Is impaired memory for spatial location in Parkinson's disease domain specific or dependent on 'strategic' processes?

Spatial memory has been found to be impaired in Parkinson's disease (PD). To determine the nature of the deficit, we compared the performance of'standard' levodopa-treated patients with PD to that of matched control subjects in different situations: (i) spatial versus verbal conditional associative learning; (ii) 'global' versus 'local' contextual encoding; (iii) pattern span and related supraspan learning. The relationship between dopaminergic depletion, which characterizes the disease, and the impaired memory processes was investigated by comparing the performance of 'de novo' not yet treated PD patients to that of matched control subjects. Both groups of PD patients were impaired in all situations requiring strategic processes, shared a decreased pattern span and had a normal visuospatial learning once the pattern span was taken into account. All these results suggest that the memory deficit for spatial location observed in PD results mainly from a disturbance of strategic processes and from decreased attentional resources, which may be due, at least in part, to the dopaminergic depletion and related striatofrontal dysfunction.