Laterally asymmetrical cell number in a sexually dimorphic nucleus in the gerbil hypothalamus is correlated with vocal emission rates.

A lateralized relationship between the total volume of a discrete area in a hypothalamic, sexually differentiated nucleus (SDApc) and stereotyped vocalization exists in male Mongolian gerbils. In this present study, using unbiased stereological methods, two cytoarchitectural estimates of the SDApc's structure, neuron number, and nuclear volume were found to be sexually differentiated and also laterally asymmetrical in adult males. In ovariectomized females receiving exogenous testosterone, no cytoarchitectural component was asymmetrical. Significantly, the estimate of neuron number, but not nuclear volume, in the left SDApc of males was correlated with vocal emission rate. The authors conclude that a specific, sex-related cytoarchitectural SDApc parameter shows left-right asymmetry, suggesting the SDApc has an intimate role in mediating hemispheric specialization rather than just being an end point index of individual structural variability.