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PubMedDate not supplied

Neuroocular side effects of carbamazepine and phenobarbital in epileptic patients as measured by saccadic eye movements analysis.

The effect of carbamazepine (CBZ) and phenobarbital (PB), alone and in association, on the function of specific brain structures was studied in chronically treated epileptic patients by means of saccadic eye movements (SEMs) analysis. The relationship between daily fluctuations of CBZ plasma levels and the occurrence of intermittent side effects was also evaluated. All treatments produced a significant impairment (p less than 0.001) of SEM function as compared with a group of controls. SEM abnormalities appeared to change in relation to daily fluctuation of CBZ plasma levels. When the SEM parameters were considered separately, PB showed a significantly (p less than 0.001) more relevant sedative effect, whereas both drugs appear to produce the same effect on cerebellar and pontine functions. Although impairment of SEM function was most likely far from reaching clinical significance, it represents important information for the clinician.

Adult↗
PubMed2005

Inhibition of saccade and vergence eye movements in 3D space.

Inhibitory capacity was investigated by measuring the eye movements of normal subjects asked to fixate a central point, and to suppress eye movements toward visual distracters appearing in the periphery or in depth. Eight right-handed young adults performed such a suppression or distracter task. In different conditions, the distracter could appear at 10 degrees left or right at a distance of 20, 40, or 150 cm (calling for horizontal saccades), or in a central position far or close (calling for convergence or divergence), or 7.5 degrees up or down at 40 or 150 cm (calling for vertical saccades). Eye movements were recorded binocularly with an infrared light eye-movement device. Results showed that (1) suppression performance was not perfect, as the subjects still produced eye movements; (2) errors were distributed unequally in three-dimensional space, with more frequent errors toward distracters calling for convergence, or leftward and downward saccades at a close distance; (3) distracters calling for saccade suppression yielded saccades in the direction of the distracter (that we called prosaccades), and saccades directed away from it (that we called spontaneous antisaccades); (4) for vergence, only distracters calling for convergence yielded errors, which were always promovements; (5) in addition, a small convergent drift was found for convergence distracters. Differences in the errors between saccade and vergence suggest that different inhibitory mechanisms may be involved in the two systems. Spatial left/right, up/down, and close/far asymmetries are interpreted in terms of attentional biases.

Adult↗
PubMed2002

The Eyelink Toolbox: eye tracking with MATLAB and the Psychophysics Toolbox.

The Eyelink Toolbox software supports the measurement of eye movements. The toolbox provides an interface between a high-level interpreted language (MATLAB), a visual display programming toolbox (Psychophysics Toolbox), and a video-based eyetracker (Eyelink). The Eyelink Toolbox enables experimenters to measure eye movements while simultaneously executing the stimulus presentation routines provided by the Psychophysics Toolbox. Example programs are included with the toolbox distribution. Information on the Eyelink Toolbox can be found at http://psychtoolbox.org/.

Eye Movements↗
PubMed2006

The time-course of morphological constraints: evidence from eye-movements during reading.

Lexical compounds in English are constrained in that the non-head noun can be an irregular but not a regular plural (e.g. mice eater vs. *rats eater), a contrast that has been argued to derive from a morphological constraint on modifiers inside compounds. In addition, bare nouns are preferred over plural forms inside compounds (e.g. mouse eater vs. mice eater), a contrast that has been ascribed to the semantics of compounds. Measuring eye-movements during reading, this study examined how morphological and semantic information become available over time during the processing of a compound. We found that the morphological constraint affected both early and late eye-movement measures, whereas the semantic constraint for singular non-heads only affected late measures of processing. These results indicate that morphological information becomes available earlier than semantic information during the processing of compounds.

Adult↗
PubMed1991

Qualitative descriptions of error recovery patterns across reading level and sentence type: an eye movement analysis.

Purposes of the present study included describing a variety of error recovery patterns based on eye movement (EM) measures of sentence parsing across reading level and error type. A qualitative pattern analysis of EM mappings was completed for students with reading disabilities (n = 10) and nondisabled students (n = 10) who were parsing control and erred sentences. Independent variables included error type (syntactically ambiguous, semantically anomalous, and control sentences) and reading proficiency level. Dependent variables consisted of seven eye movement measures. Chi-square analyses were performed to examine group differences across frequencies per pattern. Results suggest that the error recovery strategies deployed by both groups were similar in pattern and frequency; patterns were largely organized, strategic, and efficient, as predicted. Evidence for seven newly defined strategies was found, with indications of multiple strategies within sentences by both groups. Strategies tended to be error "reanalysis" (vs. "recovery") heuristics, in that readers from both groups used regressions to reanalyze regions of inconsistency rather than regions of disambiguation. Earlier conclusions regarding disorganized processing and individual differences among adolescents with reading disabilities are discussed.

Attention↗
PubMed1986

Saccadic eye movements analysis as a measure of drug effect on central nervous system function.

Peak velocity (PSV) and duration (SD) of horizontal saccadic eye movements are demonstrably under the control of specific brain stem structures. Experimental and clinical evidence suggest the existence of an immediate premotor system for saccade generation located in the paramedian pontine reticular formation (PPRF). Effects on saccadic eye movements have been studied in normal volunteers with barbiturates, benzodiazepines, amphetamine and ethanol. On two occasions computer analysis of PSV, SD, saccade reaction time (SRT) and saccade accuracy (SA) was carried out in comparison with more traditional methods of assessment of human psychomotor performance like choice reaction time (CRT) and critical flicker fusion threshold (CFFT). The computer system proved to be a highly sensitive and objective method for measuring drug effect on central nervous system (CNS) function. It allows almost continuous sampling of data and appears to be particularly suitable for studying rapidly changing drug effects on the CNS.

Amobarbital↗
PubMed2003

Detection of eye movements from fMRI data.

Awake humans make eye movements with amplitudes and frequencies that depend on behavioral state and task. This poses two problems for functional magnetic resonance imaging (fMRI) studies that compare brain activity across tasks. First, motion of the eye in the orbit increases the variance of the MR signal in adjacent regions of the orbitofrontal cortex, hampering activation detection. Second, eye movements are associated with activity in a distributed network of brain areas, confounding comparisons of task activation. Direct measurement of eye movements in the scanner bore is possible with expensive and technically demanding equipment. A method is described that detects eye movements directly from MR data without the use of additional equipment. Changes in the MR time series from the vitreous of the eye were observed that correlated with eye movements, as measured directly with an infrared pupil tracking system. In each of 10 subjects, the variance of the MR time series from the eye vitreous was greater when the subject made eye movements than when the subject fixated centrally (average standard deviation (SD) 99.7 vs. 75.6, P = 0.001). The assessment of eye movements directly from fMRI data may be especially useful for retrospective and meta-analyses.

Adult↗
PubMed1990

The minimum motion technique applied to determine isoluminance in psychophysical experiments with monkeys.

Isoluminance ratios for red/green, red/blue and blue/green sinusoidal gratings were determined in macaque monkeys using the minimum motion heterochromatic photometry technique (Anstis & Cavanagh, 1983), in which the motion of specially constructed test grating reverses at the point of isoluminance. The point of luminance equality between the two colors was determined using (1) overt responses of monkeys trained to discriminate motion direction and (2) reversals in the direction of the nystagmic eye movements. Both measures yielded essentially identical isoluminance points. Both the spatial and the temporal frequency of the grating patterns were found to influence the isoluminance settings in all animals tested. The amount of blue equating a preset red or green value was found to increase consistently with increased spatial frequency and with increasing eccentricity. These results show the necessity of spatial and temporal frequency dependent adjustment of visual patterns used in psychophysical and physiological experiments dealing with the processing of color. Furthermore, eye movement measurements appear to be sufficiently in order to determine isoluminance in foveally presented moving patterns with nonhuman primates.

Animals↗
PubMed1993

The effects of head and trunk position on torsional vestibular and optokinetic eye movements in humans.

We measured torsional vestibular and optokinetic eye movements in human subjects with the head and trunk erect, with the head supine and the trunk erect, and with the head and trunk supine, in order to quantify the effects of otolithic and proprioceptive modulation. During active head movements, the torsional vestibulo-ocular reflex (VOR) had significantly higher gain with the head upright than with the head supine, indicating that dynamic otolithic inputs can supplement the semicircular canal-ocular reflex. During passive earth-vertical axis rotation, torsional VOR gain was similar with the head and trunk supine and with the head supine and the trunk erect. This finding implies that static proprioceptive information from the neck and trunk has little effect upon the torsional VOR. VOR gain with the head supine was not increased by active, self-generated head movement compared with passive, whole body rotation, indicating that the torsional VOR is not augmented by dynamic proprioceptive inputs or by an efference copy of a command for head movement. Viewing earth-fixed surroundings enhanced the torsional VOR, while fixating a chair-fixed target suppressed the VOR, especially at low frequencies. Torsional optokinetic nystagmus (OKN) evoked by a full-field stimulus had a mean slow-phase gain of 0.22 for 10 degrees/s drum rotation, but gain fell to 0.06 for 80 degrees/s stimuli. Despite this fall in gain, mean OKN slow-phase velocities increased with drum speed, reaching maxima of 2.5 degrees/s-8.0 degrees/s in our subjects. Optokinetic after nystagmus (OKAN) was typically absent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

The relationship of anticipatory smooth eye movement to smooth pursuit initiation.

We measured anticipatory smooth eye movements and smooth pursuit initiation with predictable and unpredictable step-ramp stimuli in normal subjects. Subjects generated anticipatory eye motion before targets moved and during intervals when targets suddenly disappeared. Expectations of target trajectory modified pursuit acceleration and latency, demonstrating that pursuit initiation is not governed by visual inputs alone. Anticipatory smooth eye movements and predictive contributions to smooth pursuit had similar accelerations and velocities. Anticipation and pursuit initiation varied in parallel between subjects; anticipation was stronger in subjects who generated faster smooth pursuit. These findings imply that anticipatory and smooth pursuit eye movements are governed by a common mechanism.

Adult↗
PubMed1982

Saccadic eye movements of schizophrenic patients measured by reflected light technique.

In order to evaluate the integrity of their saccadic system, we have examined saccadic eye movements and smooth pursuit in a small group of schizophrenic patients, using precise infrared recording instrumentation. There were no significant differences between mean saccadic latencies of patients and controls. Both groups had mean latencies within the normal range of 200-250 msec. Saccades of schizophrenic patients appeared to have normal trajectories and dynamic characteristics. Three of the six schizophrenic patients and one of the three normal controls had smooth pursuit tracking characterized by saccadic intrusions and saccadic smooth pursuit tracking. Occasional saccadic intrusions and saccadic smooth pursuit tracking appeared in the records of all other subjects, but with considerably lower frequency. These results, emerging from reflected light methods, confirm a previous report of normal saccadic latencies in schizophrenic patients using an electrooculographic technique.

Adult↗