University of Cambridge > > Zangwill Club > "Bonsai trees in your head: the powerful influence of reflexive processes on goal-directed decision-making".

"Bonsai trees in your head: the powerful influence of reflexive processes on goal-directed decision-making".

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Decision-making in the real world is tricky, because the decisions we make now affect future choices, and future choices and outcomes should guide current decisions. The exponentially increasing number of combinations of future choices and actions means that brute-force approaches to sequential decision-making only work for trivially small problems. Using a computational modelling approach to analyse responses on a deterministic sequential decision-making task, we demonstrate a novel and powerful influence on goal-directed decision-making in humans, “pruning”, a simple reflexive process that cuts down (or prunes) an expanding decision tree to a computationally manageable size. Pruning involves automatically discounting sequences of decisions that feature large negative outcomes, no matter what the overall outcome; it is different to loss aversion. Our participants used this pruning strategy even when it was disadvantageous, and the tendency to prune was related to mild depressive symptoms. In a follow-up neuroimaging study we replicated this behavioural pattern, and found that pruning was associated with responses in the subgenual anterior cingulate cortex and periaqueductal grey, which are implicated in mood and anxiety disorders. Finally, initial psychopharmacological evidence supports the hypothesis that pruning is influenced by serotonin signalling. We interpret these findings within a theoretical framework that relates Pavlovian behavioural inhibition to serotonin and mood disorders.

Biography: Jonathan Roiser

Jonathan Roiser studied Natural Sciences at Trinity College, Cambridge, as an undergraduate and remained there for his doctorate in the Department of Psychiatry. His PhD examined the effects of monoamine depletions on mood and cognitive performance, with a particular emphasis on demonstrating that genetic variation can explain some of the inter-subject variability in response to perturbations of the serotonin system. He then spent a year conducting a pharmacological fMRI study at the National Institute of Mental Health (NIMH), USA , the results of which suggested a potentially important role for the habenula in depression, a focus of his current research.

Following a post-doctoral appointment at the UCL Institute of Neurology, London, where he investigated the neural mechanisms underpinning psychotic phenomena and cognitive impairment in schizophrenia, he was appointed to a faculty post at the UCL Institute of Cognitive Neuroscience where he is currently Reader (Associate Professor) in cognitive neuroscience. He has published over 50 articles, with an h-index of 21, and his work has been funded by the British Academy and Medical Research Council. In 2008 he founded the UCL -NIMH Joint Doctoral Training Program in Neuroscience, which he co-directs. His research aims to understand the neurobiological basis of psychiatric symptoms, combining behavioural, psychopharmacological and genetic approaches with neuroimaging techniques and computational analysis. In the future he hopes to further understand the sources of individual differences in response to different therapeutic approaches in depression, with the ultimate goal of realising the potential for using neuroscience to inform treatment strategies in mental health

This talk is part of the Zangwill Club series.

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