Dopaminergic modulation of stress-induced alterations in goal-directed
behaviour and associated brain activation
Abstract
Background and purpose: Being exposed to acute stress may cause people
to behave more habitual, which purportedly is associated stress-induced
increased dopamine release. In contrast, experimental rises in systemic
dopamine levels have been shown to increase goal-directed behaviour and,
thus, decrease habitual control. Whether experimentally increased
dopamine functioning can modulate stress-induced reductions in
goal-directed behaviour and its neural substrates, is currently unknown.
Experimental approach: To assess whether increased dopamine functioning
reduces stress effects on goal-directed behaviour, 100 participants were
recruited who were randomly assigned to one of four conditions in a 2x2
between participants design. Participants underwent a stress induction
protocol (Maastricht Acute Stress Test; MAST) or a control procedure and
received methylphenidate (40 mg, oral) or placebo. In a well-established
instrumental learning paradigm, participants were trained to learn
stimulus-response-outcome associations, after which rewards were
selectively devalued and participants’ goal-directed behaviour was
assessed at peak cortisol/methylphenidate concentrations in a magnetic
resonance imaging scanner to assess brain activation. Key results: The
MAST effectively increased physiological measures of stress (salivary
cortisol, blood pressure) and subjective stress. Methylphenidate also
increased cortisol levels over time. While stress selectively reduced
goal-directed behaviour, this effect was not modulated by
methylphenidate. However, methylphenidate modulated stress effects on
activation in paracingulate, orbitofrontal cortex, and anterior
cingulate associated with expected value representation in goal-directed
behaviour. Conclusion and implications: Our neuroimaging data suggest
increased dopamine levels reverse stress-induced changes in brain
activation associated with goal-directed behaviour. These effects may be
relevant for preventing stress-induced relapse in addictive behaviour.