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The aim is to identify neural correlates of impulsivity related to reward expectancy, and how they differentiate between bipolar disorder and externalizing disorders.

March 21, 2026Molecular Psychiatry0 citationsOpen Access

Elevated pre-supplementary motor area activity during reward expectancy: An impulsivity-related neural marker of vulnerability to bipolar and externalizing disorders

RRRobert RaederUniversity of Pittsburgh MAManan AroraUniversity of Pittsburgh MBMichele A. BertocciUniversity of Pittsburgh

Key Points

The aim is to identify neural correlates of impulsivity related to reward expectancy, and how they differentiate between bipolar disorder and externalizing disorders.
Two independent samples aged 18–30 were analyzed, including individuals with externalizing disorders and a euthymic BD group.
Impulsivity was assessed using the Behavioral Activation System and UPPS-P scales.
Whole-brain regressions were used to identify neural correlates during reward expectancy trials.
ANCOVA was employed to compare neural activity among distinct impulsivity tertile groups.
A positive association was found between BAS Fun Seeking and pre-supplementary motor area (pre-SMA) activity, significant in both discovery and replication phases.
A pre-SMA × depression interaction indicated that depressive symptoms moderated the BAS Fun Seeking and pre-SMA activity correlation.
High Fun Seeking and externalizing disorder groups showed greater pre-SMA activity compared to low Fun Seeking, especially since individuals on benzodiazepines were excluded.

Abstract

Abstract Mania/hypomania is pathognomonic of bipolar disorder (BD), yet early identification remains challenging. Impulsivity is a key feature of mania/hypomania and of externalizing disorders that may predispose to BD, but neural markers of impulsivity-related risk remain unknown. This study aimed to identify reward expectancy (RE)-related neural correlates of impulsivity facets, test moderation by current affective/anxiety symptoms, and determine whether such markers differentiate BD and/or externalizing disorders from low impulsivity individuals. Two independent BD-risk samples aged 18–30 years, including individuals with prior externalizing disorder diagnoses but not BD, were recruited; a euthymic BD group was also recruited. Impulsivity facets were assessed via Behavioral Activation System (BAS) and UPPS-P scales. Whole-brain regressions identified neural correlates of impulsivity facets during RE. Linear models tested replication and current affective/anxiety symptom moderation. ANCOVA compared neural activity among BD, externalizing, and non-BD/externalizing impulsivity tertile groups. Whole-brain regressions revealed a positive association between BAS Fun Seeking and pre-supplementary motor area (pre-SMA) activity ( p FWE = 0.003, k = 167), which replicated when depressive symptoms were covaried (discovery: β = 2.73, p < 0.001; replication: β = 0.88, p = 0.036; combined: β = 1.49, p < 0.001). A significant pre-SMA × depression interaction ( β = –0.08, p = 0.037) indicated depressive symptoms attenuated the pre-SMA-Fun Seeking association. Group comparisons revealed greater pre-SMA activity in high-Fun Seeking ( p < 0.001) and externalizing disorder groups ( p = 0.039) versus low-Fun Seeking, with similar trends observed in BD once individuals taking medications, particularly benzodiazepines ( p = 0.012), were excluded. Pre-SMA hyperactivity during RE is a robust neural correlate of BAS Fun Seeking, moderated by depression severity. This pattern represents a trait-linked neural marker of impulsivity associated with vulnerability to BD and externalizing disorders, informing early risk identification and intervention.

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