times (RTs) in a range of visual search tasks, in which task difficulty was systematically increased by changing the nature of the distractors. In condition 1, the target was presented with no distractors. In the other conditions, displays contained three distractors that were changed across conditions to manipulate similarity to the target and so task difficulty. We tested two neglect patients, one chronic, one recovered along with two RCVA control patients and 12 age-matched controls. Both neglect patients studied could successfully execute saccades into the neglected field when the target was presented alone. However, a dissociation emerged between the two patients when the target was presented with distractor items. Patient ERs first saccade to target performance in the three search conditions revealed clear effects of distractor type. In contrast for the recovered patient AF, the left/right difference was present for all search displays and appeared to be constant regardless of distractor type. This differential pattern of behaviour may reflect the different underlying neural causes of the neglect in these patients. In the current study, the measurement of saccades allowed the task to be fractionated, and thus, reveal the action of multiple mechanisms controlling saccades in search. |
Timothy L. Hodgson; Dominic J. Mort; M. M. Chamberlain; Samuel B. Hutton; K. S. O'Neill; Christopher Kennard Orbitofrontal cortex mediates inhibition of return Journal Article In: Neuropsychologia, vol. 40, no. 12, pp. 1891–1901, 2002. @article{Hodgson2002, Recent accounts have proposed that orbitofrontal cerebral cortex mediates the control of behavior based on emotional feedback and its somatic correlates. Here, we describe the performance of a patient with circumscribed damage to orbitofrontal cortex during a task that requires switching between sensory-motor mappings, contingent on the occurrence of positive and negative reward feedbacks. In this test, normal subjects and other patients with prefrontal damage show an increase in latencies for eye movements towards locations at which a negative feedback was presented on the preceding trial. In contrast, our patient does not show this reward-dependent inhibition of return effect on saccades. She was also found to make an increased rate of ocular refixations during visual search and used a disorganized search strategy in a token foraging task. These findings suggest that orbital regions of the prefrontal cortex mediate an inhibitory effect on actions directed towards locations that have been subject to negative reinforcement. Further, this mechanism seems to play a role in controlling natural search and foraging behavior. |
Timothy L. Hodgson; B. Tiesman; Adrian M. Owen; Christopher Kennard Abnormal gaze strategies during problem solving in Parkinson's disease Journal Article In: Neuropsychologia, vol. 40, no. 4, pp. 411–422, 2002. @article{Hodgson2002a, We have taken a novel approach to the study of problem solving involving the detailed analysis of natural scanning eye movements during the 'one touch' Tower of London task. Control subjects and patients with idiopathic Parkinson's disease (PDs) viewed a series of pictures depicting two arrangements of coloured balls in pockets within the upper and lower halves of a computer display. The task was to plan (but not execute) the shortest movement sequence required to rearrange the balls in one half of the display (the Workspace) to match the arrangement in the opposite half (the Goalspace) and indicate the number of moves required for problem solution. As problem complexity increased, control subjects spent proportionally more time fixating the Workspace region. This pattern was found regardless of whether subjects were instructed to solve problems by rearranging balls in the lower or upper visual fields. The distribution of gaze within the Workspace was also found to be problem dependent, with gaze being selectively directed towards the problem critical balls. In contrast, PDs were found to make more errors in the task and failed to show any dissociation in the amount of time fixating the two halves of the display. This pattern suggests that the patients had difficulty in encoding and/or maintaining current goals during problem solving, consistent with a role for fronto-striatal circuits in mechanisms of working memory and attention. |
Sunila Jain; Frank A. Proudlock; Cris S. Constantinescu; Irene Gottlob Combined pharmacologic and surgical approach to acquired nystagmus due to multiple sclerosis Journal Article In: American Journal of Ophthalmology, vol. 134, no. 5, pp. 780–782, 2002. @article{Jain2002, PURPOSE: To describe a combined pharmacological and surgical approach to treating acquired nystagmus in a patient with multiple sclerosis. DESIGN: Interventional case report. METHODS: A 40-year-old patient with acquired horizontal and vertical nystagmus and severe oscillopsia secondary to multiple sclerosis had combined treatment with gabapentin and a vertical Kestenbaum-type procedure. RESULTS: After gabapentin treatment (3,000 mg orally daily) the horizontal nystagmus was significantly reduced, and the patient developed a marked chin-up position. The vertical nystagmus remained unchanged, dampening on downgaze. A recession of both inferior rectus muscles reduced the nystagmus significantly in primary position, the abnormal head position disappeared, and oscillopsia completely resolved. Treatment increased visual acuity from 6/24 in the right eye and 6/60 in the left eye to 6/9 in both eyes. CONCLUSIONS: Acquired nystagmus in multiple sclerosis can be significantly improved by using a combined pharmacological and surgical approach. |
Elliot M. Frohman; Teresa C. Frohman; Padraig O'Suilleabhain; H. Zhang; K. Hawker; M. K. Racke; W. Frawley; J. T. Phillips; Phillip D. Kramer Quantitative oculographic characterisation of internuclear ophthalmoparesis in multiple sclerosis: The versional dysconjugacy index Z score Journal Article In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 73, pp. 51–55, 2002. @article{Frohman2002, Background: There is a poor correlation between multiple sclerosis disease activity, as measured by magnetic resonance imaging, and clinical disability. Objective: To establish oculographic criteria for the diagnosis and severity of internuclear ophthalmoparesis (INO), so that future studies can link the severity of ocular dysconjugacy with neuro- radiological abnormalities within the dorsomedial brain stem tegmentum. Methods: The study involved 58 patients with multiple sclerosis and chronic INO and 40 normal sub- jects. Two dimensional infrared oculography was used to derive the versional dysconjugacy index (VDI)—the ratio of abducting to adducting eye movements for peak velocity and acceleration. Diagnostic criteria for the diagnosis and severity of INO were derived using a Z score and histogram analysis, which allowed comparisons of the VDI from multiple sclerosis patients and from a control population. Results: For a given saccade, the VDI was typically higher for acceleration v velocity, whereas the Z scores for velocity measures were always higher than values derived from comparable acceleration VDI measures; this was related to the greater variability of acceleration measures. Thus velocity was a more reliable measure from which to determine Z scores and thereby the criteria for INO and its level of severity. The mean (SD) value of the VDI velocity derived from 40 control subjects was 0.922 (0.072). The highest VDI for velocity from a normal control subject was 1.09, which was 2.33 SD above the normal control mean VDI. We therefore chose 2 SD beyond this value (that is, a Z score of 4.33) as the minimum criterion for the oculographic confirmation of INO. Of patients thought to have unilateral INO on clinical grounds, 70% (16/23) were found to have bilateral INO on oculographic assessment. Conclusions: INO can be confirmed and characterised by level of severity using Z score analysis of quantitative oculography. Such assessments may be useful for linking the level of severity of a specific clinical disability with neuroradiological measures of brain tissue pathology in multiple sclerosis. I |
2001 |
Elliot M. Frohman; Teresa C. Frohman; J. Fleckenstein; M. K. Racke; K. Hawker; Phillip D. Kramer Ocular contrapulsion in multiple sclerosis: Clinical features and pathophysiological mechanisms Journal Article In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 70, no. 5, pp. 688–692, 2001. @article{Frohman2001, The objective was to describe in multiple sclerosis, a cerebellar eye movement syndrome that resulted from an acute episode of inflammatory demyelination. Contrapulsion is an ocular motor disturbance characterised by a triad of (1) hypermetric saccadic eye movements in a direction opposite from a precisely localised lesion within a specific white matter pathway, the uncinate fasciculus, at the level of the superior cerebellar peduncle (SCP); (2) hypometric saccades towards the side of the lesion; (3) oblique saccades directed away from the side of the lesion on attempted vertical saccades. Infrared oculography was used to demonstrate the characteristic features of contrapulsion in two patients with multiple sclerosis. Brain MRI showed lesions within the region of the uncinate fasciculus and superior cerebellar peduncle in both patients. Eye movement recordings showed saccadic hypermetria away from the side of the lesion and saccadic hypometria towards the side of the lesion. The hypometria decomposed into a series of stepwise movements as the eye approached the target. Oblique saccades directed away from the side of the lesion were seen on attempted vertical saccades. In conclusion, ocular contrapulsion can be seen in patients with multiple sclerosis and results from a lesion in the region of the SCP, involving the uncinate fasciculus. |
Elliot M. Frohman; H. Zhang; Phillip D. Kramer; J. Fleckenstein; K. Hawker; M. K. Racke; Teresa C. Frohman MRI characteristics of the MLF in MS patients with chronic internuclear ophthalmoparesis Journal Article In: Neurology, vol. 57, no. 5, pp. 762–768, 2001. @article{Frohman2001a, OBJECTIVE: The authors imaged the medial longitudinal fasciculus (MLF) in 58 patients with MS and chronic internuclear ophthalmoparesis (INO) to determine which MRI technique best shows the characteristic lesion associated with this ocular motor syndrome. METHODS: Using quantitative infrared oculography, the authors determined the ratios of abduction to adduction for velocity and acceleration, to confirm the presence of INO and to determine the severity of MLF dysfunction in 58 patients with MS and INO. Conventional MRI techniques, including proton density imaging (PDI), T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR) imaging, were used to ascertain which technique best shows MLF lesions within the brainstem tegmentum. T1-weighted imaging was performed to determine the frequency of brainstem tegmentum hypointensities. RESULTS: All patients studied had evidence of an MLF lesion hyperintensity on PDI, whereas T2-weighted imaging and FLAIR imaging showed these lesions in 88% and 48% of patients, respectively. With PDI, dorsomedial tegmentum lesions were seen in the pons in 93% of patients and in the midbrain of 66% of patients. Lesions were observed at both locations in 59% of patients. One patient had an MLF lesion with a corresponding T1 hypointensity. CONCLUSIONS: PDI best shows the MLF lesion in patients with MS and INO. |
Adrienne L. LeVasseur; J. Randall Flanagan; Richard J. Riopelle; Douglas P. Munoz Control of volitional and reflexive saccades in Tourette's syndrome Journal Article In: Brain, vol. 124, pp. 2045–2058, 2001. @article{LeVasseur2001, Tourette's syndrome is characterized by involuntary tics and, although the underlying pathogenesis and patho- physiology of Tourette's syndrome remains unclear, it is suspected that basal ganglia structures are involved. The basal ganglia also play an important role in the control of saccadic eye movements and we therefore hypothesize that Tourette's syndrome patients have abnormal control of saccadic eye movements. In this study, 10 subjects with Tourette's syndrome and 10 age- and sex-matched controls performed four different oculomotor paradigms requiring the execution and/or suppression of reflexive and/or voluntary saccades. In the immediate saccade tasks, sub- jects were required to look either toward (pro-saccade task) or away from (anti-saccade task) a peripheral target as soon as it appeared. In the delayed saccade tasks, subjects were instructed to wait for a central fixation point to disappear before initiating eye movements. Among Tourette's syndrome subjects, saccadic reaction times were longer in all tasks. Saccadic amplitudes were smaller in Tourette's syndrome subjects, and they made more saccades to reach the eccentric target. The occurrence of direction errors (i.e. reflexive pro-saccades on anti-saccade trials) was normal in the immediate anti-saccade task, suggesting that the ability to inhibit reflexive saccades towards novel stimuli was not impaired in Tourette's syndrome. Timing errors (i.e. eye movements made prior to disappearance of the central fixation point in delayed saccade tasks) were significantly greater among Tourette's syndrome subjects. Moreover, these errors were predominantly made towards the first target of the remembered sequence in a delayed memory-guided sequential saccade task. These results indicate that the ability to inhibit or delay planned motor programmes is significantly impaired in Tourette's syndrome. We hypothesize that altered cortical–basal ganglia circuitry leads to reduced cortical inhibition making it harder for Tourette's syndrome subjects to withhold the execution of planned motor programmes. |
Masud Husain; Sabira K. Mannan; Timothy L. Hodgson; Ewa Wojciulik; Jon Driver; Christopher Kennard Impaired spatial working memory across saccades contributes to abnormal search in parietal neglect Journal Article In: Brain, vol. 124, no. 5, pp. 941–952, 2001. @article{Husain2001, Visual neglect of left space following right parietal damage in humans involves a lateral bias in attention, apparent in many search tasks. We hypothesized that parietal neglect may also involve a failure to remember which locations have already been examined during visual search: an impairment in retaining searched locations across saccades. Using a new paradigm, we monitored gaze during search, while simultaneously probing whether observers judged they had found a new target, or judged instead that they were re-fixating a previously examined target. A patient with left neglect following focal right parietal infarction repeatedly re-fixated right locations. Critically, he often failed to remember that these locations had already been searched, treating old targets as new discoveries at an abnormal rate. In comparison, healthy age-matched control subjects rarely re-fixated targets, and mistook old targets as new targets even more rarely. The frequency of such mistakes in the parietal patient, for different conditions, correlated with the severity of his neglect. Control experiments indicated no perceptual localization deficit in non-search tasks. These results suggest a deficit in retaining searched locations across saccades in parietal neglect, in addition to the lateral spatial bias. Moreover, the former deficit exacerbates the latter, such that patients do not realize that the rightward locations favoured by their bias have already been examined during previous fixations and, for this reason, they saccade back to them repeatedly. The combination of the two deficits (a lateral bias plus a deficit in retaining locations already searched) may thus explain the pathological pattern of search that characterizes parietal neglect: why stimuli on the right are re-examined recursively, as if being searched for the first time, and hence why stimuli on the left continue to be ignored even with unlimited viewing time. These proposals accord with recent electrophysiological and functional imaging data, demonstrating posterior parietal involvement in the retention of target locations across saccades. |
Nomdo M. Jansonius; Ton (A) M. Vliet; Frans W. Cornelissen; Jan Willem R. Pott; Aart C. Kooijman In: Journal of Neuro-Ophthalmology, vol. 21, no. 1, pp. 26–29, 2001. @article{Jansonius2001, An otherwise healthy 15-year-old girl with a congenital nystagmus was evaluated at our department using visual evoked potential recording and magnetic resonance imaging. She appears to have the unique isolated inborn absence of the optic chiasm, described only once before in two unrelated girls. Unlike these previously described cases, our patient does not seem to display a see-saw nystagmus. |
2000 |
Alexander P. Leff; Sophie K. Scott; H. Crewes; Timothy L. Hodgson; A. Cowey; D. Howard; Richard J. S. Wise Impaired reading in patients with right hemianopia Journal Article In: Annals of Neurology, vol. 47, no. 2, pp. 171–178, 2000. @article{Leff2000, A left occipital stroke may result in alexia for two reasons, which may coexist depending on the distribution of the lesion. A lesion of the left lateroventral prestriate cortex or its afferents impairs word recognition ("pure" alexia). If the left primary visual cortex or its afferents are destroyed, resulting in a complete right homonymous hemianopia, rightward saccades during text reading are disrupted ("hemianopic" alexia). By using functional imaging, we showed two separate but interdependent systems involved in reading. The first, subserving word recognition, involved the representation of foveal vision in the left and right primary visual cortex and the ventral prestriate cortex. The second system, responsible for the planning and execution of reading saccades, consisted of the representation of right parafoveal vision in the left visual cortex, the bilateral posterior parietal cortex (left > right), and the frontal eye fields (right > left). Disruption of this distributed neural system was demonstrated in patients with severe right homonymous hemianopia, commensurate with their inability to perform normal reading eye movements. Text reading, before processes involved in comprehension, requires the integration of perceptual and motor processes. We have demonstrated these distributed neural systems in normal readers and have shown how a right homonymous hemianopia disrupts the motor preparation of reading saccades during text reading. |
Chiang-Shan Ray Li; Mon-Chu Chen; Yong-Yi Yang; Hsueh-Ling Chang; Chia-Yih Liu; Seng Shen; Ching-Yen Chen Perceptual alternation in obsessive compulsive disorder - implications for a role of the cortico-striatal circuitry in mediating awareness Journal Article In: Behavioural Brain Research, vol. 111, no. 1-2, pp. 61–69, 2000. @article{Li2000, Mounting evidence suggests that obsessive compulsive disorder (OCD) results from functional aberrations of the fronto-striatal circuitry. However, empirical studies of the behavioral manifestations of OCD have been relatively lacking. The present study employs a behavioral task that allows a quantitative measure of how alternative percepts are formed from one moment to another, a process mimicking the brain state in which different thoughts and imageries compete for access to awareness. Eighteen patients with OCD, 12 with generalized anxiety disorder, and 18 normal subjects participated in the experiment, in which they viewed one of the three Schroder staircases and responded by pressing a key to each perceptual reversal. The results demonstrate that the patients with OCD have a higher perceptual alternation rate than the normal controls. Moreover, the frequency of perceptual alternation is significantly correlated with the Yale-Brown obsessive compulsive and the Hamilton anxiety scores. The increase in the frequency of perceptual reversals cannot easily be accounted for by learning or by different patterns of eye fixations on the task. These results provide further evidence that an impairment of the inhibitory function of the cortico-striatal circuitry might underlie the etiology of OCD. The implications of the results for a general role of the cortico-striatal circuitry in mediating awareness are discussed. |
Diane C. Gooding; Jeffrey A. Grabowski; Christian S. Hendershot Fixation stability in schizophrenia, bipolar, and control subjects Journal Article In: Psychiatry Research, vol. 97, no. 2-3, pp. 119–128, 2000. @article{Gooding2000, A few investigators have suggested that visual fixation abnormalities may serve as an endophenotype of liability for schizophrenia. However, the data are equivocal. Conflicting reports regarding the specificity of fixation deficits to schizophrenia may be attributable to methodological differences. Thirty-four schizophrenia patients, 20 bipolar patients, and 30 non-patient controls were presented targets for central fixation. Fixation was scored in terms of frequency of saccades as well as qualitative ratings. Analysis of variance on the number of saccades produced during fixation revealed that the three groups did not differ. Similarly, we observed that the schizophrenia patients did not differ from either bipolar patients or controls in terms of ratings of fixation quality. It appears that schizophrenia patients are not characterized by poor visual fixation. The findings are discussed in terms of the viability of visual fixation as a marker of schizophrenic diathesis, as well as possible implications for the analysis of schizophrenia patients' visual search performance. |
Arthur F. Kramer; Sowon Hahn; David E. Irwin; Jan Theeuwes Age differences in the control of looking behavior: Do you know where your eyes have been? Journal Article In: Psychological Science, vol. 11, no. 3, pp. 210–217, 2000. @article{Kramer2000, Previous research has shown that during visual search young and old adults' eye movements are equivalently influenced by the appearance of task-irrelevant abrupt onsets. The finding of age-equivalent oculomotor capture is quite surprising in light of the abundant research suggesting that older adults exhibit poorer inhibitory control than young adults on a variety of different tasks. In the present study, we examined the hypothesis that oculomotor capture is age invariant when subjects' awareness of the appearance of task-irrelevant onsets is low, but that older adults will have more difficulty than young adults in inhibiting reflexive eye movements to task-irrelevant onsets when awareness of these objects is high. Our results were consistent with the level-of-awareness hypothesis. Young and old adults showed equivalent patterns of oculomotor capture with equiluminant onsets, but older adults misdirected their eyes to bright onsets more often than young adults did. |
1999 |
Gillian A. O'Driscoll; Chawki Benkelfat; Patrik S. Florencio; Anne-Lise V. G. Wolff; Ridha Joober; Samarthji Lal; Alan C. Evans Neural correlates of eye tracking deficits in first-degree relatives of schizophrenic patients Journal Article In: Archives of General Psychiatry, vol. 56, no. 12, pp. 1127–1134, 1999. @article{ODriscoll1999, BACKGROUND: Schizophrenia is thought to arise from the interaction of genetically mediated and environmentally triggered abnormalities in brain function. Reduced frontal activation, reported in schizophrenic patients, may be one expression of genetic risk. The present study investigated whether frontal activation in relatives of schizophrenic patients would be related to eye tracking deficits (ETD), which are considered a behavioral marker of risk for schizophrenia. METHODS: Subjects were first-degree relatives of schizophrenic patients (n = 17) and controls (n = 11). Relatives were divided into those with normal and abnormal pursuit based on qualitative ratings. Subjects were scanned using positron emission tomography and the H(2)15O bolus subtraction technique while performing smooth pursuit and fixation. Brain areas more active in pursuit than fixation were identified in the 3 groups. Correlations were used to investigate the relationship between activation of pursuit regions and pursuit gain in the relatives. RESULTS: Controls significantly activated frontal eye fields (FEFs) and posterior areas, including the motion processing area, V5, and cuneus. The 2 groups of relatives activated the same posterior regions as controls, but differed from each other in activation of FEFs. Relatives with normal tracking activated right dorsal FEFs while relatives with ETD did not. Individual subtractions revealed that 90% of controls and 100% of the relatives with normal tracking activated FEFs during pursuit compared with 42% of relatives with ETD (P = .009). Pursuit gain was significantly and selectively associated with percent activation of right dorsal FEFs (r = 0.74). CONCLUSIONS: Subtle frontal dysfunction seems to be a pathophysiological substrate of ETD in relatives of schizophrenic patients, and may be one aspect of genetically mediated differences in brain function relevant to schizophrenia |