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Christopher Potter Ph.D

Assistant Professor of Neuroscience
Center for Sensory Biology

Telephone Number: 443-287-4151
Fax Number: 443-287-7672

The Solomon H. Snyder Department of Neuroscience

The Center for Sensory Biology

Johns Hopkins University

School of Medicine

855 North Wolfe St.

Baltimore, MD 21205

Room: 434 Rangos Building

Neural Circuits Required for Drosophila Olfaction

A pivotal area of neuroscience is to understand how sensory information from the external environment is received, processed, and interpreted by the brain. For example, why does an apple smell like an apple, and an orange like an orange? Why do we find the odorant vanilla pleasant, but are repelled by the odorant cadaverine?  Our ability to ‘smell’ different odors is tightly linked to our sense of odor perception. Yet little is known about how odor perception is processed in the brain.

My lab functions at an intersection between systems and cellular neuroscience. We are interested in how neurons and circuits function in the brain to achieve a common goal (olfaction), but we also develop, utilize, and build tools (molecular and genetic) that allow us to directly alter neuronal functions in a living organism. We then determine how our neuronal manipulations have altered the behavior of an animal.

The primary goal of the lab is to characterize the anatomy, development, and function of neurons required for olfactory behaviors in the vinegar fly Drosophila melanogaster. An initial focus is on the projection neurons (mitral/tufted cells in mammals)- the output neurons of the antennal lobe that target to higher brain regions of the fly such as the mushroom bodies and lateral horn. We first carried out an exhaustive study of projection neuron anatomy with the logic that their stereotyped axonal projections might underlie biological functions. Indeed, we found that ‘fruity odors’, which represent food, and pheromones, which represent sex, signal to distinct regions of the lateral horn. This organization was further respected by lateral horn output neurons. They too showed specificity to either the ‘fruity’ or ‘sex’ regions of the lateral horn. Therefore, the lateral horn region, which to the naked eye looks quite homogeneous, might actually be organized into subdomains according to the biological meanings of the stimuli.

By using neurogenetics, we can label and manipulate small populations of neurons and assay their effects on olfactory behaviors. Such detailed genetic perturbations are possible using the ‘Q-system’ we have developed: a repressible binary expression system, that when used in combination with the GAL4 system, allows for genetic silencing or activation of small neuronal populations (See Figure). We have also developed a high throughput computer controlled olfactory attraction and repulsion behavioral assay. In this assay, hundreds of flies are tracked simultaneously as they respond to different odorants at many carefully controlled odorant concentrations. From such analyses, we can effectively and efficiently link precisely defined neuronal populations to their respective odorant behaviors. We have also established an electrophysiology rig to directly record the activity of antennal neurons in response to odor stimulations.

Current projects in the lab involve (but are not limited to): 1) characterizing the function of the projection neurons in relaying odorant information to higher brain centers; 2) characterizing the adult fly’s olfactory system in eliciting stereotyped attractive or repulsive behaviors to discrete odorants; 3) identifying and characterizing the neuronal circuitry required for innate olfactory responses to environmental stimuli ; 4) developing genetic tools for linking neurons to their function.

We are always looking for motivated graduate students, so if any of the above sounds interesting, email me to learn more about the lab.