Short-term temporal memory in idiopathic and Parkin-associated Parkinson's disease

In a rapidly changing environment, we often know when to do something before we have to do it. This preparation in the temporal domain is based on a 'perception' of elapsed time and short-term memory of previous stimulation in a similar context. These functions could be perturbed in Parkinson's disease. Therefore, we investigated their role in eye movement preparation in sporadic Parkinson's disease and in a very infrequent variant affecting the Parkin gene. We used a simple oculomotor task where subjects had to orient to a visual target and movement latency was measured. We found that in spite of an increased average reaction time, the influence of elapsed time on movement preparation was similar in controls and the two groups of PD patients. However, short-term temporal memory of previous stimulation was severely affected in sporadic PD patients either ON or OFF dopaminergic therapy. We conclude that the two different contributions to temporal preparation could be dissociated. Moreover, a short-term temporal memory deficit might underlie temporal cognition deficits previously observed in PD.