Faculty Bibliography

In terms of cerebral lateralization of function, left-handed persons represent a more heterogeneous group than right-handed persons. Some evidence suggests that left-handed subgroups can be identified on the basis of the following two types of writing posture: (1) inverted posture that indicates ipsilateral hemisphere language capability and (2) straight writing posture that indicates contralateral hemisphere language capability. A direct test of this hypothesis with an intracarotid amobarbital sodium injection failed to support these predictions. For clinical decisions in which the hemisphere subserving language is necessary, one should rely on direct assessment with the use of the amobarbital injection technique

Sensory and cognitive functions were assessed in a right-handed male before and after partial and complete callosal commissurotomy. After the initial posterior section was made, there was no evidence of interhemispheric sensory transfer, although the left hemisphere did have access to stimulus-related semantic and episodic information from the right hemisphere. After the callosum was completely sectioned, this exchange was no longer observed

Two recent patients in our behavioral series investigating the psychological effects of callosal section exhibit right hemisphere language. Using lateralized visual and auditory stimulation, semantic, phonetic, and expressive linguistic functions were examined. While the right hemisphere language systems in both patients were shown to be capable of semantic information processing, they differed in their abilities to process phonetic information, follow verbal commands, and produce linguistic responses. It is argued that the differences between left and right hemisphere language systems are quantitative and are best characterized along a continuum of generative capacity. It is the variability in such capacity that appears to be responsible for the variability in right hemisphere language function within the split-brain population