Impairment of the supervisory attentional system in early untreated patients with Parkinson's disease

The aim of this study was to specify the frontal type dysfunction widely re ported in Parkinson's disease (PD) early in the course of the disease and b efore dopaminergic therapy. Seventeen "de novo" PD patients and 17 healthy control subjects performed modified versions of the Stroop word-color test and the Brown Peterson paradigm. A dissociation between results on the two tasks was observed in PD patients. They had difficulties in inhibiting a st rong habitual response and establishing a new, better adapted pattern of re sponse; but they performed as well as controls in a dual-task paradigm requ iring correct allocation of the processing resources of working memory. Ear ly in the course of the disease, untreated PD patients suffer from dysfunct ion of the supervisory attentional system. However, the present findings su ggest that this system is not a single unit but rather could be composed of multiple subsystems whose sensitivity depends on the origin of frontal dys function. Indeed, only a few of these subsystems seemed to be impaired in d e novo PD patients. It can be hypothesized that those involved in the pheno mena of adaptation and consolidation of currently appropriate responses dep end on the dorsolateral prefrontal loop, which is affected by the dopaminer gic innervation of the caudate nucleus.