Roger W. Sperry’s research while affiliated with California Institute of Technology and other places

Attempts to clarify a hypothesis of consciousness in which the phenomena of subjective experience are conceived to exert a direct causal influence on brain activity. Response is made to some questions posed by D. Bindra (see PA, Vol. 45:Issue 3) that arose from a recent statement by Sperry of the concept. The aim is to clarify where possible with material that supplements rather than repeats previous accounts, and the hypothesis is compared with other existing theories. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Challenges the assumption that the subjective phenomena of conscious experiences do not exert any causal influence on the sequence of events in the physical brain process. A theory of mind is suggested in which consciousness, interpreted to be a direct emergent property of cerebral activity, is conceived to be an integral component of the brain process that functions as an essential constituent of the action and exerts a directive holistic form of control over the flow pattern of cerebral excitation. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Tests on split-brain animals have suggested that visual information relayed to one eye, and presumably to one hemisphere, is not available to the second hemisphere. The present study was designed to attempt to force the split-brain monkey to integrate visual pattern information across the two hemispheres. A circle and half circle were presented to the monkey through a system of polarized lights and lenses so that each eye saw only two half circles. In order for the animal to be consistently rewarded, he had to select the panel on which a projected full circle was formed. Four monkeys (Macaca nemestrina) were trained as normals and operated on successively (optic chiasm and forebrain commissures). All of the animals eventually relearned the task. A small but persistent deficit in postcriterion performance was observed after the posterior third of the corpus callosum was cut, following earlier transection of the chiasm, anterior commissure and anterior two-thirds of the corpus callosum. Possible mediating mechanisms for such central integration are mentioned.

Five right-handed human subjects in whom the cerebral hemispheres had been surgically deconnected for alleviation of severe epileptic seizures were examined for lateralization of olfaction. As with vision and stereognosis, it was found that olfactory perception may be confined to a single hemisphere when the input is restricted to one side (i.e. to a single nostril). The fact that odors were recognized only in the hemisphere ipsilateral to the nostril stimulated was evidenced by the subject's ability to name odors from the left but not from the right nostril. Non-verbal tests demonstrated perceptual recognition of the right nostril odors in the non-speaking (right) hemisphere. The results were further substantiated in tasks that involved cross-modal olfacto-tactual matchings. Responses were successful when both the tactual and olfactory stimuli projected to the same hemisphere but not if they projected to opposite hemisphere.

[Introduction] Until a few years ago, prevailing views regarding the syndrome of the corpus callosum in man were based very largely on the studies of Akelaitis and his co-workers (Akelaitis et al. 1942; Akelaitis 1944). Using a wide variety of tests Akelaitis examined a series of more than two dozen patients with partial and complete surgical sections of the corpus callosum and anterior commissure and was unable to find any consistent neurological or psychological dysfunctions that could be reliably attributed to the commissural sections. Symptoms such as unilateral astereognosis, alexia, agraphia, ideo-motor apraxia (Sweet 1941), as well as apathy, amnesia, personality changes and related effects, that earlier had been ascribed to callosal lesions (Alpers and Grant 1931) seemed accordingly to be more properly explained in terms of the extracallosal cerebral damage that commonly accompanies lesions in the commissures. These Akelaitis reports in combination with confirmatory observations on absence of symptoms after callosum section in animals established the general doctrine of the 1940's and 1950's in which it was believed that behavioral deficits seen in connection with callosal lesions are best ascribed to associated brain damage (Bremer et al. 1956). Meanwhile, the discrepancy between the enormous size and strategic position of the corpus callosum on the one hand and the observed lack of any important functional disturbance following its complete surgical section on the other remained during this period one of the more puzzling enigmas of neurology.

Describes experiences with advanced epileptics in whom an extensive midline section of the cerebral commissures had been carried out in an effort to contain severe epileptic convulsions not controlled by medication. The most remarkable result of this operation was the apparent lack of effect on ordinary behavior. However, among the most significant symptoms, collectively termed as the syndrome of hemisphere deconnection, was an apparent doubling in most realms of conscious awareness. Each hemisphere seemed to have its own separate and private sensations, perceptions, concepts, and impulses to act, with related volitional, cognitive, and learning experiences. Appartus for studying the lateralization of visual, tactual, lingual, and associated functions in the separated hemispheres is described. Observations led to the opinion that the minor hemisphere constitutes a 2nd conscious entity that is characteristically human and runs along in parallel with the more dominant stream of consciousness in the major hemisphere. (20 ref.)

Monkeys with varying degrees of brain bisection were trained on a visual discrimination that required interhemispheric integration of sensory information for its solution. A matching-to-sample task was used in which the sample was projected to one hemisphere and the two choices for the match were projected to the other hemisphere. Monkeys with complete section of the optic chiasm and forebrain commissures could not solve this task. There was some evidence of interhemispheric integration via portions of the hippocampal commissure or corpus callosum anterior to the splenium. Various strategems unrelated to the visual stimuli were sometimes employed for above-chance performance.