CHARACTERIZATION OF HIGH-VOLTAGE SPINDLES AND SPATIAL MEMORY IN YOUNG, MATURE AND AGED RATS

EEG was recorded from rats of three age groups, and high voltage spind les (HVS) were measured during waking immobility. Total mean spindling times in 4- (young), 10- (mature) and 22- (aged) month-old rats were 0.3 +/- 0.1, 20.4 +/- 7.4 and 33.4 +/- 14.9 s, respectively. Spatial m emory was assessed in these rats using a discrimination version of the Morris water maze. Performance (as measured by number of choice error s) was compared with the extent of HVS activity by characterizing rats as ''spindling'' if the total average duration of HVS discharges exce eded 5 s, and ''non-spindling'' if these discharges averaged less than 5 s. Spindling and nonspindling rats had similar performance during t raining; however, on a 14-day retention trial, spindling rats had a si gnificantly higher mean error score of 2.8 +/- 0.5 compared with 1.2 /- 0.3 for nonspindling rats (p = 0.011). These results show that spin dling activity increases in mature and aged rats, and that HVS dischar ges may be an electrophysiological change that parallels the progressi on of brain dysfunction associated with memory impairment.