Alteration of interhemisphere conduction through corpus callosum in chronic schizophrenia

The contralateral and ipsilateral somatosensory evoked potentials (SEP) after stimulation of the right and left median nerve were recorded in 10 patients with chronic schizophrenia and in 10 normal subjects. The ipsilateral SEP depends on the function of the corpus callosum. The latency-delay from peak 5 in the contralateral SEP to the analogous peak in the ipsilateral SEP was significantly reduced in the patients, but only from the left to the right hemisphere. This peak presumably represents interhemisphere transfer and function of corpus callosum. The amount of synaptic activity--measured by the mean amplitude of the SEP--in the right hemisphere, relative to the activity in the left hemisphere after stimulation of the right median nerve, was also greater in the patients. These differences could be interpreted as an abnormal function of the corpus callosum and as a breakdown of the lateral specialization of the left cerebral hemisphere in schizophrenia.