However, all patients were taking antipsychotic medication, and its effects must be considered. It has been reported that increased latency does not appear to be related to medication [63], changes in P300 amplitude do not appear to be affected by antipsychotic medication [32], and attenuation of P300 in the frontal areas is greater in unmedicated than medicated patients and during the first episode of schizophrenia [64]. General slowing EEG frequencies has been reported as a consequence of neuroleptic medication, but differences slow wave activity in patients on and off neuroleptic might be the consequence of medication effect but also the consequence of symptom differences [65]. 5-HT promotes the theta rhythm and facilitates learning [66]. In addition, psychopathological states of schizophrenic patients temporally change due to various treatments, and must sufficiently recover so that the MEG examination can be conducted. Further studies on whether ERD/ERS are affected by antipsychotic medication and mental state are needed.
