- Molecular Biology/Princeton Neuroscience Institute
- The McDonnell Center for Systems Neuroscience
Our research focuses on addressing two fundamental questions in neuroscience: how does the brain convert sensory stimuli into meaningful representations, and how do these representations drive behavioral responses? Drosophila, with its relatively simple nervous system, robust and complex behaviors, amenability for in vivo electrophysiology, and large genetic and molecular toolkit offers an ideal system in which to examine questions about sensory coding. We concentrate our efforts on two sensory pathways: auditory and olfactory.
AUDITION : Flies communicate using sounds during their courtship ritual; male flies generate sound via wing vibration while females are faced with the task of recognizing song, based on its species-specific parameters, and choosing a particular mate, based in part on differences in song between conspecific individuals. This problem is analogous to one other animals, such as the songbird, must solve. While flies are cognitively limited compared to birds (for example, flies do not learn their songs), their capacity to recognize and respond to species-specific sounds with so few neurons is striking, and suggests that studying flies will reveal insight into the basic requirements for communication.
We are asking: what features of song do females utilize when deciding to mate? how is song feature detection accomplished by neurons of the auditory pathway? how do neural representations of courtship songs shape behavioral responses? And, what effect does experience have on song perception? We utilize a combination of genetic, behavioral, imaging, in vivo electrophysiological, and computational methods to address these questions. The ability to quantify the natural acoustic environment for Drosophila (in terms of temporal pattern, frequency, and amplitude) and the fact that auditory behaviors (courtship and mating) are very robust in flies facilitates our quantitative analysis of both behavior and neural recordings. Inspired by the recent sequencing of twelve Drosophila genomes and the potential for the development of genetic tools across species, we are also taking a comparative approach to understanding the neural coding of courtship song by presenting auditory stimuli from and performing electrophysiological recordings in several of these species.
OLFACTION : In the mushroom body, the fly’s olfactory learning and memory center, we have discovered that each fly possesses a complement of Kenyon cells (KCs; the principal neurons of the mushroom body) whose odor tuning differs from individual to individual. This study defined a method for measuring the across-animal variability of individual neurons within a large population, using a combination of genetic labeling, single-cell electrophysiology, and computational models. Using similar methods, we are following up on these results by recording from the postsynaptic targets of the KCs, the mushroom body extrinsic neurons (MBEs). Among this smaller population we can investigate whether or not functional stereotypy reemerges downstream from the KCs, and if so, how. We can also explore how olfactory memories (positive and negative associations) are formed in this structure, and the overall logic of olfactory coding within the mushroom body.
1. Tootoonian, S, Coen, P, Kawai, R, and Murthy, M. Neural representations of courtship song in the Drosophila brain. Journal of Neuroscience. 2012 Jan;32(3): 787-798.
2. Murthy, M and Turner, G. In vivo whole-cell recordings in the Drosophila brain. Drosophila Neurobiology: A Laboratory Manual. Ed. Zhang B, Freeman MR, Waddell S. CSHL Press. June 2010
3. Murthy, M. Unraveling the auditory system of Drosophila. Current Opinion in Neurobiology. 2010 June;20(3):281-7.
4. Murthy, M, Fiete, I, and Laurent, G. Testing odor response stereotypy in the Drosophila mushroom body. Neuron. 2008 Sep 25;59(6):1009-23.