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Results for “Eye Movement Measurements”

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At least 91 records · Page 5Linked to original sources
PubMed1998

Distinguishing schizophrenic patients from healthy controls by quantitative measurement of eye movement parameters.

BACKGROUND: Eye tracking dysfunction is a putative trait marker for susceptibility to schizophrenia; however, it cannot be recommended as an additional tool for the diagnosis of schizophrenia, due to low sensitivity and specificity. METHODS: To assess the diagnostic potentials of combinations of eye movement paradigms, four smooth pursuit experiments (1: constant velocity of 15 degrees/sec; 2 and 3: combination with either visual or auditory distractors; 4: constant velocity of 30 degrees/sec) and two saccadic eye movement experiments (1: reflexive saccades; 2: voluntary saccades) were conducted. Fourteen patients with residual schizophrenia and 17 healthy controls were studied. Two sets of discriminant analyses (each with the resubstitution and with the "leaving one out" method) were calculated. RESULTS: In the first set, all 10 characteristic variables were included, whereas for the second set, the three most powerful parameters were selected (two from smooth pursuit tasks and one from a voluntary saccade experiment). This procedure provided the best classification results, regarding concordance between clinical diagnoses and eye movement dysfunction (kappa = .67-.80). CONCLUSIONS: Schizophrenic patients of the residual subtype can be differentiated from healthy individuals with considerable criterion validity on the basis of paradigms from two different ocular motor systems.

Adult↗
PubMed1983

Lateral eye movement as a measure of cognitive ability and style.

Research on lateral eye movements has examined personality and cognitive correlates with the hope of establishing such eye movements as a measure of preference for the different modes of information-processing associated with each of the cerebral hemispheres. Unfortunately, a review of this research provides only conflicting, tenuous substantiation for such hypotheses. The present study attempts to resolve the conflict within previous research by investigating the validity of the measure across a variety of tests of cognitive ability and preference, utilizing several procedures for scoring and classifying subjects on the measure. However, evidence for this measure's ability to predict cognitive performance linked to hemispheric specialization--in any of our conditions--was extremely meager. The usefulness of lateral eye movements as a diagnostic tool must be considered highly suspect; despite this fact, the measure may yet prove to be of some theoretical significance.

Adolescent↗
PubMed2006

Visual search and eye movements in patients with chronic solvent-induced toxic encephalopathy.

Various aspects of visual perception have been found to be impaired in patients with occupational chronic solvent-induced toxic encephalopathy (CSE). The purpose of the study was to characterise the changes in eye movements and visual search performance in CSE patients. We measured eye movements of 13 CSE patients and 22 healthy controls during dynamic visual search task by using a fast video eye tracker. The task was to search for and identify a target letter among numerals presented in a rectangular stimulus matrix (3x3-10x10 items). Threshold search time, i.e. the duration of stimulus presentation required for identifying the target with a given probability was determined by using a psychophysical staircase method. The visual search times of the CSE patients were clearly longer, and they needed considerably more eye fixations than healthy controls to find the target. Thus, their reduced performance in this task was mainly related to the reduction in the number of items which could be processed during a single eye fixation (perceptual span). This reduction probably reflects a limited capacity of visual attention, since visual acuity, contrast sensitivity, and the oculomotor saccade velocity were found to be normal. The results suggest that motor slowness or low-level visual factors do not explain the poor performance of CSE patients in visual search tasks. The results are also discussed with respect to the effects of education, and compared to the performance in the widely used neuropsychological Trail Making Test, which uses similar stimuli and requires visual search.

Aged↗
PubMed2006

Oculomotor tracking strategy in normal subjects with and without simulated scotoma.

PURPOSE: Experiments were conducted on five subjects with no visual impairment to assess tracking strategy differences in subjects with and without a simulated central scotoma. METHODS: Subjects were asked to visually track horizontally moving periodic and nonperiodic sinusoidal stimuli through a +/-5 degrees range. Scotoma simulation was achieved electronically with a closed-loop feedback system using horizontal eye movement measurements from a monocular limbus eye tracker updated at a rate of 500 Hz. The scotoma was centrally located and had defined horizontal half widths of 1, 2, and 3 degrees . Vertical eye position measurements from a video-based dark-pupil tracker were used to identify and remove trials in which extreme vertical eye position deviations reduced the effectiveness of the simulation. RESULTS: All subjects developed a preferred retinal locus (PRL) in the left visual field and demonstrated a tendency for saccadic redirection to this area. Saccadic endpoints into the PRL outnumbered foveally directed saccades by a factor of 2:1. The PRL was located outside the compromised central vision region, typically near the edge of the scotoma boundary, for all subjects except one. This subject had a PRL within the simulated scotoma under two conditions, but the percentage of total time spent at the "compromised" PRL was less than for other subjects. CONCLUSIONS: Subjects with no visual impairment confronted with a central scotoma develop a preferred retinal locus to replace the nonfunctional fovea and appear to suppress normal refoveating saccadic behavior in favor of this location.

Adult↗
PubMed2006

Ocular motor measures in migraine with and without aura.

The purpose of this study was to examine basic ocular motor function in individuals with migraine. We used an infrared eye-tracking system to measure horizontal smooth pursuit to a sinusoidal target, saccades to horizontal target displacements of 5-20 degrees , and the stability of fixation in 19 migraine without aura (MoA), 19 migraine with aura (MA) and 19 headache-free control (C) subjects. Eye movement measurements were made at two target displacement rates and against both homogeneous grey and patterned backgrounds. We found no statistically significant differences between migraine and control subjects in any of the eye movement parameters measured, but did find highly significant effects of both target speed and background pattern in all groups. Our results do not provide support for subclinical cerebellar impairment in migraineurs, and do provide evidence that previously described visual abnormalities in migraine are not artefacts of abnormal fixation or eye movements.

Adult↗
PubMed2005

Visual-vestibular interactions during vestibular compensation: role of the pretectal not in horizontal VOR recovery after hemilabyrinthectomy in rhesus monkey.

Damage to the vestibular labyrinth leads to profound nystagmus and vertigo. Over time, the vestibular-ocular system recovers in a process called vestibular compensation leading to reduced nystagmus and vertigo provided visual signals are available. Our study was directed at identifying sources of visual information that could play a role in vestibular compensation. Specifically, we investigated the role of the pretectal nucleus of the optic tract (NOT) in vestibular compensation after hemilabyrinthectomy (HL) in rhesus monkeys. We chose the NOT because this structure provides critical visual motion information for adaptive modification of the vestibular ocular reflex (VOR). We produced bilateral NOT lesions by injecting the excitotoxin ibotenic acid. We compared vestibular compensation after HL in NOT-lesioned and control animals with intact NOTs. We measured eye movements with an electromagnetic method employing scleral search coils. Measurements included slow-phase eye velocity during spontaneous nystagmus, per- and postrotatory nystagmus and the horizontal VOR (hVOR) gain (eye-velocity/head velocity) associated with per- and postrotatory and sinusoidal (0.2-2.0 Hz; 30-90 degrees/s) whole body oscillation around the earth-vertical axis. VOR gain was low (<0.5) for rotation toward the HL side. Our control animal evinced significant vestibular compensation with VOR gains approaching unity by 100 days post HL. In contrast, monkeys with bilateral lesions of the NOT never obtained this significant recovery with hVOR gains well below unity at 100 days and beyond. Therefore our studies demonstrate that the NOT is an essential source of visual signals for the process of vestibular compensation after HL.

Adaptation, Physiological↗
PubMed2005

The prosodic property of lexical stress affects eye movements during silent reading.

The present study examined lexical stress in the context of silent reading by measuring eye movements. We asked whether lexical stress registers in the eye movement record and, if so, why. The study also tested the implicit prosody hypothesis, or the idea that readers construct a prosodic contour during silent reading. Participants read high and low frequency target words with one or two stressed syllables embedded in sentences. Lexical stress affected eye movements, such that words with two stressed syllables took longer to read and received more fixations than words with one stressed syllable. Findings offer empirical support for the implicit prosody hypothesis and suggest that stress assignment may be the completing phase of lexical access, at least in terms of eye movement control.

Eye Movements↗
PubMed1999

Ethanol impairs saccadic and smooth pursuit eye movements without producing self-reports of sedation.

It has been suggested that eye movements provide a sensitive tool to assess the sedative-like properties of drugs. However, the relationship between sedative-like subjective effects and impairment in eye movements is not clear. For example, it is not clear whether drugs with stimulant-like effects can also impair eye movements. This study evaluated whether ethanol, a drug with both sedative-like and stimulant-like properties, impairs eye movements, and whether the impairment observed after ethanol is related to its sedative properties. Twenty healthy men and women, aged 21 to 35, consumed beverages containing placebo or ethanol (0.4 or 0.8 g/kg) on three separate laboratory sessions, in randomized order. Eye movement and psychomotor and subjective responses were assessed before and at regular intervals for 3 hr after ingestion of the beverage. Subjects were divided post hoc into two groups, based on their sedative-like or stimulant-like subjective responses to ethanol. Nine subjects reported increases in sedative-like effects after ethanol and 11 reported decreases in sedative-like effects, and increases in stimulant-like effects, after alcohol. Despite their distinctly different subjective responses to ethanol, the groups did not differ in the magnitude, time-course or quality of responses on the eye movement measures. In both groups, ethanol decreased peak saccadic eye velocity and smooth pursuit gain. These results demonstrate the dissociation between impairment in eye movements and subjective feelings of sedation after ethanol, and show that eye movements can be impaired even when subjects are reporting stimulant-like effects. The findings suggest that impaired eye movements are not a nonselective index of sedation, but may be related to specific drug actions on brain regions involved in generating these eye movements.

Adult↗