[GABA-B-associated neuropsychiatric disorders].

OBJECTIVE: Disturbed GABA-B mediated inhibitory cortical processes are discussed to be involved both in schizophrenia as well as in chronic tinnitus. Transcranial magnetic stimulation (TMS) provides an intriguing in vivo method to investigate GABA-B associated aspects of cortical inhibition, thus allowing to detect disease-related cortical inhibitory processes. METHOD: Parameters of cortical excitability were measured by TMS in drug-naive first-episode schizophrenic patients and in patients suffering from chronic tinnitus. RESULTS: The cortical silent period as measured by TMS indicated a dysfunctional GABA-B mediated cortical inhibition in both groups of patients. CONCLUSIONS: TMS offers new insights into the pathophysiology of neuropsychiatric disorders. Parameters of this technique point to changes in GABA-B associated inhibitory processes within thalamocortial circuits both in schizophrenia and chronic tinnitus. These data are in line with current models of disturbed thalamic gating in phantom perceptions like auditory hallucinations, chronic tinnitus and central pain.