Objective: To investigate whether temporal working memory (TWM) could be impacted in Parkinson’s disease (PD). We also tested whether idiopathic PD patients (iPD) could be differentiated from patients suffering of a genetic variant of the disease (Parkin) using this function as a biomarker. Moreover, the influence of dopaminergic medication on TWM was also investigated.

Background: Deterioration of working memory is a frequently observed consequence of PD. Independently, it has also been shown that temporal cognition is abnormal in these patients, although the precise nature of this deficit is unknown. The relationship between these two deficits is unknown but could be a precious indicator of progressive cognitive dysfunction.

Methods: A simple oculomotor task in which subjects had to make a visually guided saccade between a central and a peripheral target was used. The delay between the extinction of the central target and the appearance of the eccentric one was the independent variable experimentally manipulated and could take one of four different values randomly (400, 900, 1400, 1900 ms, referred to as ‘foreperiod duration’). Saccadic latency was the dependent variable measured.

Results: We found that saccadic latencies were on average significantly longer in 20 iPD (mean±std, ON, 374±169 ms, n=1939; OFF, 374±173 ms, n=2005) and 11 Parkin patients (ON, 335±155 ms, n=2492; OFF, 330±158 ms, n=2724) compared with 18 age and sex-matched controls (318±121 ms, n=4488). In all subjects, saccadic latencies were longer for short foreperiods and decreased for longer ones. This well-known foreperiod effect was preserved in iPD and Parkin patients, ON or OFF medication. In controls, the latency of saccades during the current foreperiod was also influenced by the duration of the foreperiod during the preceding trial. This TWM effect was altered in both iPD and Parkin patients, ON or OFF medication. However, the TWM deficit was statistically more pronounced in iPD than in Parkin patients suggesting that this difference is unlikely related to the dopaminergic system.

Conclusions: Temporal working memory could be a reliable indicator of memory dysfunction in PD. Dopaminergic treatment did not counteract this observed deficit. Moreover, the extent of the deficit was different in iPD and Parkin patients, suggesting that it may be mediated by a prefrontal dysfunction.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/temporal-working-memory-deficit-in-parkinsons-disease/