Motor Inhibition Impairments in Schizophrenia and Bipolar Disorder and Neural Functions

Van Voorhuis, Kent, Kang, MacDonald III, and Sponheim (2019) investigated motor inhibition and neural processes using a Stop-Signal Task in patients with schizophrenia, relatives of patients with schizophrenia, patients with bipolar disorder and healthy control subjects while event-related potentials were recorded.

The behavioral results on the task revealed that only the patients with schizophrenia were deficient in reactive inhibition. Patients with bipolar disorder and first-degree relatives of schizophrenia patients performed comparable to healthy control subjects (Van Voorhuis et al., 2019). In this study antipsychotic medication had an influence on the SSRT in the patients with schizophrenia, and they exhibited also longer reaction times as compared to controls, Which is suggestive of an information processing impairment (Van Voorhuis et al., 2019).

The ERP results showed that patients with schizophrenia as well as patients with bipolar disorder showed an enhanced stimulus locked lateralized readiness potential (S-LRP). There was found a significant positive correlation among S-LRP onset latency, RT, and SSRT, which is indicative of a common aspect that precedes the initiation of a common aspect that precedes the initiation of a response which contributes to slower response activation, a slower response completion as well as later motor inhibition. Accordingly, it is suggested that these findings are indicative of slowed processes preceding motor activation (Van Voorhuis et al., 2019).

Both patient groups did show abnormalities in the modulation of the P300 ERP component associated with the probability in case of inhibiting a response. Reduced amplitude of the P300 was related to reaction time as a function of Stop-Signal possibility.

Greater schizotypal symptoms in first-degree relatives of schizophrenia patients was related to diminished responsivity (P300) concerning changes in the probability to response inhibition. It is suggested that the association among schizotypal symptomatology and the modulation of the P300 might be due to a genetic liability for schizophrenia. 

Only the healthy control subjects were not impaired in adjusting time among initiation and completion associated with a stop-signal As measured with the response locked lateralized readiness potential.

An impairment in the modulation of neural processes associated with response inhibition probability as well as the slowing of the selection of a motor response are associated with both schizophrenia and bipolar disorder (Van Voorhuis et al., 2019).