Short-term plasticity in early olfactory information processing

For Drosophila, olfaction starts from the binding of odor molecules to the surface of olfactory sensory neurons (ORNs) and triggers action potentials that are relayed to higher brain regions by second-order projection neurons in the antennal lobe (AL). Two characteristics of this early olfactory information processing are important for odor coding. First, response of a PN to its cognate ORN is normalized by the overall activity of other ORNs, a phenomenon termed “divisive normalization”. Second, PNs respond strongly to the onset of ORN activities, but they adapt to prolonged or continuously increasing inputs. Despite extensive experimental studies and phenomenological modeling of this system, the underlying mechanism of these characteristics remains not fully understood. In this work, we developed a simple neural circuit model based on the known incoherent feedforward architecture in AL, which includes key factors in neuronal interactions such as short-term plasticity (STP) and presynaptic inhibition by local neurons (LNs). By using both analytical and numerical methods, we studied the steady state and dynamic properties of our model and compared the results with existing experimental data. The quantitative comparison between our model and experiments revealed that STP is crucial for the observed nonlinear divisive normalization, and both STP and PI contribute to the highly adaptive response of PNs to time-varying inputs.

Y. Liu, Q. Li, C. Tang, S. Qin^†, and Y. Tu^†. “ Short-Term Plasticity Regulates Both Divisive Normalization and Adaptive Responses in Drosophila Olfactory System”. Frontiers in Computational Neuroscience 15, 730431(2021). (^† corresponding authors)