Reduced prefrontal response control in patients with schizophrenias: a subgroup analysis

Visual P3 abnormalities in patients with first-episode schizophrenia, unaffected siblings of schizophrenia patients and individuals at ultra-high risk for psychosis

Cued version of the continuous performance test (AX-CPT) assesses sustained attention, working memory and cognitive control processes, which have been reported as impaired in schizophrenia. This study investigated visual P3 event-related potential elicited during cued CPT in patients with schizophrenia and in individuals who were at clinical or genetic high risk for psychosis to determine whether any abnormality may provide a marker of vulnerability for psychosis. Visual P3 elicited during cued CPT have not been reported in individuals at high risk for psychosis. Visual Go and NoGo P3 potentials were assessed in 34 antipsychotic-naive patients with first-episode schizophrenia (FES), 25 clinically unaffected siblings of these patients (familial high-risk for psychosis, FHR), 49 antipsychotic-naive individuals at ultra-high risk for psychosis (UHR) and 37 healthy control (HC) participants. FES patients had overall smaller P3 amplitudes than all other groups. P3 amplitude of the UHR participants was in-between the HC participants and FES patients. The anteroposterior P3 topography differed between the groups, with FES patients and FHR participants showing a more frontally distributed P3 compared with the HC participants. These findings suggest that the reduction in visual P3 amplitude may provide a vulnerability marker for psychosis in individuals who are at clinical high risk for psychosis and that a more frontally distributed visual P3 may be a marker of genetic liability for psychosis.

Deficits in Go and NoGo P3 potentials in patients with schizophrenia

Cognitive control processes elicited during a cued continuous performance test were evaluated using event-related potentials in 46 patients who were within the first 5 years of diagnosis of schizophrenia, and 29 healthy controls. Patients had longer reaction times, lower hit rates, and higher false alarm rates compared with controls. Patients had an overall P3 amplitude reduction that was more prominent on NoGo compared with Go trials. This greater P3 reduction on NoGo trials was present in central and parietal regions, but was absent in the frontal region, where the P3 reduction was comparable on NoGo and Go trials. Our findings suggest that the neural activity contributing to Go and NoGo P3s are both deteriorated in schizophrenia, but those contributing to central and parietal NoGo P3s are the most severely affected ones. We conclude that the cognitive control processes engaged during execution, and particularly during inhibition of a prepared motor response were disturbed in the early course of schizophrenia. Our findings might be related to our sample being in relatively early stages of schizophrenia and/or related to the use of atypical antipsychotics by most of our patients.

Intact neural activity during a Go/No-go task is associated with high global functioning in schizophrenia

AIM

Go/No-go derived event-related potential (ERP) signals have been widely used in schizophrenia research to monitor self-control deficits in this disorder. However, no study to date has associated Go/No-go-related ERP with global functioning.

METHODS

Participants consisted of 21 patients with schizophrenia and 22 healthy controls. We used a visual Go/No-go paradigm to measure Go/No-go-related N2/P3 ERP components by means of a 64-electrode cap for electroencephalogram recording. We used the Global Assessment of Functioning to evaluate global functioning and analyzed the correlation between ERP indices and global functioning scores.

RESULTS

N2 amplitudes were reduced in patients with schizophrenia, but not influenced by either of the Go/No-go conditions. P3 amplitudes were influenced by the Go/No-go conditions, but not reduced in patients with schizophrenia. Global functioning was correlated with the No-go P3 amplitudes, but not N2 amplitudes, in patients with schizophrenia.

CONCLUSION

These results indicate that global functioning is associated with intact neural activity rather than impaired neural activity during Go/No-go response inhibition tasks in patients with schizophrenia.

Dissociable electrophysiological subprocesses during response inhibition are differentially modulated by dopamine D1 and D2 receptors

Action control is achieved through a multitude of cognitive processes. One of them is the ability to inhibit responses, for which the dopaminergic systems is known to play an important role. Many lines of psychophysiological research substantiate that two distinct response inhibition subprocesses exist, but it has remained elusive whether they can be attributed to distinct neurobiological factors governing the dopaminergic system. We, therefore, investigated this question by examining the effects of DRD1 (rs4532) and DRD2 (rs6277) receptor polymorphisms on electrophysiological correlates of response inhibition subprocesses (i.e., Nogo-N2 and Nogo-P3) in 195 healthy human subjects with a standard Go/Nogo task. The results show that response inhibition performance at a behavioral level is affected by DRD1 and DRD2 receptor variation. However, from an electrophysiological point of view these effects emerge via different mechanisms selectively affected by DRD1 and DRD2 receptor variation. While the D1 receptor system is associated with pre-motor inhibition electrophysiological correlates of response inhibition processes (Nogo-N2), the D2 receptor system is associated with electrophysiological correlates of outcome evaluation processes. Dissociable cognitive-neurophysiological subprocesses of response inhibition are hence attributable to distinct dopamine receptor systems.

Quetiapine and flupentixol differentially improve anterior cingulate cortex function in schizophrenia patients: an event-related potential study

Atypical antipsychotic agents are a frequently and effectively used treatment in schizophrenia and psychotic disorders. Other than conventional antipsychotics, which mainly exert their pharmacological effect in subcortical dopaminergic systems, atypical antipsychotics additionally affect partly serotonergically innervated structures within prefrontal areas, such as the anterior cingulate cortex (ACC). However, only few controlled, randomized studies have so far investigated direct and indirect effects of atypical antipsychotics on the ACC and, up until now, no clinical investigation has exclusively addressed the specific effects of quetiapine on ACC function. The present study assessed ACC function in 18 quetiapine-medicated patients and 13 flupentixol-treated patients suffering from schizophrenia by means of the error-related negativity (ERN), a neurophysiological marker of ACC function, in a pre-post design. Between-group comparisons revealed different effects of quetiapine and flupentixol on ACC function despite similar improvement in psychopathology, cognitive performance and quality of life. Whereas atypical treatment was associated with an increase in amplitudes over time, there were prolonged ERN peak latencies in patients treated with the typical agent. Moreover, treatment effects depended on baseline prefrontal cortex function in both groups. We conclude that both flupentixol and quetiapine improve prefrontal function especially in patients with weak initial ACC function which might be due to their shared affinity for serotonin receptors in frontal brain regions. However, since this affinity is more pronounced for quetiapine, patients treated with quetiapine seemed to profit more evidently concerning their prefrontal cortex function compared to patients of the flupentixol group, who exhibited a compensatory prolongation of processes.

Reduced NoGo-anteriorisation during continuous performance test in deletion syndrome 22q11.2

Deletion syndrome 22q11.2 (DS22q11.2) is a high-risk factor for psychiatric disorders. Alterations in brain morphology and function including the anterior cingulate cortex (ACC) are suggested to underlie the increased psychiatric disposition. We assessed response-inhibition in patients with DS22q11.2 (n=13) and healthy controls (n=13) matched for age, sex, and handedness by means of a Go-NoGo-Task during recording of a multi-channel electroencephalography (EEG). Analysis of event-related potentials (P300) resulted in an aberrant topographical pattern and NoGo-anteriorisation (NGA) as a parameter of medial prefrontal function was significantly reduced in patients with DS22q11.2 compared to controls. Differences in IQ between groups did not account for the findings. Source localization analysis (LORETA) revealed diminished left temporal brain activation during the Go-condition, but no altered ACC activation in DS22q11 during the NoGo-condition. Despite recent reports of structural alterations of the ACC in DS22q11.2 our findings suggest that response-inhibition mediated by the ACC is not impaired in DS22q11.2.