Response Inhibition and Emotional Modulation Effect on Response Inhibition in Biopolar I Disorder and Schizophrenia.

Abstract

Response inhibition deficits and the influence of emotion on response inhibition were investigated in patients with schizophrenia (SZ), schizoaffective disorder (SAD) and bipolar I disorder (BD) with event-related brain potentials (ERPs). Further, it was tested whether the neural deficits in response inhibition can differentiate each group by applying discriminant functional analysis. In order to fulfill the study goal, two different versions of Go/NoGo tasks were used: non-affective stimulus (alphabet letters) and the other with affective stimulus (faces with emotions).Two event-related brain potentials (ERPs), N200 and P300 components were measured for non-affective Go/NoGo task, while face-specific ERPs, N170 and N250, in addition to P300, were further obtained for emotional Go/NoGo task . With lateralized non-affective Go/NoGo task, the first study revealed that SZ showed left-lateralized response inhibition deficit over the frontal region measured by P300. SAD showed prolonged stimulus evaluation time in the early stage of response inhibition manifested by N200 latency. The second study replicated SZ’s response inhibition deficit associated with left hemisphere dysfunction. BD disorder did not show deficits in response inhibition compared to that in SZ but delayed overall cognitive stimulus evaluation was observed. When the non-affective stimuli were replaced with faces with four categories of emotions (happy, angry, sad, and neutral), emotion modulation effect (larger ERP amplitudes for faces with emotions than for neutral faces) was observed only in response execution (Go trials) not in response inhibition (NoGo trials) process in both patients and controls. Both SZ and BD showed deficits in early facial structure encoding revealed by reduced amplitude in N170 component but relatively intact in early facial affect decoding compared to healthy controls (CT). In three studies, it was replicated that P300 amplitude and N200 latency successfully discriminated SZ, SAD (study 1), BD (study 2 & 3), and CT, which implicates that distinct ERP patterns in response inhibition task can become endophenotypes of each psychiatric disorder.