Past events

Sexually reproducing animals display sex-specific behaviors wired onto dimorphic connectivity patterns in the nervous system. The mechanisms underlying the development of sexually dimorphic nervous systems that consists mainly of shared neuronal types remain largely unknown. Within the nervous system, males and females display a number of anatomical sexual dimorphisms often in the form of neurons that are present exclusively in one, but not the other sex. In this talk I will focus on sex-specific wiring of neurons that are present in both sexes, and demonstrate the sex-specific functions of sex-shared neurons in C. elegans. The key finding that I will present is that sex-specific wiring patterns are the result of sex-specific synaptic pruning events. I will show that many neurons initially form synapses in a non-discriminatory manner in both the male and hermaphrodite pattern before sexual maturation, but sex-specific pruning events result in the sex-specific maintenance of subsets of the connections. I will describe the behavioral tests taken to show that rewiring is indicative of repurposing of the function of sensory and interneuron. I will present the conserved genes I uncovered that function to determine sex-specific connectivity patterns. To summarize I will discuss how the sexual identity of individual neurons, by initiating selective synapse loss, refines the circuitry and defines sex-specific synaptic targets. This allows for diversification of behavioral outputs with a limited set of shared neurons.

Striatal disinhibition leads to spontaneous abnormal action release manifesting as motor tics, resembling those expressed in Tourette syndrome patients. We utilized microstimulation within the motor cortex of freely-behaving rats before and after striatal disinhibition to study the spatial and temporal properties of tic expression. The spatial properties of these tics were dependent on the striatal organization while the temporal properties were dependent on the cortico-striatal activity. A data-driven computational model of cortico-striatal function closely replicated the temporal properties of abnormal action release. These converging experimental and computational findings suggest a clear functional dichotomy within the cortico-striatal network, pointing to disparate temporal (cortical) vs. spatial (striatal) encoding of action release.