INDIVIDUAL-DIFFERENCES IN SPATIAL MEMORY AND STRIATAL CHAT ACTIVITY AMONG YOUNG AND AGED RATS

Individual differences in spatial memory among young and aged rats wer e assessed using memory tasks related to integrity of the hippocampus and the neostriatum. Relationships were then examined between measures of spatial memory and regional choline acetyltransferase (ChAT) activ ity, a marker for cholinergic integrity. Twenty-four-month-old Long-Ev ans rats were impaired in comparisons with B-month-old rats on measure s of place learning, working memory, reference memory, and perseverati on in water-maze tasks. Aged rats that were impaired on one measure of memory, however, were not necessarily impaired on other measures. ChA T activity in the ventromedial and dorsolateral neostriatum of aged ra ts was significantly reduced in comparisons with young rats whereas no difference was found in the hippocampus. Aged rats with the most ChAT activity in the anterior ventromedial neostriatum performed best on t he place-learning and reference memory tasks but also made the most pe rseverative errors on the working memory task. In addition, young and aged rats with the most ChAT activity in the anterior dorsolateral neo striatum were those with the least accurate working memory. No relatio nships were found between ChAT activity in the hippocampus and spatial memory. Thus age-related memory impairment has components that can be segregated by measuring relationships between cholinergic integrity i n subregions of the anterior neostriatum and memory tasks with differe nt strategic requirements. (C) 1998 Academic Press.