Effects of eye and head position on horizontal and vertical smooth pursuit.

PURPOSE: To identify and explain the effects of eye and head position on smooth pursuit eye movements in normal humans. METHODS: Horizontal and vertical smooth pursuit were measured in different eye-in-orbit positions in normal subjects, using a magnetic search coil technique with sinusoidal and step-ramp stimuli. Pursuit also was tested in different horizontal head-on-trunk positions. RESULTS: Pursuit gain to sinusoidal targets averaged approximately 15% less with the eyes centered 30 degrees horizontally or vertically from the primary position than with the eyes near the orbital midline. In contrast, initial pursuit responses to step-ramp stimuli were similar regardless of eye position. For sinusoidal and step-ramp responses in eccentric eye positions, no significant differences were found between pursuit movements directed toward the orbital midposition and pursuit movements directed away from it. Changes in head position had no effect on smooth pursuit. CONCLUSIONS: Sinusoidal smooth pursuit function decreases modestly for horizontal and vertical motion in eccentric eye positions. This effect is not caused by reductions in gain for centrifugal movements compared to centripetal movements, implying that the pursuit nonlinearities expected to arise from orbital mechanics are largely eliminated by central processing. Eye position-related differences in retinal or eye motion feedback or in predictive input may explain the influence of eye position on smooth pursuit maintenance. Changes in target position with respect to a trunk-centered frame of reference did not produce the orbital eccentricity effects that were documented because sinusoidal pursuit gain did not vary with head rotation.

Concepts and applications of EEG analysis in aviation performance evaluation.

Quantitative studies of the human EEG during signal detection, flight simulation and actual flight performance tasks are reviewed here from the perspective of basic animal research on the neurophysiological and functional correlates of relevant rhythmic patterns. Evidence is examined which relates distinct EEG frequency changes to psychomotor behavior, signal processing and intrinsic attentional modulation during complex performance. Findings indicate that the EEG can provide a valid and objective index for mental effort but, in addition, may reveal task-related cognitive resource allocation, task mastery and task overload.

Quantitative analysis of EEG in boys with attention-deficit-hyperactivity disorder: controlled study with clinical implications.

Sixteen-channel topographic brain mapping of electroencephalograms of 25 right-handed males, 9-12 years of age, with attention-deficit-hyperactivity disorder revealed increased theta (4-7.75 Hz) and decreased beta 1 (12.75-21 Hz) when compared with 27 controls matched for age and grade level. The differences were greater when patients were tested for reading and drawing skills, but were decreased when they were at rest during visual fixation. Although the differences in patients with attention-deficit-hyperactivity disorder were generalized, increased theta was more prominent in frontal regions, while beta 1 was significantly decreased in temporal regions. Principal component analysis was used to combine the variables into 2 components which accounted for 82% of the total variance. A discriminant function analysis using these components was able to predict group membership for attention-deficit-hyperactivity disorder patients 80% of the time and 74% for controls. These findings support the use of topographic electroencephalography for further elucidation of the neurophysiology of attention-deficit-hyperactivity disorder.

Suppression of EEG rhythmic frequencies during somato-motor and visuo-motor behavior.

In a previous study of simulated vehicle performance we found that stationary visual attention and body movements alone produced selective effects on topographic EEG frequency patterns. In the present study we focus on an expanded set of these task components. EEG, EOG and ECG data were recorded from 21 subjects during instructed driving movements and during visual scanning tasks ranging from a stationary to a rapidly moving simulated driving display. Spectral analysis was calculated on ten 2-Hz, partially overlapped frequency bands between 6 and 17 Hz. Body movements produced a selective bilateral suppression of 11-15 Hz activity localized to medial somatosensory cortex, while both slow and rapid visual scanning tasks produced a similar bilateral suppression of 11-15 Hz activity localized to temporo-parietal sites. A generalized suppression of 7-11 Hz activity was also found during the fastest visual scanning task. There were no significant differences in ECG between tasks. Other human and animal findings consistent with these functional observations are discussed.

Multiband topographic EEG analysis of a simulated visuomotor aviation task.

Topographic EEG spectral magnitudes from 19 cortical sites were compared in 15 adult male subjects during performance of a simulated flight task and during control conditions which attempted to separately evaluate functional components of this task. Four conditions were studied, including eyes closed, a visual control, a motor control and a simulated landing task requiring integration of both visual and motor components. Each condition was repeated twice in a counterbalanced replicated measures design. A linked-ear EEG reference was used and spectral magnitudes calculated for 6 frequency bands. Decisions concerning band width and spectral transform were empirically determined. Findings indicated no significant differences between replications. A broad posterior cortical suppression of all frequencies was observed in the visual control condition. Anterior sites were affected only in the 7-12 Hz range. Additional suppression was seen during the motor control condition but limited to frontocentral sites in the 11-13 Hz band. The flight task, however, produced a further suppression at centroparietal cortex in the 9-13 Hz range. The extraction of both attentional and motor components from this task suggests that the parietal EEG activation was specific to cognitive processing.

Differences in semantic event-related potentials in learning-disabled, normal, and gifted children.

Cortical event-related potentials (ERP) were recorded over FZ, CZ, and PZ scalp sites in 15 learning-disabled (LD), 14 gifted (G), and 13 normal control (N) children of ages 8-12. The common stimulus consisted of nouns presented 80 percent of the time; the target stimulus of animal names presented 20 per cent of the time. ERPs were averaged over subjects from 180 msec pre-stimulus to 900 msec post-stimulus. Principal components analysis was used to determine if there were amplitude differences at different post-stimulus latencies as a function of condition. Differences in ERP's between groups (LD, gifted, and controls), scalp locations, and common versus target stimuli were analyzed by ANOVAs. P3, Late, P2, and N1 components represented by four factors were identified. Significant differences between G and LD and the N and LD groups were found target stimulus at all central locations for the P3 component. Differences were found centrally between G and LD, G and N, and N and LD groups for the P2 component centrally. Other differences were found for the N1 and late components. These differences could be interpreted as a deficit in either attentional mechanisms or information processing for the LD group.

EEG correlates of hypnotic susceptibility based upon fast Fourier power spectral analysis.

The purpose of the present study was to determine if there were differences between high and low hypnotic susceptible subjects based upon fast Fourier power spectral analysis of the EEG recorded both before and during hypnotic tasks from frontal-temporal and occipital-parietal locations. Significant differences were obtained based upon EEG recording electrode location, EEG frequency within six different frequency domains, and hypnotic tasks. However, no main effect differences were obtained based upon hypnotic susceptibility. In contrast to some evoked potential studies in which a few differences have been obtained based on hypnotic susceptibility the lack of any EEG differences in this study even when positive and negative hallucination tasks were employed may have implications for the role of the neocortex in mediating hypnotic phenomena.