Failure of language lateralization in schizophrenia patients: an ERP study on early linguistic components

In line with Crow's hypothesis, altered hemispheric lateralization of language would cause the main symptoms of schizophrenia. The present experiment aimed to demonstrate the loss of the hemispheric specialization for linguistic processing in schizophrenia patients at the level of early automatic evoked potentials (N150).

A sample of 10 outpatients with schizophrenia treated with low levels of neuroleptics and 10 matched healthy control subjects were administered 3 linguistic tasks based on stimulus pair comparisons (phonological, semantic and word-picture matching tasks). Laterality scores of early evoked potentials were analyzed during 2 time windows corresponding to the N150- and N400-like components.

The patients failed to develop the typical left hemispheric N150 component evoked by the first word (S1), which was consistently achieved by the healthy control group in posterior sites (p < 0.01). The effect was specific and stable for linguistic stimuli. As well, for the N150 elicited by the target stimulus (S2), the patients exhibited a lack of linguistic lateralization. In the control task (word-picture matching task), in which S2 was a picture, the 2 groups revealed very similar bilateral recognition potentials.

The results point to a failure of language lateralization in patients with schizophrenia, a deficit involving those linguistic networks automatically activated in the earliest phase of word recognition (N150). Consistent with the current view of schizophrenia, this finding may be related to lack of integration among specific processes and reduced interconnection of underlying linguistic networks.