Dopaminergic Mechanisms Underlying Normal Variation in Trait Anxiety

Area of Science:

• Neuroscience
• Psychiatry
• Neuroimaging

Background:

• Trait anxiety is linked to altered activity in corticolimbic pathways (amygdala and rostral anterior cingulate cortex).
• Individual differences in dopamine neurochemistry's relation to anxiety and corticolimbic circuit activity are poorly understood.
• The popular concept of a

Purpose of the Study:

• To investigate the relationship between individual differences in dopamine release, functional connectivity, and trait anxiety in healthy adults.
• To examine dopamine release in the amygdala and rostral anterior cingulate cortex (rACC) using [11C]raclopride positron emission tomography (PET).
• To assess functional connectivity between the amygdala and rACC using resting-state functional magnetic resonance imaging (fMRI).

Main Methods:

• Collected [11C]raclopride PET scans twice per participant to measure endogenous dopamine release.
• Administered methylphenidate to block dopamine transporters and assess dopamine release via competitive displacement.
• Utilized resting-state fMRI to measure functional connectivity between the amygdala and rACC.
• Measured trait anxiety using self-report questionnaires in healthy adult males and females.

Main Results:

• Individuals with higher dopamine release in the amygdala and rACC reported lower trait anxiety.
• Lower trait anxiety was associated with reduced functional connectivity between the rACC and amygdala.
• A modest negative relationship was observed between functional connectivity and dopamine release, with reduced connectivity accompanying higher dopamine release.

Conclusions:

• Findings contribute to hypodopaminergic models of anxiety.
• Support the utility of combining fMRI and PET for understanding neurochemical function in affective processes.
• Suggest that higher trait anxiety in healthy adults may be partly due to reduced dopamine neurotransmission.