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Behavioral/Systems/Cognitive Increased Dependence of Action Selection on Recent Motor
 

Summary: Behavioral/Systems/Cognitive
Increased Dependence of Action Selection on Recent Motor
History in Parkinson's Disease
Rick C. Helmich,1,3 Esther Aarts,1,2 Floris P. de Lange,1 Bastiaan R. Bloem,3 and Ivan Toni1,2
Centres for 1Cognitive Neuroimaging and 2Cognition, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, and
3Department of Neurology and Parkinson Centre Nijmegen (ParC), Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands
It is well known that the basal ganglia are involved in switching between movement sequences. Here we test the hypothesis that this
contribution is an instance of a more general role of the basal ganglia in selecting actions that deviate from the context defined by the
recent motor history, even when there is no sequential structure to learn or implement. We investigated the effect of striatal dopamine
depletion [in Parkinson's disease (PD)] on the ability to switch between independent action plans. PD patients with markedly lateralized
signsperformedahandlateralityjudgmenttaskthatinvolvedactionselectionoftheirmostandleastaffectedhand.Trialswherepatients
selectedthesame(repeat)orthealternative(switch)handasinaprevioustrialwerecompared,andthiswasdoneseparatelyforthemost
and least affected hand. Behaviorally, PD patients showed switch-costs that were specific to the most affected hand and that increased
with disease severity. Functional magnetic resonance imaging (fMRI) showed that this behavioral effect was related to the state of the
frontostriatal system: as disease severity increased, contributions of the basal ganglia to the selection process and their effective connec-
tivity with the medial frontal cortex (MFC) decreased, whereas involvement of the MFC increased. We conclude that the basal ganglia are
important for rapidly switching toward novel motor plans even when there is no sequential structure to learn or implement. The
enhanced MFC activity may result either from reduced focusing abilities of the basal ganglia or from compensatory processes.
Introduction
The basal ganglia (BG) are important for set-shifting (Cools et al.,

  

Source: Aarts, Esther - Helen Wills Neuroscience Institute, University of California at Berkeley

 

Collections: Biology and Medicine