Implicit task sequence learning in patients with Parkinson's disease, frontal lesions and amnesia: the critical role of fronto–striatal loops.
The purpose of this study was to investigate the role of the fronto–striatal system for implicit task sequence learning. We tested performance of patients with compromised functioning of the fronto–striatal loops, that is, patients with Parkinson's disease and patients with lesions in the ventromedial or dorsolateral prefrontal cortex. We also tested amnesic patients with lesions either to the basal forebrain/orbitofrontal cortex or to thalamic/medio-temporal regions. We used a task sequence learning paradigm involving the presentation of a sequence of categorical binary-choice decision tasks. After several blocks of training, the sequence, hidden in the order of tasks, was replaced by a pseudo-random sequence. Learning (i.e., sensitivity to the ordering) was assessed by measuring whether this change disrupted performance. Although all the patients were able to perform the decision tasks quite easily, those with lesions to the fronto–striatal loops (i.e., patients with Parkinson's disease, with lesions in the ventromedial or dorsolateral prefrontal cortex and those amnesic patients with lesions to the basal forebrain/orbitofrontal cortex) did not show any evidence of implicit task sequence learning. In contrast, those amnesic patients with lesions to thalamic/medio-temporal regions showed intact sequence learning. Together, these results indicate that the integrity of the fronto–striatal system is a prerequisite for implicit task sequence learning.
Beat
B
Meier
Brigitte
B
Weiermann
Klemens
K
Gutbrod
Marianne A
MA
Stephan
Josephine
J
Cock
René M
RM
Mür
Alain
A
Kaelin-Lang
D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D003704:Dementia / Q000209:etiology*; D005260:Female; D005625:Frontal Lobe / Q000473:pathology*; D006801:Humans; D007859:Learning Disabilities / Q000209:etiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications* / Q000473:pathology* / Q000523:psychology; D011930:Reaction Time / Q000502:physiology; D012691:Serial Learning / Q000502:physiology*