SPET study of verbal fluency in schizophrenia and epilepsy

The association between temporal lobe epilepsy and schizophrenia suggests that the critical abnormality may be pathology within the temporal lobes. People with schizophrenia-like psychosis of epilepsy (SLPE) provide a useful group in which to examine the importance of temporal and frontal lobe dysfunction in schizophrenia.

A verbal fluency activation paradigm and a 99mTc HMPAO SPET were used to study frontotemporal function in people with SLPE (n = 12), schizophrenia (n = 11) and epilepsy (n = 16).

People with SLPE differed from both other groups by showing lower blood flow in the left superior temporal gyrus during performance of a verbal fluency task compared with a word repetition task (F = 5.4, P = 0.01). During the verbal fluency task people with primary schizophrenia showed a greater increase in blood flow in anterior cingulate (F = 4.5, P = 0.02) than the other two groups. There were no between-group differences in frontal brain regions.

Our findings support an association between left temporal lobe abnormality and SLPE. The different patterns of activation observed in people with primary schizophrenia and SLPE suggests that different pathophysiological mechanisms may operate in these two groups. In SLPE the pathophysiology may be relatively confined to the dominant temporal lobe.