Robert Ornstein

Differential right hemisphere engagement in visuospatial tasks.

Abstract Ten male and ten female normal people performed six spatial tasks and one verbal task while EEG alpha was recorded from parietal and central areas bilaterally. The tasks were controlled to equate gross motor activity and stimulus characteristics across tasks. The spatial tasks engaged the right hemisphere more than the verbal task, withtthe exception of complex mental rotation, which showed an EEG pattern similar to the verbal task. Most of the differences in EEG patterns between tasks were accounted for by differences in right hemisphere engagement. Two unexpected findings were a higher right hemisphere engagement in whole-whole matching compared to part-whole matching, and a high left hemisphere engagement in mental rotation. These unexpected findings may be due to analytic strategies having been used by people performing part-whole matching and mental rotation.

Lateral eye movement and cognitive mode

The direction of lateral eye movement elicited by reflective questions is strongly modified by the cognitive demands of the question; verbal and arithmetical questions elicit more movements to the right than do spatial and musical questions. This is consistent with the lateral specialization of the human brain for these cognitive processes. These results support the hypothesis that the direction of the lateral eye movement indicates the activation of the contralateral cerebral hemisphere.

Individual differences in cognitive style—I. Reflective eye movements☆

Abstract Reflective eye movements were studied in subjects whose vocations emphasize either verbal-analytic or spatial-holistic cognitive modes: lawyers and ceramicists (N=35). Questions demanding verbal or spatial thought were administered, and the first eye movement following the question was scored in both vertical and lateral directions. Lawyers and ceramicists differed only in the vertical direction; more up movements for ceramicists than for lawyers. The effects of question type were studied in this population and in a group of non-specialized subjects (N=19). The results confirm our previous findings: verbal questions evoke more right movements than spatial questions. In addition, verbal questions evoked more down movements than spatial questions.

Sex and handedness differences in EEG measures of hemispheric specialization

Abstract EEG alpha asymmetry was studied in 90 normal adults: right-handed, left-handed, and ambidextrous, male and female. Recordings were made from homologous central, parietal, and occipital leads, referenced to vertex, while subjects engaged in writing, speaking, reading, listening to speech, singing, and block design construction. These data confirm our previous findings that alpha asymmetry is task-dependent and extend them to a broader range of tasks, subjects, and leads. Among right-handers significant differences were found between the language tasks and the musical and spatial tasks: the R L alpha ratio is higher in the language tasks. In addition, significant ordering of R L alpha ratios was found among the language tasks themselves: WRITE a SPEAK > READ > LISTEN. No one “verbal” task can be considered representative of all language behaviors. Task differences in asymmetry were greater at the central than at the parietal leads, and no differences were found at the occiput. Differences among the handedness groups were found in R L alpha ratio in specific tasks, in the relationship among tasks, and in alpha power level. Non-right-handers showed less task-dependent asymmetry. On some measures ambidexters appear to be a distinct group, not simply representing the middle range of a left-handed/right-handed continuum. Reversal of the “expected” right-handed pattern (SPEAK R L ratio > BLOCKS R L ratio) was seen in 10% of right-handers, and in 36% of left-handers, particularly among left-handed females (46%), suggesting a possible sex difference among non-right-handers. No sex difference was found among right-handers on any task with any measure at any lead.