Tachistoscopic tests of colour naming and matching in schizophrenia: evidence for posterior callosum dysfunction?

Neuropsychological studies have shown that the integrity of the posterior corpus callosum is necessary for accurate colour naming in the left visual field (LVF) and colour matching across hemifields. Using this model, 22 schizophrenics, 14 depressive and 16 healthy matched controls were given a battery of tachistoscopic tests of colour perception. The schizophrenics made significantly more errors, in naming colours in the LVF compared to depressives, and in matching colours across fields compared to depressives and normals. There were no differences between groups for right visual (RVF) colour naming or matching within right and left visual fields. These findings support the hypothesis that trans-callosal transmission may be impaired in schizophrenia and are unlikely to be due to a specific disorder of colour perception, neuroleptic drugs or generally impaired performance. Those schizophrenics whose LVF naming errors exceeded RVF errors were more likely to have first rank symptoms and showed less cerebral atrophy but did not differ on other variables. The techniques described may be useful for further research into interhemispheric function in schizophrenia.