Temporal dynamics of basal ganglia under-recruitment in Parkinson's disease : transient caudate abnormalities during updating of working memory

• Using hybrid-blocked/event-related fMRI and the 2-back taskwe aimed to decompose tonic and phasic temporal dynamics ofbasal ganglia response abnormalities in working memory associatedwith early untreated Parkinson's disease. In view of the tonic/phasicdopamine hypothesis, which posits a functional division betweenphasic D2-dependent striatal updating processes and tonic D1-dependentprefrontal context-maintenance processes, we predicted thatnewly diagnosed, drug-naïve Parkinson's disease patients,with selective striatal dopamine deprivation, would demonstratetransient rather than sustained activation changes in the basalganglia during 2-back performance. Task-related activation patternswithin discrete basal ganglia structures were directly comparedbetween patients and healthy elderly controls. The obtainedresults yielded uniquely transient underactivation foci in caudatenuclei, putamen and globus pallidus in Parkinson's disease patients,which indicates suboptimal phasic implementation of striatalD2-dependent gating mechanisms during updating. Sustained underactivationwas only seen in the anterior putamen, which may reflect initialsigns of tonic control impairment. No significant changes wereexhibited in prefrontal cortex. The present findings resonatewell with the tonic/phasic dopamine account and suggest thatbasal ganglia under-recruitment associated with executive dysfunctionin early Parkinson's disease might predominantly stem from deficienciesin phasic executive components subserved by striatum.

Subject headings

SAMHÄLLSVETENSKAP  -- Psykologi (hsv//swe)

SOCIAL SCIENCES  -- Psychology (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Neurologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Neurology (hsv//eng)

Keyword

Parkinson's disease

hybrid fMRI

cognitive control dynamics

verbal working memory

Striatum

Psychology

psykologi

Publication and Content Type

ref (subject category)

art (subject category)