Callosal transfer in schizophrenia: too much or too little?

Evidence from diverse sources has pointed to an abnormality in callosal transfer in schizophrenia. To examine this further, a test was devised that measures Stroop interference and facilitation within and between the cerebral hemispheres. 46 heterogeneous schizophrenic patients were tested, and it was found that lateralized Stroop effects were equivalent in the left and right hemispheres and did not differ from normal or psychiatric (affective disorder) control Ss. In control Ss, Stroop effects that required interhemispheric transfer of coded information were reduced relative to those requiring intrahemispheric transfer, whereas among schizophrenic Ss, greater Stroop effects were found in the interhemispheric condition, presumably reflecting increased callosal connectivity. An index of callosal transfer did not correlate with gender, age, or IQ in any of the groups, nor did it relate to clinical characteristics in the schizophrenic Ss. The results support a specific functional abnormality of excessive callosal transfer in schizophrenia, though its role in pathogenesis remains unspecified.