Professor of Genetics, Genomics and Development*
*Affiliate, Division of Neurobiology, and Member of the Helen Wills Neuroscience Institute
We study taste recognition in the fruit fly, Drosophila Melanogaster, to examine how sensory information is processed by the brain. We use a combination of molecular, genetic, electrophysiological and behavioral approaches to study taste circuits. Our aims are to understand how different tastes are distinguished by the brain and how taste percepts and behaviors are modified by experience.
Drosophila, like mammals, detects tastes with modality-specific taste cells, including sugar-, bitter- and water-sensing cells. Inducible activation of these different cell populations is sufficient to trigger taste acceptance or rejection behavior. The tight link between gustatory detection and behavior, coupled with the approaches to manipulate and monitor neural activity and behavior, allows circuit dissection with cellular resolution. Determining the connectivity and function of neurons in this circuit will provide insight into how sweet and bitter interact in the brain to produce acceptance or rejection behavior and how internal states such as hunger or learning modify these responses.
Information processing in the brain. The subesophageal zone of the fly brain contains both axons of gustatory neurons and dendrites of motor neurons involved in taste behaviors. This suggests that the fly may have simple and localized taste circuits, with few connections between sensory stimulus and motor response. In addition, projection neurons may relay gustatory information to higher brain centers, perhaps for more complex associations. We are interested in mapping the functional and anatomical components of taste circuits using a variety of approaches. Genetic approaches to label subsets of neurons in the brain, behavioral screens for taste mutants, calcium imaging of taste responses in the brain and EM studies will help elucidate these circuits. These studies will provide insight into the integration of gustatory cues and the difference between sweet versus bitter.
Modulation of taste behaviors by hunger and satiety. A remarkable feature of taste behaviors that is conserved from flies to man is that they are exquisitely sensitive to internal state. Animals dynamically adjust the probability of feeding to ensure that caloric consumption and energy expenditure are in balance. We are interested in the cues signify hunger, satiety, and thirst in the fly and how they act on neural pathways from taste detection to feeding initiation. The complex regulation of feeding provides an excellent system to examine how neuronal circuits process gustatory information in the context of metabolic state to shape feeding decisions.
Modulation of taste behaviors by learning. Learning from previous experiences can modify strong and innate behavioral drives, including the decision to initiate feeding. Although sensory detection of nutrients drives innate feeding behavior in Drosophila and mammals, responses to nutrients may be modified if previously associated with a noxious stimulus. We are examining how taste memories are formed and how they influence feeding decisions to uncover cellular and circuit mechanisms for behavioral plasticity.
Kim, H., C. Kirkhart, and K. Scott (2017). Long-range projection neurons in the taste circuit of Drosophila. eLIfe e23386. PMCID: 5310837
Jourjine N.*, B.C. Mullaney *, K. Mann, and K. Scott (2016). Coupled sensing of hunger and thirst signals balances sugar and water consumption. Cell, 166: 855-866. PMCID: 27477513.
Kirkhart C. and K. Scott (2015). Gustatory learning and processing in the Drosophila mushroom bodies. Journal of Neuroscience, 35: 5950-5958. PMCID: 4397596.
Harris D.T., B.R. Kallman, B.C. Mullaney, and K. Scott (2015) Representations of Taste Modality in the Drosophila Brain. Neuron, 86:1449-60. PMCID: 4474761
Pool A.H., P. Kvello, K. Mann, S.K. Cheung, M.D. Gordon, L. Wang, and K. Scott (2014). Four GABAergic interneurons impose feeding restraint in Drosophla. Neuron, 83: 164-177. PMCID: 24991960.
Photo Credit: Mark Hanson of Mark Joseph Studios
Last Updated 2019-01-18