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

The traditional dichotomy that has separated science and value judgment and set corresponding limitations to the domain and role of science is challenged in the context of recent developments in the concept of consciousness and mind-brain relations. A conceptual explanatory model for psychophysical interaction has emerged during the past decade that changes the scientific status of subjective experience and negates many mechanistic, deterministic, and reductionistic features of prior materialist-behaviorist doctrine. Subjective values, conceived in the present terms, transcend their neural components in brain function to become causal determinants per se with objective consequences. The strategic control power of human values functioning as universal cerebral determinants in all social decision making is emphasized, along with logical indications for a more active involvement therein on the part of science. (29 ref)

A 54-item cross-modal visuo-tactile test involving geometrical discriminations in Euclidean, affine, projective and topological space (plane and 3-dimensional) was administered to 7 subjects with commissurotomy, 2 with hemispherectomy, 1 with agenesis of corpus callosum, and to 5 normal controls. Using blind manual stereognosis subjects selected one of a choice of three shapes, screened from sight, that best fitted a set of five different geometrical forms presented together on a panel in free vision. An intuitive apprehension of geometrical relations was involved that did not require formal training in geometry. Findings support a consistent minor hemisphere superiority and disclose orderly differences in left hemisphere capabilities correlated with the different types of geometry.

The long-term effects of cerebral commissurotomy on motor co-ordination and dyspraxia were investigated in 8 patients who had undergone complete or partial commissurotomy 5-10 yr previously. Performance on a series of standardized motor co-ordination and manual dexterity tests was compared with the established norms. Although qualitative performance appeared essentially unimpaired on most tests the scores for speed were consistently below normal and also inferior to those reported for patients with various unilateral brain lesions. In certain bimanual tasks requiring rapid alternating motion and interdependent control severe qualitative and quantitative impairments were present. In addition, marked dysgraphia and mild ideomotor-type dyspraxia on the left side, and moderate dyscopia on the right were present up to 10 yr after surgery in patients with complete commissurotomy. It would appear from the results that interhemispheric communication becomes particularly important for motor output to the extent that the tasks involve complex intermanual coordination or hemispheric specialization with ipsilateral control.

This chapter focuses on the mind-brain relationship. The approach to the mind-brain relation arose largely out of efforts to explain the seeming unity and/or duality of conscious experience in the bisected brain. The chapter focuses on the interpretation of consciousness as an emergent of brain activity. It interprets the emergent conscious properties in terms of conventional neural circuit theory. A further postulate is added to this discussion in which the subjective conscious effect of a brain process is viewed as a functional or operational derivative. In other words, subjective meaning is conceived to depend primarily on the way a given cerebral process works in the context of brain dynamics. The thing that counts in determining a conscious perceptual effect is the preparation to respond to a perceived outside stimulus in an adaptive, meaningful adjustment, rather than the way in which the brain's neural process happens to copy or correspond with the perceived stimulus with respect to shape, size, unity, texture, timing, etc. Conscious phenomena, thus, conceived as dynamic emergent properties of high order cerebral processes, are not merely products of neural complexity, but are also designed specifically to produce operational subjective effects.

The central concepts concerning consciousness that I shall try to defend have already been presented in some detail (Sperry, 1952, 1964, 1965). Accordingly, I shall review them only in brief outline, devoting the bulk of the discussion to various peripheral aspects and implications that previously have had less emphasis. At the outset let me make it clear that when I refer to consciousness I mean that kind of experience that is lost when one faints or sinks into a coma. It is the subjective experience that is lacking during dreamless sleep, that may be obliterated by a blow on the head, by anoxia, or by pressure on the inner walls of the third ventricle during brain surgery. On the positive side we can include as conscious events the various sensations elicitable by a local electric current applied to the unanesthetized brain, or the pain of a phantom amputated limb, as well as most of our waking subjective experience, including self-consciousness.

Ten commissurotomy patients (8 with complete and 2 with partial section of the forebrain commissures) obtained subnormal scores on a battery of 6 standardized tests for assessment of memory. Although the observed memory impairment is presumed to have been amplified by extracommissural brain damage in most of the cases, it is concluded that the loss of the cerebral commissures is mainly responsible and that these commissures serve selective mnestic functions. In particular the data suggest that processes mediating the initial encoding of engrams and the retrieval and read out of contralateral engram elements involve hemispheric cooperation and depend upon the function of the interhemispheric commissures.