Relationships between striatal dopamine denervation and frontal executive tests in Parkinson's disease

Indirect evidence from human and monkey investigations supports the idea th at impaired frontal tasks in Parkinson's disease (PD) may result from stria to-frontal disruption caused by dopamine (DA) denervation of the caudate nu cleus. To directly investigate this hypothesis, we used PET with C-11-S-Nom ifensine (C-11-S-NMF), a sensitive marker of striatal DA denervation, in 10 non-demented PD patients in whom two frontal executive tests, the object a lternation (OA) and the conditional associative learning (CAL) tasks, thoug ht to reflect mainly set-shifting/inhibition and planning, respectively, we re given. In addition, the central executive function of verbal working mem ory was assessed with the Brown Peterson paradigm (BPP). We found a highly significant correlation between right caudate C-11-S-NMF specific binding a nd OA performance, less significant and reverse-direction correlations betw een CAL performance and putamen C-11-S-NMF binding, and no significant corr elation with BPP performance. Thus, caudate DA denervation may subtend poor set-shifting/inhibition process in PD. Our results also point to distinct and complex relationships between striatal DA and specific frontal tasks. ( C) 1999 Elsevier Science Ireland Ltd. All rights reserved.