Our lab at CSHL is interested in how the brain accomplishes the ongoing transformation from sensation to action during natural behaviors. Vocal communication, which requires the integration of auditory inputs to generate appropriate motor responses is ideally suited to study sensorimotor transformations. Humans engaged in conversation, for example, take rapid turns to go back and forth between listening and responding. Recently, we have discovered that a neo-tropical rodent engages in similarly fast vocal interactions, even under laboratory settings. In my post-doctoral research, I have laid down the foundation for studying a flexible, natural behavior in a highly vocal rodent species – Alston’s singing mice (Scotinomys teguina). The research goal is to determine the brain-wide neural circuits that allow flexible vocal communication in mammals using this novel system.
Towards that goal, using causal manipulations, I showed that an orofacial motor cortical area (OMC) in this rodent is required for vocal interactions (Okobi*, Banerjee* et. al, 2019). Subsequently, in electrophysiological recordings, I found neurons in OMC that track initiation, termination and relative timing of songs (Banerjee et al, in preparation). These results demonstrate robust cortical control of vocal timing in a rodent and upends the current dogma that motor cortical control of vocal output is evolutionarily restricted to the primate lineage. However, to generate the back-and-forth of the conversation, motor cortex (OMC) cannot act in isolation. The next logical step is to understand how the auditory system interacts with the motor system, which is required for vocal communication. Using chronic electrophysiology, multiphoton microscopy, viral tracing and causal circuit manipulations (for e.g. optogenetics), I will test the hypothesis that integration of specific contextual cues (e.g. auditory input) with the song production pathway is dependent upon cortical function.
FIG. 1: Phenotypic variation in vocalizations of four small rodents including the lab mouse and Alston’s singing mouse. Structural and functional changes that give rise to behavioral novelty is not known. (Spectrograms from the Phelps lab, U.T. Austin)
Following Dobzhansky’s famous dictum that “Nothing in biology makes sense except in the light of evolution”, my long-term goal is to understand what neural circuit modifications underlie acquisition of novel behavioral phenotypes during evolution.
Recent work indicates that a small number of genes can control the evolution of complex innate behaviors (Metz et al, 2017). Genes that determine such behavioral differences must act via neural circuits within the brain. Yet, to date, what brain structural and functional changes accompany the acquisition of such novel behaviors remain unknown, primarily because the neural circuits underlying these complex behaviors have not been deciphered. The singing behavior in S. teguina combined with our knowledge of the relevant neural circuitry offers a rare opportunity to bridge this knowledge-gap. Using a comparative approach, I will test the hypothesis that cortical control of vocal interactions is determined by a small number of neural circuit modifications across closely related species (Fig. 1).
Overall, research in the lab combines cutting-edge neural circuit analysis of a natural behavior with comparative evolutionary analyses across closely-related species to gain insight into the evolution of neural circuits for mammalian vocal communication.