Cognitive Transfer from Right to Left Hemisphere after Section of the Forebrain Commissures

Citation

Myers, Jay J. (1984) Cognitive Transfer from Right to Left Hemisphere after Section of the Forebrain Commissures. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/agst-h905. https://resolver.caltech.edu/CaltechTHESIS:10302018-184155718

Abstract

Transfer of cognitive information from right to left hemisphere was examined in patients with complete surgical section of the forebrain commissures.

A simple new technique is described that allows lateralized presentation of visual input for prolonged viewing by a single hemisphere without attachments to the eye. This technique was applied in tests of the ability of two complete commissurotmy patients to name simple visual and tactual stimuli projected to the right hemisphere and to cross-compare bilateral input, in exception to characteristic disconnection effects. Special procedures and control tests were employed to determine the underlying mechanisms of such behaviors, and especially to assess the involvement of the left hemisphere. Three commissurotomy subjects were also tested for their ability to verbally describe pictures and printed nouns, corresponding to items associated with distinctive tastes and smells, presented for prolonged viewing in the left hemifield.

The commissurotomy patients could sometimes name or cross-integrate the simple stimuli. Use of cognitive strategies and access to stimulus information by the left hemisphere was shown under these conditions. The subjects could not orally name more complex pictures and words. They could, however, provide relevant and appropriate verbal reports including evaluations, category and context cues and even distinct perceptual impressions and other specific associations but not the precise identity.

Results demonstrate that certain cognitive aspects of right hemisphere processing can transfer to the left hemisphere through brainstem channels. Verbalizations in response to stimuli presented in the left visual field and other recent exceptions to symptoms of disconnection may result from this subcortical communication. Other possibilities including oral naming by the right hemisphere cannot account for these results. The name or identity of stimuli is not conveyed by these interhemispheric transmissions but rather, less specific information that is more connotative or orientational in nature. Such transmissions are presumed to function also in normal cognitive processing. The findings provide further evidence for relatively high-level cognitive processing by the right hemisphere.

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