Electrophysiological evidence for altered early cerebral somatosensory signal processing in schizophrenia.

Various studies have indicated an impairment of sensory signal processing in schizophrenic patients. Anatomical and functional imaging studies have indicated morphological and metabolic abnormalities in the thalamus in schizophrenia. Other results give evidence for an additional role of cortical dysfunction in sensory processing in schizophrenia. Advanced analysis of human median nerve somatosensory evoked potentials (SEPs) reveals a brief oscillatory burst of low-amplitude and high-frequency activity ( approximately 600 Hz), the so-called high frequency oscillations (HFOs). The present study explores the behavior of HFOs in a cohort of schizophrenic patients in comparison to a group of controls. HFOs in the group of patients appeared with a delayed latency. In the low-frequency part of the SEPs an increase in amplitude was found. These results are interpreted to reflect a lack of somatosensory inhibition in the somatosensory pathway, either at a thalamic or a cortical level.