An evaluation of spatial information processing in aged rats.

The spatial learning abilities of young, middle-age, and senescent rats were investigated in 2 experiments using several versions of the Morris water maze task. In Exp I, Long-Evans hooded rats were trained to find a submerged escape platform hidden within the water maze. Aged Ss exhibited acquisition deficits compared with either young or middle-age Ss. With continued training, all age groups eventually achieved comparable asymptotic levels of performance. To identify the basis of the age-related impairments observed in Exp I, naive young and aged Ss in Exp II were initially tested for their ability to locate a cued escape platform in the water maze. The escape latencies of both young and aged Ss rapidly decreased to equivalent asymptotic levels. Following cue training, young Ss exhibit a significant spatial bias for the region of the testing apparatus where the platform was positioned during training. In contrast, aged Ss showed no spatial bias. Training was continued in Exp II using a novel submerged platform location for each S. During these place training trials, the escape latencies of senescent Ss were longer than those of young Ss. These impairments were also accompanied by a lack of spatial bias among aged Ss relative to young controls. Results indicate that age-related impairments in water maze performance reflect a specific deficit in the ability of aged rats to utilize spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)