Section: Research

Scott Waddell, Ph.D.

Academic Role: Associate Professor

Faculty Appointment(s) In:
   Neurobiology

Other Affiliation(s):
   Interdisciplinary Graduate Program
   Program in Neuroscience

Drosophila Olfactory Memory

Studies over the last century have determined that memory exists in time-dependent phases and is converted from a labile to a stable state after training by a process termed consolidation. In mammals memory consolidation involves both parallel and sequential use of distinct brain regions. Consolidation initially requires the neural circuitry of the hippocampus and cortex but once the memory is consolidated, the requirement of the hippocampus is diminished. Hippocampal damage impairs the consolidation of new memories but leaves old memories intact suggesting that consolidated memories permanently reside in the cortex.

Using olfactory memory in the fruit fly Drosophila as a model, we are studying how memory is encoded and stabilized at the molecular, cellular and neural network level. Our work has established that the simpler fruit fly brain also employs parallel and sequential use of different regions to process memory.

Flies are taught to discriminate between odors following odor pairing with an electric shock punishment or with a sugar reward. Trained flies learn to either run away, or run toward, the appropriate odor. The reduced complexity of the fly brain (approx 250,000 neurons) and the fantastic genetic tool-kit make the study of memory in the fly readily accessible to precise interventionist analysis. Using the most up to date approaches, our work has established that distinct regions of the fly brain are involved at different times to process memory (Figure 1). Mushroom Body a´b´ neuron activity is required to form memory, Mushroom Body a´b´ neurons and Dorsal Paired Medial (DPM) neurons are transiently required to consolidate memory and output from Mushroom Body ab neurons is exclusively required to retrieve memory. We interpret these results to suggest that odor memories are formed in ab neurons, and are stabilized there by recurrent activity involving a´b´, DPM neurons and the ab neurons themselves. We therefore have broken down some of the memory-relevant brain circuits into discrete, but interacting, functional units and even down to the resolution of two neurons (DPM neurons). This work is likely to illuminate principles of neural circuit organization and function.

In addition, many conserved cell-signaling cascades have been implicated in fly memory and we aim to understand the neural circuit context in which these pathways are employed to encode memory.

Office: LRB 725
Phone: 508-856-6804
E-mail: Scott.Waddell@umassmed.edu
Keywords: Neurobiology, Organisms - Drosophila, Learning and Memory, Neural Plasticity, Genetics

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