Castration differentially affects spatial working and reference memory in male rats

A male advantage for spatial learning and memory tasks is well documented among humans and rodents. A possible physiological cause for this male advantage is activational effects of androgens among males. The spatial memory of eight castrated and eight sham-castrated adult male rats was compared using a working-reference memory version of the eight-arm radial arm maze followed by a reference memory version of the Morris water maze. After maze testing, blood was collected from each rat, and testosterone levels were determined using radioimmunoassay. In the radial arm maze, castrates committed significantly more working memory errors and significantly fewer reference memory errors than did shams. In the water maze, no statistically significant differences were found for acquisition or retention. There was a trend for shams with higher testosterone levels to have better retention in the water maze, but this seemed to be due to higher levels of perseverance rather than better reference memory. Castration may have affected performance in the radial arm maze and not in the water maze because the radial arm maze was a more difficult task or because the water maze was aversively motivated while the radial arm maze was appetitively motivated. Our results indicate that androgens improve working memory and may impair reference memory, but the effects of androgens on reference memory seem to be task dependent.