Biology

Dr. Rajyashree Sen
Postdoctoral Research Scientist Richard Axel Lab Zuckerman Institute - Columbia University

Abstract:

In my graduate work, I set out to understand how the nervous system transforms sensory information into appropriate motor action. I focused on an ethologically relevant defensive behavior in Drosophila melanogaster: backward walking. Prior work had shown that the activity of a cluster of  ‘command-like’ neurons, the Moonwalker Descending Neurons (MDNs), is necessary and sufficient for backward locomotion in flies (Bidaye et al., 2014). From this starting point, my PhD laid a framework towards understanding 1) when and how MDNs are activated and 2) how the motor command from MDNs is executed. I demonstrated that MDNs are activated by multimodal aversive cues – visual and mechanosensory. In response to visual threats, a specific population of visual projection neurons – the lobula columnar 16 (LC16) cells – acts via the MDNs to trigger visually-evoked backward-walking retreat in flies (Sen et al., 2017). In response to physical obstructions, another cluster of neurons – the TwoLumps Ascending neurons – relays tactile cues from the fly’s legs and body walls to MDNs, and triggers touch-evoked reversal of walking direction (Sen et al., 2019a, in revision). In addition to these input pathways, I identified several local interneurons in the fly ventral nerve cord (the functional analog of the mammalian spinal cord) that are critical for execution of backward locomotion (Sen et al., 2019b, in preparation). Taken together, my graduate work provides a circuit that captures how sensory information leads to the activation of a ‘command-like’ neuron and how activity in this neuron is translated into appropriate motor action.