Neuropsychological correlates of prospective memory: A comparison between tremor-dominant Parkinson's disease and cervical dystonia.

Cervical Dystonia (CD) and Parkinson's disease, particularly tremor-dominant motor phenotype (TD-PD), showed a selective deficit of time-based prospective memory (TBPM). The two movement disorders are mainly characterized by dysfunctions of basal-ganglia and prefrontal cortex but it is reported that cerebellum also plays a key role in their pathogenesis. These cerebral structures are specifically involved in TBPM rather than in event-based PM (EBPM), but until now no study directly compared these two components of PM between CD and TD-PD patients. Therefore, the present study aimed at investigating if differences in PM functioning between CD and TD-PD patients might exist and if the type of movement disorder moderated the relationship between deficit of PM and deficit of executive functions and retrospective memory. Thirty TD-PD, 27CD patients and 29 healthy subjects (HCs), matched for demographic features, underwent neuropsychological tests for PM, executive functions, retrospective memory and self-rated questionnaires. The three groups did not differ on neuropsychological variables except for TBPM where TD-PD and CD patients performed worse than HCs; moreover, TD-PD performed worse than CD patients. Moderation analysis indicated that the type of movement disorder moderated the relationship between executive dysfunction and TBPM, but not EBPM. In conclusion, selective deficit of TBPM characterizes both CD and TD-PD but it is associated with executive dysfunction only in TD-PD. It might be possible to speculate that the involvement of the cerebellum, responsible for internal timing processes, could explain the impairment of TBPM in both movement disorders. This issue deserves to be explored in future neuroimaging studies.