Distinct cortical inhibitory profiles in schizophrenia and bipolar disorder: A TMS-EEG study of GABAb function

EEG recordings associated with transcranial magnetic stimulation (TMS) with paired pulse paradigms allow the in vivo assessment of cortical inhibitory function. The long-interval cortical inhibition (LICI) paradigm can be used to estimate this function related to GABAb receptors.

We compared LICI values between 25 patients with schizophrenia, 16 patients with bipolar disorder (BD), and 23 healthy controls (HC). We also assessed the relationship between LICI values and cognitive performance, as well as the treatment with antipsychotics, benzodiazepines, and anticonvulsants.

LICI was significantly lower in patients with schizophrenia than in controls, but not in BD patients. In the former group, LICI was negatively associated with cognitive performance and positive symptoms. However, benzodiazepines increased LICI values, which does not explain its decrease in schizophrenia patients.

Our data support the existence of a functional inhibitory deficit mediated by GABAb receptors in schizophrenia, that is associated with cognitive performance and symptoms. In the context of existing literature, this deficit may characterize a subgroup of patients with this diagnosis.