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  Optimal helplessness: a normative framework for depression

Huys, Q., & Dayan, P. (2006). Optimal helplessness: a normative framework for depression. Poster presented at Fifteenth Annual Computational Neuroscience Meeting (CNS*2006), Edinburgh, UK.

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Huys, Q, Author
Dayan, P1, Author              
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 Abstract: Depression is a hugely debilitating disease afflicting millions of people. As for most psychiatrical conditions, it is hard to characterize precisely the set of underlying neural problems, except to say that neuromodulatory systems, notably dopamine, serotonin and norepinephrine, all seem to play key roles, based on pharmacotherapy and a variety of more or less valid animal models. Surprisingly, the recent wealth of accounts of the role of these very neuromodulators in the sort of normal cognitive functions that are disrupted in depression, schizophrenia and the like, have yet to be fully informed by (or indeed themselves to inform) the characteristics of the psychiatric conditions. Depression, and particularly the simpler popular animal models of the disorder such as learned helplessness (LH, and ch ronic mild stress (CMS), suggest two gross features of neuromodulatory systems that have not hitherto attracted much attention. The one we consider here is neuromodulatory metaplasticity, the notion that there are different gross states of adaptation (which we call attitudes) of neuromodulatory responsivity. Depression has been characterized in terms of affective blunting, reducing the import of not only rewards, but punishments too. We consider this a normative allostatic adaptation to a particular structure of environmental rewards and punishments. Whether the transition into this attitude from a normal attitude is occasioned merely by the statistics of rewards and punishments (in a more Pavlovian manner) or as an optimal internally-directed 'action' (in a more instrumental control strategy) is presently unclear. The second feature of neuromodulation is rich dynamical feedback interactions between the different systems, as suggested by both the natural history of disorders and the timecourse of action of drugs. These interactions will exert significant influence over the transition into a depressed attitude, and the apparently maladaptive persistence of this attitude in depressed patients. Unfortunately, since the major animal models do not exhibit the persistence, it is hard to get even qualitative constraints on this process. Here, we focus on neuromodulatory metaplasticity, characterizing the depressed attitude engendered by LH and CMS in normative terms as an appropriate response to statistics of reward and punishment. We show that these paradigms induce conditions under which the optimal strategy is a form of extreme self-preservation, and in which, therefore, the actual values of rewards and punishments are severely blunted. We start by describing the models; then develop our normative model, and finally draw some broader conclusions.

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 Dates: 2006-07
 Publication Status: Published online
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Title: Fifteenth Annual Computational Neuroscience Meeting (CNS*2006)
Place of Event: Edinburgh, UK
Start-/End Date: 2006-07-15 - 2006-07-18

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Title: Fifteenth Annual Computational Neuroscience Meeting (CNS*2006)
Source Genre: Proceedings
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Pages: - Volume / Issue: - Sequence Number: S88 Start / End Page: 59 Identifier: -