An event-related potential study of prepotent motor activity and response inhibition deficits in schizophrenia.

Response inhibition deficits in schizophrenia (SZ) are accompanied by reduced neural activities using event-related potential (ERP) measurements. However, it remains unclear whether the reduction in inhibition-related ERPs in SZ is contingent upon prepotent motor tendencies. This study aimed to examine the relationship between ERP markers of prepotent motor activity (lateralised readiness potential, LRP) and response inhibition (P3) by collecting behavioural and EEG data from healthy control (HC) subjects and SZ patients during a modified Go/No-Go task. A trial-averaged analysis revealed that SZ patients made more commission errors in No-Go trials compared with HC subjects, although there was no significant difference in the inhibition-related P3 effect (i.e. larger P3 amplitudes in No-Go compared with Go trials) between the two groups. Subsequently, No-Go trials were sorted and median-split into bins of stronger and weaker motor tendencies. Both HC and SZ participants made more commission errors when faced with stronger motor tendencies. The LRP-sorted P3 data indicated that HC subjects exhibited larger P3 effects in response to stronger motor tendencies, whereas this trial-by-trial association between P3 and motor tendencies was absent in SZ patients. Furthermore, SZ patients displayed diminished P3 effects in No-Go trials with stronger motor tendencies but not in trials with weaker motor tendencies, relative to HC subjects. Taken together, these findings suggest that SZ patients are unable to dynamically adjust inhibition-related neural activities in response to changing inhibitory control demands and emphasise the importance of considering prepotent motor activity when investigating the neural mechanisms underlying response inhibition deficits in SZ.