Nirao Shah, PhD

Department of Psychiatry and Behavioral Sciences and Department of Neurobiology
Stanford University
(April 13, 2021)

Neural control of sexually dimorphic social behaviors

While the idea that “women are from Mars, men are from Venus” is overused (and outdated), it is true that some social behaviors are to a certain extant innate. Male and female brains use different signals and circuits for social behaviors, such as mating and aggression. Using animal models, Dr. Shah has found specific neurons in two brain areas, the amygdala and the hypothalamus, that regulate female mating behavior, and that connections between these neurons change during the ovulatory cycle. This work can give insight into how genes and neural connections give rise to particular behaviors.

Nirao ShahOur long term goal is to define the molecular and neural networks that regulate sexually differentiated physiology and behavior.  The behaviors that we focus on are social behaviors such as mating, territorial aggression, and maternal behaviors.  These behaviors are innate in the sense that they can be displayed without prior training.  Although these behaviors are the result of developmentally programmed pathways, we and others have shown that they are nevertheless responsive to social context and prior experience.  We leverage our understanding of sex determination, development, and physiology to achieve our goals, working primarily in mice but also with fruit flies and prairie voles to answer specific scientific questions.

Sexually dimorphic social behaviors emerge from sexually differentiated neural circuits, and we have employed identification of sex differences in gene expression or neuronal populations as a means to understand principles governing the display of these behaviors.  Key conceptual advances include the fact that male and female brains utilize distinct neural circuits for sex recognition, mating, and aggression.  Furthermore, the genetic and neural networks that regulate sexually dimorphic social behaviors are highly modular, with different genes and neural pathways regulating one or a few aspects of an individual social behavior but not other behaviors.

Recent studies from our lab have identified specific neurons in the hypothalamus and amygdala that regulate sex recognition and female mating behavior.  In addition, we have observed a remarkable plasticity in the neural circuit that regulates female mating, with connections shrinking and expanding 3-fold across the ovulatory cycle.  These connections peak at ovulation and enable the female to mate, thereby ensuring reproductive displays centered around the window of fertility.  In my presentation, I will discuss these findings and more recent follow up studies that shed mechanistic insights into the molecular and neural underpinnings of these behaviors.