Euthymic bipolar disorder (euBD) patients exhibit deficits in neurocognitive and social cognitive functioning compared to healthy controls (HCs). Our prior research has shown that the excitatory/inhibitory (E/I) imbalance in the default mode network (DMN) is linked to executive function in euBD. Neurocognitive impairments are associated with social cognition deficits in individuals with mental disorders. Given this connection, this study posits E/I imbalance within the DMN is associated with social cognition, with executive function as a mediator.

Seventy-five HCs and 49 euBD individuals were recruited. Using the emotion recognition task, Diagnostic Analysis of Nonverbal Accuracy 2-Taiwan version (DANVA-2-TW) and cognitive flexibility task, Wisconsin Card Sorting Test (WCST), we assessed emotion recognition and prefrontal function. Proton magnetic resonance spectroscopy (1H-MRS) measured metabolites in the posterior cingulate cortex (PCC) and medial prefrontal cortex/anterior cingulate cortex (mPFC/ACC), quantifying excitatory glutamate+glutamine (Glx) and inhibitory GABA to calculate the E/I ratio.

euBD patients showed poorer emotion recognition (p = 0.020) and poorer cognitive flexibility (fewer WCST categories completed, p = 0.002). A negative association was found between emotion recognition and the E/I ratio in the mPFC/ACC of the BD patients (r = −0.30, p = 0.034), which was significantly mediated by cognitive flexibility (Z = −2.657, p = 0.007).

The BD patients demonstrate deficits in emotion recognition, linked to an altered E/I balance in the prefrontal cortex, and the cognitive flexibility, a key aspect of executive function, mediates the impact of the E/I ratio on emotion recognition accuracy in euBD patients.

Targeting the glutamatergic system is posited as a potentially novel therapeutic strategy for psychotic disorders. While studies in subjects indicate that antipsychotic medication reduces brain glutamatergic measures, they were unable to disambiguate clinical changes from drug effects.

To address this, we investigated the effects of a dopamine D2 receptor partial agonist (aripiprazole) and a dopamine D2 receptor antagonist (amisulpride) on glutamatergic metabolites in the anterior cingulate cortex (ACC), striatum and thalamus in healthy controls.

A double-blind, within-subject, cross-over, placebo-controlled study design with two arms (n = 25 per arm) was conducted. Healthy volunteers received either aripiprazole (up to 10 mg/day) for 7 days or amisulpride (up to 400 mg/day) and a corresponding period of placebo treatment in a pseudo-randomised order. Magnetic resonance spectroscopy (1H-MRS) was used to measure glutamatergic metabolite levels and was carried out at three different time points: baseline, after 1 week of drug and after 1 week of placebo. Values were analysed as a combined measure across the ACC, striatum and thalamus.

Aripiprazole significantly increased glutamate + glutamine (Glx) levels compared with placebo (β = 0.55, 95% CI [0.15, 0.95], P = 0.007). At baseline, the mean Glx level was 8.14 institutional units (s.d. = 2.15); following aripiprazole treatment, the mean Glx level was 8.16 institutional units (s.d. = 2.40) compared with 7.61 institutional units (s.d. = 2.36) for placebo. This effect remained significant after adjusting for plasma parent and active metabolite drug levels. There was an observed increase with amisulpride that did not reach statistical significance.

One week of aripiprazole administration in healthy participants altered brain Glx levels as compared with placebo administration. These findings provide novel insights into the relationship between antipsychotic treatment and brain metabolites in a healthy participant cohort.

Cerebral glutamate and gamma-aminobutyric acid (GABA) levels might predict clinical outcome in individuals at ultrahigh risk (UHR) for psychosis but have previously primarily been investigated in smaller cohorts. We aimed to study whether baseline levels of glutamate and GABA in anterior cingulate cortex (ACC) and glutamate in thalamus could predict remission status and whether baseline metabolites differed in the remission versus the nonremission group. We also investigated the relationship between baseline metabolite levels and severity of clinical symptoms, functional outcome, and cognitive deficits at follow-up.

About 124 UHR individuals were recruited at baseline. In this, 74 UHR individuals were clinically and cognitively assessed after 12 months, while remission status was available for 81 (25 remission/56 nonremission). Glutamate and GABA levels were assessed at baseline using 3 T proton magnetic resonance spectroscopy. Psychopathology, symptom severity, and remission were assessed with the Comprehensive Assessment of At-Risk Mental States and Clinical Global Impression and functional outcome with the Social and Occupational Functioning Assessment Scale. Cognitive function was estimated with the Cambridge Neuropsychological Test Automated Battery.

There were no differences between baseline glutamate and GABA levels in subjects in the nonremission group compared with the remission group, and baseline metabolites could not predict remission status. However, higher baseline levels of GABA in ACC were associated with clinical global improvement (r = −0.34, N = 51, p = 0.01) in an explorative analysis.

The variety in findings across studies suggests a probable multifactorial influence on clinical outcome in UHR individuals. Future studies should combine multimodal approaches to attempt prediction of long-term outcome.