L. Godbout et J. Doyon, Defective representation of knowledge in Parkinson's disease: Evidence from a script-production task, BRAIN COGN, 44(3), 2000, pp. 490-510
The deficits seen in frontal-lobe patients and in the elderly show clearly
that spontaneous script generation depends on good frontal-lobe function. S
hallice, however, has proposed that one aspect of script generation (conten
tion scheduling, CS) which is involved in the activation and maintenance of
overlearned or routine scripts may depend more on the basal ganglia. Patie
nts with Parkinson's disease would thus be expected to manifest deficits so
mewhat different from those observed in frontal-lobe patients when generati
ng scripts. The performances of 16 nondemented and nondepressed patients wi
th idiopathic Parkinson's disease were compared to those of 16 age-matched
normal control subjects under two experimental conditions; routine, forward
script generation and nonroutine, backward script generation. Parkinsonian
patients generated scripts significantly deprived of contextual elements i
n the forward condition and made significantly more sequencing and persever
ative errors in both forward and backward conditions than did normal subjec
ts. They also produced a significantly higher number of irrelevant intrusio
ns, in both conditions, than did controls. These results support, in a gene
ral sense, Shallice's notion that the basal ganglia are important in script
generation; however, other specific predictions of Shallice's model were n
ot supported by our findings. (C) 2000 Academic Press.