An association between reduced interhemispheric EEG coherence in the temporal lobe and genetic risk for schizophrenia (vol 49, pg 129, 2001)

Previous studies have suggested that schizophrenic patients show resting EE G changes such as frequency-slowing and decreased coherence in the frontal and temporal area. We sought to determine whether these findings are also f ound in clinically unaffected siblings of schizophrenics and estimate herit ability by calculating relative risk. We investigated two independent data sets: (1) from the NIMH St. Elisabeths campus (59 schizophrenics, 76 unaffe cted siblings and 32 unrelated normal controls) and (2) from the NIH-campus (Bethesda) (59 schizophrenics, 90 unaffected siblings and 26 unrelated nor mal controls). We computed power spectra and coherence on the first data se t and then tried to replicate the results on the second data set. Power spe ctrum analysis suggested that schizophrenics are cortically hypoactivated, whereas in unaffected siblings, a tendency for hyperactivation was found. I n contrast, spectral coherences (0.5-5 Hz) were reduced in both data sets i n the temporal lobe areas in schizophrenics and in their unaffected sibling s. Changes were most pronounced for the interhemispheric coherence linking both posterior temporal lobe areas. Relative risk calculations (lambda (s)) ranged between 3.7 and 9.8, depending on phenotype definition. Thus, while power spectrum EEG abnormalities may be state-dependent, reduced coherence as a possible measure of neuronal synchronization is familial and potentia lly a heritable trait related to genetic risk for schizophrenia. (C) 2001 E lsevier Science B.V. All rights reserved.