Learning under threat: threat-induced freezing and the adaptation to environmental volatility
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2022-09-05
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en
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Threat occurs often in unpredictable volatile situations. Adequate coping with acute threat requires one to flexibly adapt to environmental volatility. While stable environments require a low learning rate, rapidly changing volatile environments require a high learning rate. Although there is increasing knowledge from computational neuroscience on how our brains enable learning rate adaptation, it remains unclear how psychophysiological changes during acute threat affect this skill. Recent empirical and theoretical work proposed that the bradycardia and immobility observed during threat-induced freezing enhance perceptual sensitivity, subjective value integration, and action preparation. However, it is still unknown whether stronger freezing responses are also linked to stronger adaptation of learning rate to environmental volatility. The aim of the current thesis is to test this hypothesis, and to explore the neural correlates of such a potential effect. Fifty-two participants (22 females) performed a probabilistic reversal learning task featuring a stable and a volatile cue inside a magnetic resonance imaging scanner. The task entailed a go/no-go type of shooting simulation where errors were reinforced by a shock, during which participants found out through trial and error which target to shoot and not to shoot. Freezing was qualified by significant threat-anticipatory heart rate deceleration. Our findings showed that in the volatile condition participants froze more and made more errors. A Pearce-Hall learning model featuring a flexible learning rate fitted the participants’ behavioural data best. Learning rates were higher for volatile cues, and trial-wise freezing was positively associated with trial-wise learning rate across cues. These effects are in line with our hypothesis that threat- induced freezing may facilitate the adaptation of learning to volatile environments. As far as neural correlates go, the dorsal anterior cingulate cortex was more active for volatile than stable cues in the feedback phase of the task, but not during the pre-decision phase. I will end by discussing additional neuroimaging analyses that should be performed to further explore the neural underpinnings of the effect of freezing on learning.
Keywords: freezing, learning, volatility, decision-making, threat, dACC
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Faculteit der Sociale Wetenschappen