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

To start by looking back a little, recall that even a small brain lesion, if critically located in the left or language hemisphere, may selectively destroy a person's ability to read, while at the same time sparing speech and the ability to converse. The printed page continues to be seen, but the words have lost their meaning. This condition typically follows from focal damage to the angular gyrus in the left hemisphere. It also results from lesions interruptingt he neural input to this left angular gyrus from the visual or calcarine cortical areas (1, 2). It is natural to conclude in such cases that the left hemisphere is responsible for reading while the undamaged right hemisphere, in contrast, must be "wordblind" or incapable of seeing meaning in the printed word.

A simplified technique is described for obtaining lateralization of visual input with prolonged viewing. This technique is based on the presence of constant normal lateral limits for horizontal rotation of the eyes with reference to the head. With head movement prevented by use of a standard bite bar, and the eyes rotated to the left and held at their lateral limit, the temporal half of the visual field of the left eye may be used for lateralized input to the right hemisphere or vice versa for input to the left hemisphere. Any form of visual stimuli or visually monitored task can be used if confined within one of the extreme temporal hemifields. In comparison to previous methods, this technique is technically simple, inexpensive, without significant risk or discomfort to the subject, readily applicable to normal and various brain-lesioned subjects, and permits prolonged in-depth viewing. An alternative version of this technique uses a stabilized spectacle frame fitted with adjustable central occluders set to allow vision through only one or both of the extreme temporal hemifields.

Each hemisphere of two commissurotomy and two hemispherectomy patients was tested separately on the book form of Raven's Standard Progressive Matrice test (RSPM) and on the book, board and tactile forms of Raven's Coloured Progressive Matrices test (RCPM). The two patients who had undergone complete cerebral commissurotomy were tested unilaterally with the aid of a contact lens technique which permits free unilateral ocular scanning and visual guidance. The two other patients had undergone dominant (right) and non-dominant (left) hemispherectomy for post-infantile lesions and were tested in free vision. IQ estimates for the left hemispheres based on RSPM scores ranged from 74 to 103 (mean 87) and right hemisphere IQ estimates ranged from 74 to 93 (mean 83).

In the context of today's mounting global problems the relative demand for medical, educational, and related social benefits that derive from the neurosciences is diminished. At the same time the human value spin-offs of brain research are thrust into a strategic position of top concern because of their key role as criteria or policy priorities and decision-making guidelines. Recent conceptual developments in the mind-brain sciences rejecting reductionism and mechanistic determinism on the one side, and dualisms on the other, clear the way for a rational approach to the theory and prescription of values and to natural fusion of science and religion. Science can be upheld as the best route to an increased understanding and report with the forces that made and move the universe and created man. The outlines of the value-belief system emerge that include an ultimate respect for nature and the evolving quality of the biosphere, which, if implemented, would set in motion the kind of social change needed to lead us out of the viscious spirals of increasing population, pollution, poverty, energy demands, etc. The strategic importance of neuroscience and the central role of prevailing concepts of the mind-brain relation to all of the foregoing remain evident throughout, as does also the direct relevance of efforts to bring added insight and substantiation of these mind-brain concepts through further advances in brain research.

A traditional working hypothesis in neuroscience holds that a complete account of brain function is possible, in principle, in strictly neurophysiological terms without invoking conscious or mental agents; the neural correlates of subjective experience are conceived to exert causal influence but not mental qualities per se. This long established materialist-behaviorist principle has been challenged in recent years by the introduction of a modified concept of the mind-brain relation in which consciousness is conceived to be emergent and causal. Psychophysical interaction is explained in terms of the emergence in nesting brain hierarchies of high order, functionally derived, mental properties that interact by laws and principles different from, and not reducible to those of neurophysiology. Reciprocal upward and downward, interlevel determination of the mental and neural action is accounted for on these terms without violating the principles of scientific explanation and without reducing the qualities of inner experience to those of physiology. Interaction of mind and brain becomes not only conceivable and scientifically tenable, but more plausible in some respects than were the older parallelist and identity views of the materialist position.

The degree to which voluntary maintenance of independent attentional systems in left and right hemispheres during lateralized double simultaneous performances is possible for prolonged periods was assessed in five complete commissurotomy patients, two partial commissurotomy patients and eight normal subjects. Subjects performed a unimanual tactual sorting task as well as bimanual sorting tasks requiring (1) the same, (2) different or (3) opposite simultaneous decisions by left and right hemispheres. Normals were also given additional practice sessions with the same tasks in an effort to determine limitations in the capacity for dual processing. The results suggest that the cerebral commissures force the two hemispheres to work together and maintain attentional unity in the intact brain. Practice increases the capacity for simultaneous processing in normals, but this enhancement is most readily interpreted as the result of automation of performance decreasing the need for attentional supervision rather than as a division of the normal unity of focus in the intact attentional system.

To assess the relative capacities of the two cerebral hemispheres to sustain prolonged mental concentration, the performance of commissurotomized patients and normal controls was tested on monotonous sorting and signal detection tasks. The two series of tasks all required the maintenance of focused attention but differed in the amount of motor activity involved. Results showed that attentional capacity was different for active than for passive tasks in the patient group. During the active sorting tasks, commissurotomy patients were able to sustain continuous attention for periods of up to an hour while in the passive signal detection tasks, a decline in general levels of arousal was evident within ten to twenty minutes. The maintenance of generalized attention with minimal proprioceptive and external stimulation was thus found to be markedly weakened following commissurotomy. Neither hemisphere was consistently inferior to the other in sustaining mental concentration. The unique ability of commissurotomy patients to efficiently carry out mutually conflicting volitional decisions while sorting with the hands simultaneously points up the role of the intact commissures in unifying attentional components of cognitive processing.

Two patients with cerebral commissurotomy were tested with visual input lateralized to left or right half of the visual field by an opaque hemifield screen set in the focal plane of an optical system mounted on a scleral contact lens which allowed prolonged exposure and ocular scanning of complex visual arrays. Key personal and affect-laden stimuli along with items for assessing general social knowledgability were presented among neutral unknowns in visual arrays with 4–9 choices. Selective manual and associated emotional responses obtained from the minor hemisphere to pictures of subject's self, relatives, pets and belongings, and of public, historical and religious figures and personalities from the entertainment world revealed a characteristic social, political, personal and self-awareness comparable roughly to that of the major hemisphere of the same subject.

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