Sex differences in implicit memory:an fMR1 study using weather prediction probabilistic classivication task

Several recent studies have shown sex-related differences in the neural organization of memory processes. However, as the majority of investigations involved explicit memory tasks, little is known about potential differences between men and women in the organization of implicit memory processes. Our study addressed this issue. We used functional magnetic resonance imaging (fMRI) to compare the patterns of brain activity in men and women performing the weather prediction probabilistic classifi cation task which is a tool for assessing implicit learning. In this task, subjects learn to predict the weather using associations that are formed gradually across many trials, because of the probabilistic nature of the cueoutcome relationships. Although both men and women exhibited similar level of behavioral performance, between-sex group analysis of the BOLD response demonstrated greater activity in men than in women in dorsolateral prefrontal (BA 9, 46), parietal (BA 7, 40), and occipital (18, 19) cortices. In contrast, women activated insular (BA 13), temporal (BA 21, 22) and ventrolateral prefrontal (BA 44) cortices. Differences between men and women in the patterns of brain activity might refl ect distinct strategies used in the weather prediction probabilistic classifi cation task. Our results indicate that neural activity underlying implicit memory differs between sexes, despite of lack of differences in behavioral effi - ciency.