Middle-aged (12 month old) male rats show selective latent learning deficit

While many cognitive aging studies have been conducted using old (20+ months old) rats, few have demonstrated cognitive deficits in middle-aged (12 months old) rats. The present study was conducted to determine if deficits in latent learning (the acquisition of neutral information that does not immediately influence behavior) arise during middle age in rats. Twelve young (3 months old) and 12 middle-aged male Sprague-Dawley rats completed the latent cue preference (LCP) task, a conditioned cue preference (CCP) task in the same apparatus, and a reinforced spatial learning task using the Barnes maze. Results showed that the middle-aged rats were impaired on the latent learning (LCP) task relative to the young rats, but were not impaired on the CCP task or the spatial learning task. This may be because latent learning requires a functional entorhinal cortex, and the entorhinal cortex is one brain region that shows early age-related functional degeneration.