Meeting Abstract
Sexually dimorphic behavior is often correlated with variation in relative and absolute sizes of brain regions. However, few studies have tested whether this also extends to neuronal morphology within brain regions of wild species. Richardson’s ground squirrels (Urocitellus richardsonii) exhibit sexually dimorphic social behavior; females being far more tolerant of other individuals and less aggressive than males. Because the prefrontal cortex plays a key role in modulating social behavior, we hypothesized that the neuronal morphology within the prefrontal cortex is sexually dimorphic in Richardson’s ground squirrels. We used virtual microscopy to image Golgi stained pyramidal neurons within the medial prefrontal (mPFC) and orbitofrontal (OFC) cortices of wild caught male and female ground squirrels. From these images, we traced over 180 neurons across both regions and quantified 17 different measurements of neuronal morphology. Mixed models revealed that soma and total neuron volumes are significantly larger in males than females within the OFC. Convex hull and basal dendritic volumes are also significantly larger in males than females in the mPFC. Thus, males tend to have larger neurons with broader dendritic trees, despite a female bias in mPFC volume. Males are larger than females, so these sex differences in neuronal morphology likely reflect larger male brains rather than sexually dimorphic behavior. We suggest that other variables might be more closely associated with sexual dimorphism in Richardson’s ground squirrel social behavior, such as dendritic spine density or nonapeptide receptor distribution.
