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Mental models in medial prefrontal cortex: cognitive maps and prospection

Representation of spatial position appears to coordinate associative memories in the rodent anterior cingulate cortex. These can spontaneously re-activated to recall multimodal features of remote reward locations. This may be navigation of a ‘cognitive map’ that could serve as a useful model to study prospection and other cognitive phenomena associated with medial prefrontal cortex.

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Hierarchical reinforcement learning inspired by the brain

The brain represents space at several spatial scales. Hierarchical reinforcement learning based on such a schema of abstraction is faster to adapt, and more computationally efficient, than RL at a single level of abstraction. It also provides a simple method of knowledge transfer. We are currently investigating how non-spatial information may be similarly abstracted.

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Neural basis of win-stay and lose-shift responding (rats)

Animals have a strong tendency to repeat choices that were previously rewarded (win-stay) and to shift choice away from choices immediately after reward omission (lose-shift). In a series of papers, we found that lose-shift is a reflexive choice strategy dependent on the lateral striatum, whereas win-stay is learned and depends on the ventral striatum.

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Neural basis of win-stay and lose-shift responding (humans)

Human adults inappropriately use a lose-shift strategy when they are concurrently performing a cognitively demanding task. This suggests that executive processing normally suppresses lose-shift responses that are presumably mediated by striatum, as in rats. Children aged 5-9 show lose-shift responding in the absence of a demanding task, but this is diminished in older children. We suggest this is due to the development of the prefrontal cortex. The presumed competition between executive and striatal systems is different in men and women, and strongly modulated by the self-reported use of alcohol and marijuana by subjects (in preparation).

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Alteration of brain function by abused drugs, stress, and other risk factors for mental illness

Dysfunction of the prefrontal cortex, striatum, and hippocampus present in addiction and several other mental illnesses. We are experimentally testing the theory that stress and/or drug abuse induce a functional simplification of these networks, which impairs the brain’s ability to represent and update a mental model of the world. This impairs information processing in the circuit, and promotes characteristic symptoms, such as mood dysregulation, attention dysregulation, and perseveration in poor response strategies.

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