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Thomas E. Hazy
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Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2013) 25 (6): 843–851.
Published: 01 June 2013
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We can learn from the wisdom of others to maximize success. However, it is unclear how humans take advice to flexibly adapt behavior. On the basis of data from neuroanatomy, neurophysiology, and neuroimaging, a biologically plausible model is developed to illustrate the neural mechanisms of learning from instructions. The model consists of two complementary learning pathways. The slow-learning parietal pathway carries out simple or habitual stimulus–response (S-R) mappings, whereas the fast-learning hippocampal pathway implements novel S-R rules. Specifically, the hippocampus can rapidly encode arbitrary S-R associations, and stimulus-cued responses are later recalled into the basal ganglia-gated pFC to bias response selection in the premotor and motor cortices. The interactions between the two model learning pathways explain how instructions can override habits and how automaticity can be achieved through motor consolidation.
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2012) 24 (2): 351–366.
Published: 01 February 2012
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Appetitive goal-directed behavior can be associated with a cue-triggered expectancy that it will lead to a particular reward, a process thought to depend on the OFC and basolateral amygdala complex. We developed a biologically informed neural network model of this system to investigate the separable and complementary roles of these areas as the main components of a flexible expectancy system. These areas of interest are part of a neural network with additional subcortical areas, including the central nucleus of amygdala, ventral (limbic) and dorsomedial (associative) striatum. Our simulations are consistent with the view that the amygdala maintains Pavlovian associations through incremental updating of synaptic strength and that the OFC supports flexibility by maintaining an activation-based working memory of the recent reward history. Our model provides a mechanistic explanation for electrophysiological evidence that cue-related firing in OFC neurons is nonselectively early after a contingency change and why this nonselective firing is critical for promoting plasticity in the amygdala. This ambiguous activation results from the simultaneous maintenance of recent outcomes and obsolete Pavlovian contingencies in working memory. Furthermore, at the beginning of reversal, the OFC is critical for supporting responses that are no longer inappropriate. This result is inconsistent with an exclusive inhibitory account of OFC function.
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2011) 23 (11): 3598–3619.
Published: 01 November 2011
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A paradigmatic test of executive control, the n -back task, is known to recruit a widely distributed parietal, frontal, and striatal “executive network,” and is thought to require an equally wide array of executive functions. The mapping of functions onto substrates in such a complex task presents a significant challenge to any theoretical framework for executive control. To address this challenge, we developed a biologically constrained model of the n -back task that emergently develops the ability to appropriately gate, bind, and maintain information in working memory in the course of learning to perform the task. Furthermore, the model is sensitive to proactive interference in ways that match findings from neuroimaging and shows a U-shaped performance curve after manipulation of prefrontal dopaminergic mechanisms similar to that observed in studies of genetic polymorphisms and pharmacological manipulations. Our model represents a formal computational link between anatomical, functional neuroimaging, genetic, behavioral, and theoretical levels of analysis in the study of executive control. In addition, the model specifies one way in which the pFC, BG, parietal, and sensory cortices may learn to cooperate and give rise to executive control.