HEMISPHERIC LATERALITY AND INTERHEMISPHERIC DISCONNECTION IN SCHIZOPHRENIA

Abstract

In order to evaluate the hypotheses implicating unilateral hemispheric dysfunction or interhemispheric disconnection in the pathogenesis of schizophrenia, a series of experiments were carried out which examined performances of schizophrenics and normal controls on cognitive tasks of various sensory modalities such as 1) manual discrimination of sandpaper texture, 2) manual discrimination of weights, 3) manual recognition of random-shaped objects and 4) visual identification and matching of letters and shapes (divided visual field technique).Results of the first three experiments on manual tasks were straightforward supporting neither of these hypotheses. On the other hand, the last divided visual field experiments yielded rather complicated and inconsistent results. In one series, results were partly in agreement with the left hemisphere dysfunction and interhemispheric disconnection hypotheses, while in another series, results were rather in accordance with the right hemisphere dysfunction hypothesis but quite inconsistent with the disconnection hypothesis. The major reason for the contradictions between both series was presumed to be the different visual angles of stimulus presentation. Furthermore, on dividing the subjects into right-eyed and left-eyed subgroups, a striking difference emerged between the two, suggesting that the latter has a less lateralized, diffuse brain organization, as do schizophrenic patients on the whole.Altogether, our study casts doubt on the lateralized hemisphere dysfunction and interhemispheric disconnection hypotheses, instead favoring the diffuse brain organization hypothesis of schizophrenia.