Week 5: Tuning Triphasic Odor Response

Last week we successfully coded odor stimulation. Now, we need to make sure that our model responds to it properly. Odor stimulus elicits a triphasic response within Antennal Lobe projection neurons (PNs).

The first phase is a brief hyperpolarization, where the PN voltage dips at the onset of odor. Next is a period of high firing rate, where firing varies between PNs from homogeneous firing to bursting firing. Finally, there is a hyperpolarization following the end of the odor characterized by extremely low PN firing rates. Our goal this week is to achieve all three of these phases in our model.

 

After enough tuning, we eventually were able to make all of these properties emerge. In order to get the first phase behavior, we found that the fast inhibition signal from local neurons (LNs) to PNs played the most substantial role in the brief hyperpolarization. The variation in firing behavior during the high firing phase was largely controlled by the SK currents of the PNs. Having a higher SK current value led to more bursting behavior, while a lower SK current value led to more homogeneous firing behavior. Finally, the hyperpolarization following the odor presentation seemed mostly controlled by the slow inhibition coming from LNs. Phase one and phase three greatly exemplify the important role LNs have in shaping the dynamics of odor perception. Shown below is a graph showing parameters of a single PN during a simulation, as well as a raster plot showing the dynamics of the entire Antennal Lobe during a simulation. Odor onset occurs at the 1 second mark, and the odor dissipates by the 2nd second. Both of these graphs show evidence of the triphasic response within our model.

 

ExamplePN

Raster

 

Now that odor perception is relatively well tuned, we are interested in beginning to explore sensory integration. In order to integrate two senses, we first need to code the second type of stimulation. Next week, we will continue on this project by creating mechanosensory stimulus, with the intention of heading towards our goal of sensory integration.

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