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Ahmed Mustafa"A Connectionist Model of Cognitive Performance in Parkinson's patients"

Abstract :

Most existing models of dopamine and learning in Parkinson’s disease
(PD) focus on simulating the role of basal ganglia dopamine in reinforcement learning. Much data argue, however, for a critical role for prefrontal cortex (PFC) dopamine in stimulus selection in attentional learning. Here, we present a new computational model that simulates performance category learning and reversal tasks. The model addresses how PD and dopamine medications affect stimulus selection processes, which mediate reinforcement learning. In this model, PFC dopamine is key for attentional learning, while basal ganglia dopamine, consistent with other models, is key for reinforcement and motor learning. The model assumes that competitive dynamics among PFC neurons is the neural mechanism underlying stimulus selection with limited attentional resources, whereas competitive dynamics among striatal neurons is the neural mechanism underlying action selection. According to our model, PD is associated with decreased phasic and tonic dopamine levels in both the PFC and basal ganglia. We argue that dopamine medications increase dopamine levels in both the basal ganglia and PFC, which, in turn, increase tonic dopamine levels but decrease the magnitude of phasic dopamine signaling in these brain structures. Here, we show how model accounts for various neuropsychological data.

Invitation de Thomas Boraud


Selected publications

A neurocomputational model of classical conditioning phenomena: a putative role for the hippocampal region in associative learning.Moustafa AA, Myers CE, Gluck MA.Brain Res. 2009 Jun 18;1276:180-95. Epub 2009 Apr 18.

A role for dopamine in temporal decision making and reward maximization in parkinsonism. Moustafa AA, Cohen MX, Sherman SJ, Frank MJ.J Neurosci. 2008 Nov 19;28(47):12294-304.

A dopaminergic basis for working memory, learning and attentional shifting in Parkinsonism.Moustafa AA, Sherman SJ, Frank MJ.Neuropsychologia. 2008 Nov;46(13):3144-56. Epub 2008 Jul 19.

Hold your horses: impulsivity, deep brain stimulation, and medication in parkinsonism.Frank MJ, Samanta J, Moustafa AA, Sherman SJ.Science. 2007 Nov 23;318(5854):1309-12. Epub 2007 Oct 25.     

Genetic triple dissociation reveals multiple roles for dopamine in reinforcement learning.Frank MJ, Moustafa AA, Haughey HM, Curran T, Hutchison KE.Proc Natl Acad Sci U S A. 2007 Oct 9;104(41):16311-6. Epub 2007 Oct 3.