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Auditory steady-state responses are larger in patients experiencing auditory verbal hallucinations (AVH) than in never hallucinating subjects (NH) when recorded with open eyes. Compensatory effects were shown for schizophrenic patients when recorded with closed eyes. This effect has not been evaluated in respect to hallucination status.

Gamma responses to 40 Hz stimulation were recorded in 15 AVH patients, 25 healthy controls and 11 NH patients with closed eyes. Mean and peak evoked amplitude and phase-locking index, peak time and maximal frequency were extracted for early- and late-latency responses and compared between groups.

Phase-locking of early, but not late-latency gamma was diminished in schizophrenic patients independently on hallucination status. Peak entrainment time was delayed in hallucinating patients. Magnitude and frequency of early-latency …