ELECTROPHYSIOLOGIC FUNCTION IN THE HEALTHY, EXTREMELY OLD

We analyzed conventional EEG, computerized EEG frequency analysis (CEEGFA), and long-latency auditory evoked potentials in 22 extremely healthy subjects over age 84 (range, 84 to 98) and compared them with 11 younger elderly subjects as well as subjects under age 65 years. Intermittent temporal slowing in the conventional EEG was present in 50% of the elderly. Its presence was related to the presence of white matter hyperintensities on MRI but not to blood pressure or cognitive function. The posterior peak frequency determined by CEEGFA was maintained above 8 Hz in all subjects under age 84, but was between 7 and 8 Hz in five of 22 subjects over age 84 years. Three other CEEGFA variables studied (relative theta, relative alpha, and median-power frequency in the posterior channels) all demonstrated a significant change with age, most marked above age 80 years. Well-defined P3s were not present in five of 22 subjects over age 84 and in only one of 38 subjects under age 84 years. The P3 latency increased by 0.8 msec per year throughout the adult age range, while the P3 amplitude was relatively stable until the eighties. This study highlights the effects of healthy aging on clinical electrophysiologic tests of cerebral function.