[Memory function in aging and Parkinson's disease--an event-related potential study]

The N400 of event-related potentials (ERPs) was recorded in 17 healthy young subjects (mean age 24.4 years), 14 healthy old subjects (healthy control subjects, mean age 62.7 years), and 21 patients with nondemented Parkinson's disease (PD, mean age, 63.8 years) as they listened to words or nonwords. Some words were repeated immediately after the initial presentation (2 sec), while others were repeated after 5 intervening words (12 sec) or after 2 to 4 minutes. The subjects were required to respond to occasional nonwords. Rey's auditory verbal learning test(AVLT) was also performed. The mean N400 amplitude was smaller in patients with PD than in either healthy group, but there was no difference between the two healthy groups. In the young subjects, N400 was attenuated for repeated words, and the attenuation was more pronounced for immediate than for delayed repetitions. N400 attenuation in the old subjects was more markedly reduced as the interval between the 1st and 2nd presentation increased than in the young subjects. In PD patients, attenuation was noted only for immediate repetition. Free recall by the old subjects was impaired relative to the young subjects throughout the AVLT trials, and was even more impaired in patients with PD. In addition, the number of free recalls increased less with the number of trials in patients with PD than in the old subjects. These results may indicate that episodic memory declines with advancing age, and declines even more in patients with PD. In addition, the ability to transform information form short-term memory to long-term memory appear to be impaired in patients with PD.