Balancing Memory Systems: A Stress-Induced Shift from Contextual to Stimulus-Response Memory and the Role of Dopamine
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2022-12-19
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en
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Abstract
Stress is thought to induce a shift from a more controlled and rational action mode, to a more
habitual and automatic action mode. This is particularly the case for memory: under stress,
memory seems to rely less on previously learned context, and more on habits, often measured
as low-level stimulus-response associations. However, the neural mechanism by which this
shift occurs remains unclear. Context memory is thought to rely more on prefrontal and
hippocampal regions, while stimulus-response memory is thought to recruit the striatum. The
present study investigated the effect of stress on contextual memory and stimulus-response
memory at the behavioral and neural level and aimed at establishing the underlying neural
mechanisms and the contribution of dopamine to stress-driven changes. In a between-subject
design, participants underwent a control or stress procedure and a pharmacological or placebo
manipulation. Subsequently, participants performed a visual search task developed to
discriminate between the two memory systems. We hypothesized that 1) stress would induce
the expected shift from context memory to stimulus-response memory, 2) that this would be
reflected by a neural shift from prefrontal-hippocampal activity to striatal activity, 3) and that
this effect would be neutralized, both neurally and behaviorally, by dopamine depletion. In my
thesis, I empirically tested the first two hypotheses on a subset of available data. As inclusion
is ongoing and the study follows a double-blind procedure, data from drug effects are currently
not available. Behaviorally, the results showed that the paradigm supports context memory but
less clear stimulus-response memory. We observed some indications of stress-induced context
memory impairment as suggested by previous research. Neurally, we observed a generalized
effect of stress, with increased activity across prefrontal, hippocampal, and striatal regions.
Some indication was found that under stress activity was increased for stimulus-response and
decreased for context memory, although without evidence for the expected regional specificity.
Finally, I speculated on the expected results of the dopaminergic manipulation, reflecting on
the implication for future research.
Keywords: stimulus-response memory, context memory, stress, dopamine, hippocampal and
striatal memory
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Faculteit der Sociale Wetenschappen