Recognition memory in normal aging and Parkinson's disease: behavioral and electrophysiologic measures

To assess effects of normal aging and Parkinson's disease (PD) on recognition memory, we examined the N400 component of event-related potentials (ERPs) and behavioral measures during a recognition memory task in 17 normal young subjects, 17 normal elderly subjects, and 17 patients with PD. To elicit ERPs, some words were repeated immediately after initial presentation (at lag 0), while others were repeated after one intervening word (at lag 1) or at lag 6. Subjects were requested to push a button with the right thumb upon first presentation of a word and with the left thumb upon repeat presentation. Compared to the normal young subjects, normal elderly subjects showed reduced accuracy in recognizing repeated words at lags 1 and 6. Compared to the normal elderly group, PD patients showed decreased accuracy in recognizing lag 6 repetition. N400 amplitude did not differ between the two normal groups, while PD patients showed lower N400 amplitudes than normal elderly subjects. The N400 in the young group showed attenuation for lags 0, 1 and 6 repetitions, while attenuations in the elderly group and the PD group were noted only for lags 0 and 1 repetitions. These data suggest intact immediate but impaired delayed recognition memory in aging and in PD. In addition, recognition memory deficits in PD may result, at least partly from the impairment of context integration process.