Latent learning of spatial information is impaired in middle-aged rats

The present study determined if the middle age related impairment that occurs with nonspatial latent learning also occurs in spatial latent learning. Thirty young (3-months-old) and 30 middle-aged (12-months-old) male Sprague-Dawley rats were given either pre-exposure to spatial cues surrounding a Barnes maze (SpatialPX), or pre-exposure to just the maze (MazePX). They were then given 10 training trials in which they had to find a hidden escape box while experiencing an aversive environment produced by bright lights and wind. Results showed that young rats given the SpatialPX condition demonstrated faster escape latencies and fewer errors than young rats given the MazePX condition. However, middle-aged rats given the SpatialPX condition did not show this improved performance. These findings indicate that the middle age learning deficit is not task specific, but rather is a general impairment in latent learning, possibly due to the early degeneration of the entorhinal cortex.