Smooth Pursuit Eye Tracking Performance Research Articles

Acute and Residual Effects of Marijuana in Humans

Marijuana continues to be the most commonly abused illicit drug in the United States. Because many people abuse marijuana during the evening and on weekends and then go to work or school the next day, more research is needed on the residual effects of marijuana. The current study sought to examine both acute and residual subjective, physiologic, and performance effects of smoking a single marijuana cigarette. Ten healthy male volunteers who reported recent use of marijuana resided on a residential research ward. On three separate days, subjects smoked one NIDA marijuana cigarette containing either 0%, 1.8%, or 3.6% Δ 9-tetrahydrocannabinol (THC) according to a paced puffing procedure. Subjective, physiologic, and performance measures were collected prior to smoking, five times following smoking on that day, and three times on the following morning. Subjects reported robust subjective effects following both active doses of marijuana, which returned to baseline levels within 3.5 h. Heart rate increased and the pupillary light reflex decreased following active dose administration with return to baseline on that day. A new finding was that marijuana smoking acutely produced decrements in smooth pursuit eye tracking. Although robust acute effects of marijuana were found on subjective and physiological measures, and on smooth pursuit eye tracking performance, no effects were evident the day following administration, indicating that the residual effects of smoking a single marijuana cigarette are minimal.

Smooth-pursuit eye movement dysfunction in schizophrenia: the role of attention and general psychomotor dysfunctions.

Smooth-pursuit eye-tracking performance was examined in 100 schizophrenic patients and various control groups under both attention-enhancing and attention-distracting conditions. The level of attentional demand was varied by introducing a secondary reaction time task that directed attention either toward or away from the visual-tracking target. Distraction from the target led to a significant deterioration of tracking performance in all subjects, which was most pronounced in the group of schizophrenic patients. Attention-enhancement, on the other hand, did not normalize performance in this group. In schizophrenic patients, mainly in the distraction condition, there was a moderate association between performance in tracking and tests presumably measuring prefrontal functions. Tracking accuracy from both conditions was related to general motor performance as measured by the Neurological Evaluation Scale. It was concluded that in schizophrenic patients attentional factors (distraction) may contribute to eye-tracking impairment, and that the impairment may be viewed as an aspect of general motor dysfunctions.

The association between lithium carbonate and smooth pursuit eye tracking among first-episode patients with psychotic affective disorders.

The association between treatment with lithium carbonate and smooth pursuit eye tracking performance was investigated in first-episode patients with psychotic affective disorders. The horizontal pursuit performance of patients with major depression and bipolar disorder who were receiving lithium carbonate was contrasted with that of patients not receiving lithium carbonate. In addition, the accuracy and quality of pursuit eye tracking was examined in bipolar patients whose lithium status changed from the time of initial testing to the time of retest 10 months later. For the combined group of depressed and bipolar patients, treatment with lithium carbonate was not associated with worse pursuit performance. Bipolar disordered patients on lithium did not differ in tracking proficiency from those not on lithium; bipolar patients whose lithium status changed from intake to retest also did not display a significant change in pursuit performance.

Clinical, neuropsychological, and brain structural correlates of smooth-pursuit eye tracking performance in chronic schizophrenia.

Clinical, neuropsychological, and brain structural correlates of smooth-pursuit eye tracking performance in chronic schizophrenia.

A model of smooth pursuit performance illustrates the relationship between gain, catch-up saccade rate, and catch-up saccade amplitude in normal controls and patients with schizophrenia

Smooth pursuit eye-tracking performance of 37 unmedicated patients with schizophrenia and 45 normal controls was recorded with infrared oculography, and digitized for offline analysis of gain and other measures. Target velocity was 5°/sec. Patients with schizophrenia had significantly lower gain than normal controls, confirming several earlier reports. During low gain smooth pursuit tracking, when eye velocity is slower than target velocity, the saccadic system corrects for the accumulating position error with catch-up saccades (CUS). The rate of CUS and the median CUS amplitude were compared between groups. Patients had significantly more CUS than controls, but the median CUS amplitudes were not significantly different. A nonlinear mathematical model of the relationship between gain, CUS amplitude, and CUS rate during steady-state constant velocity tracking was developed to integrate these findings. According to this model, for a given gain, correction for position error can result from either a few large CUS or many small CUS. The fit of the model to empirical data, as assessed graphically and with linear and nonlinear regression techniques, was excellent. The model fit the data for both patients and controls. The psychiatric eye-tracking literature is discussed from the perspective suggested by the modeled relationship.

Clinical, neuropsychological, and brain structural correlates of smooth-pursuit eye tracking performance in chronic schizophrenia.

The relation of smooth-pursuit eye tracking dysfunction to neuropsychological performance, brain structural anomalies, and clinical state was examined in a sample of 61 patients with chronic schizophrenia. No association was found between impaired pursuit oculomotion and measures of chronicity or clinical state. Likewise, no association emerged between eye-tracking integrity and brain structural anomalies. Patients with dysfunctional eye tracking were more likely to have impaired performance on tests that assess frontal lobe functioning. In addition, negative symptoms and a relative absence of positive symptoms. Because negative symptoms are often found among patients with frontal lobe impairment, their association with abnormal eye tracking provides converging support for the hypothesis that the cortical locus of deviant smooth-pursuit eye tracking is in the frontal lobes.

The effects of dark adaptation on pursuit tracking dysfunction in psychotics with imparied vestibular suppresion

Smooth pursuit eye tracking performance, evaluated by electronic processing and subjective ratings, was assessed in actively psychotic psychiatric patients and normal controls under conditions of light and dark adaptation and was related to subjects' ability to suppress vestibular nystagmus induced by caloric irrigation. Patients' tracking performance was significantly inferior during the light-adapted condition on all tracking measures. Dark-adaptation eliminated group differences based on electronic analyses, but subjective ratings-which showed a variable relationship to the other tracking measures-did not reflect this improvement. Vestibular nystagmus suppression was significantly impaired in patients relative to controls and this impairment, coupled with smooth pursuit dysfunction and marked improvement in tracking performance during dark-adaptation, suggests that cerebellar dysfunction contributes significantly to tracking dysfunction in psychotic patients.

Features that distinguish the smooth-pursuit eye-tracking performance of schizophrenic, affective-disorder, and normal individuals.

Features that distinguish the smooth-pursuit eye-tracking performance of schizophrenic, affective-disorder, and normal individuals.

Features that distinguish the smooth-pursuit eye-tracking performance of schizophrenic, affective-disorder, and normal individuals.

Features that distinguish the smooth-pursuit eye-tracking performance of schizophrenic, affective-disorder, and normal individuals.

Attention, eye tracking and schizophrenia.

Two experiments are reported. The first experiment successfully replicated the finding that Smooth Pursuit Eye-Tracking(SPET) performance recorded using electronsystagmographic techniques statistically differentiates between groups of clinically diagnosed shizophrenic patients and normal controls. Ratings taken of spontaneous patient behaviour during testing indicated that behaviour which on a priori grounds was thought to preclude optimum attention to eye tracking was related to greater impairment of schizophrenic performance. The second experiment investigated the effect of experimentally induced distraction on SPET performance by normal controls. It was found that competing tasks of increasing levels of difficulty produced increasing degrees of impairment in SPET performance. The results of the two experiments were interpreted as evidence that SPET performance is sensitive to superficial inattention, and that deficits in schizophrenic SPET performance are best explained by attentional deficits in the schizophrenics.