Sex Differences in Cognitive Task Performance and Dendritic Arborization

Dendrites are branched neuronal structures that play a key role in communication via signal integration. Complex dendrites are believed to affect signal transmission where complexity and more dendritic spines are perceived to have more surface area for signal inputs, causing better communication within the brain. Therefore, it is important to explore if dendritic complexity is linked to sex differences in behavioral task performance. The current study placed 14 male and 14 female adult rats in the 5-Choice Serial Reaction Time Task (5CSRTT) for a total of 9 weeks. This cognitive-based task gets increasingly difficult as the rats progress to a new stage. Results from this showcased a sex difference in performance, where males outperformed females on various outcome measures. From this, a learning index (LI) was developed to assign each animal a score for overall performance. Males had higher overall LIs. It is unknown whether a relationship between sex-dependent 5CSRTT performance and dendritic morphology and spines exists. Thus, it was hypothesized that males would have greater arborization (dendritic length and number of bifurcations) and spine count and density in the anterior cingulate (ACC), infralimbic (IL), and prelimbic (PRL) cortices of the medial prefrontal cortex (mPFC). Apical and basilar dendrites of layer II/III pyramidal neurons of the mPFC were imaged. No sex differences were observed nor were there any significant relationships between the LI and any of the outcome measures. However, apical dendrites had significantly higher spine densities versus basilar dendrites in the ACC and IL, indicating that there are more predicted spines on apical dendrites than basilar dendrites. While a sex difference was not observed, given that apical dendrite’s functionality is to communicate to cortical and global subcortical regions, suggests that remote regions are involved and should be explored. Overall, sex difference in performance was not associated with a sex difference in dendritic morphology and spines.