- Higher baseline amygdala D2/3 receptor availability associates with lower fear-related connectivity between right amygdala and right anterior insula.
- Greater differential SCR (CS+ versus CS-) links to reduced functional connectivity between right amygdala and left anterior insula.
- Lower dorsal striatal D2/3 availability predicts greater mean SCRs to US omission and shows no association with extinction-related reductions.
Neuroimage Rep. 2026 Sep 4;6(4):100402. doi: 10.1016/j.ynirp.2026.100402. eCollection 2026 Dec.
ABSTRACT
BACKGROUND: The ability to learn what is dangerous in the environment and what no longer exerts a threat is essential for survival. The latter process is studied using Pavlovian fear extinction, the repeated presentation of a feared stimulus that gradually attenuates the fear response. Dysregulation of the extinction process is implicated in a range of anxiety disorders, yet the neurobiological mechanisms supporting extinction learning in humans remain incompletely mapped, particularly with respect to the modulating role of dopamine.
OBJECTIVE: To examine the role of baseline dopamine D2/3 receptors in fear extinction and responses to unconditioned stimulus (US) omission.
MATERIALS AND METHODS: Fifteen healthy adults completed a differential cued Pavlovian conditioning paradigm, including one conditioned stimulus (CS+) paired with an aversive electric shock US and one never paired (CS-). Participants underwent [11C]raclopride positron emission tomography (PET) of baseline dopamine D2/3 receptor availability prior to fear acquisition, and subsequent fear extinction with skin conductance response (SCR) and functional magnetic resonance imaging (fMRI) continuously recorded.
RESULTS: SCR and neural activations indicated remaining conditioned responding during extinction, with greater responses to CS+ than to CS- in the insula and frontoparietal regions. Higher baseline dopamine D2/3 receptor availability in the amygdala was associated with lower fear-related (CS+> CS-) connectivity between the right amygdala and the right anterior insula. Higher differential SCR (CS+> CS-) was associated with reduced functional connectivity between the right amygdala and left anterior insula. Lower baseline dorsal striatal D2/3 receptor availability was associated with greater mean SCRs to US omission. No associations were detected between baseline D2/3 receptor availability and extinction-related reductions of conditioned SCR or neural responses across trials.
CONCLUSION: These findings suggest that individual differences in dopamine D2/3 receptor availability are related to threat processing and responses to US omission, but may be less strongly associated with extinction learning itself.
PMID:42733917 | PMC:PMC13571913 | DOI:10.1016/j.ynirp.2026.100402
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