Event-related potentials reveal memory deficits in Parkinson's disease

To evaluate whether patients with Parkinson's disease (PD) exhibit deficits in memory tested indirectly, we measured event-related potentials (ERPs) in 23 patients with nondemented PD and 14 age-matched control subjects. The auditory N400 component was measured during an indirect repetition priming paradigm. Some words were repeated immediately after initial presentation (lag 0), while others were repeated after five intervening words (lag 5) or at lags 11-77. Subjects were required to push a button to the occasional nonwords (targets). The N400 amplitudes were quantified in latency window between 300 and 800 ms for the different conditions. The N400 amplitudes for the first presentation were significantly lower in PD patients than controls for both words and nonwords. The N400 in the control group was attenuated for lag 0, lag 5, and lags 11-77 repetitions, while the attenuation in PD patients was noted only for lag 0 repetition. The data suggest that memory assessed in this fashion is impaired in PD patients.