Thought disorder in schizophrenia may involve abnormal
semantic activation or faulty working memory maintenance.
Event-related potentials (ERPs) were recorded while sentences
reading “THE NOUN WAS ADJECTIVE/VERB”
were presented to 34 schizophrenic and 34 control subjects.
Some nouns were homographs with dominant and subordinate
meanings. Their sentence ending presented information crucial
for interpretation (e.g., The bank was [closed,
steep]). Greatest N400 activity to subordinate
homograph-meaning sentence endings in schizophrenia would
reflect a semantic bias to strong associates. N400 to all
endings would reflect faulty verbal working memory maintenance.
Schizophrenic subjects showed N400 activity to all endings,
suggesting problems in contextual maintenance independent
of content, but slightly greater N400 activity to subordinate
endings that correlated with the severity of psychosis.
Future research should help determine whether a semantic
activation bias in schizophrenia toward strong associates
is reflected in ERP activity or whether this effect is
overshadowed by faulty verbal working memory maintenance
of context.