FIGURE 13.2. Odor-evoked population dynamics.


Odor-evoked population dynamics. (A) Construction of a population vector. For any time bin (t0 to tN), the nth dimension of the vectors corresponded to the average firing rate (FR) of the nth-recorded cell. (B) Average trajectory of the population vector (eight bins per cycle, from −2.5 to 4 s relative to odor onset) before and after hexanone 0.20 application and visualized in PCA space. Two different viewing angles are shown. Two types of dynamics are visible: slow dynamics reflecting changes of firing across respiratory cycles, and fast pseudocyclic dynamics reflecting breathing cycle internal dynamics. (C) Comparison of high-and low-resolution descriptions of slow temporal dynamics. Population vector trajectories become stable after going through a slow transient. The rapidity of this process was measured by computing the velocity of the population vector averaged over 312 ms time bins (i.e., mean breathing cycle duration). However, it is conceivable that the cyclic trajectories themselves converge with a different timing as their average. In this figure, the distance between successive cycle trajectories (a cycle trajectory represented by the concatenation of its decomposition in eight population vectors) and successive cycle averages (i.e., the average population vector over a breathing cycle) are plotted. All points are normalized by the observed baseline value. These velocity measures indicate that the convergence of cycle trajectories occurs within the same time period as their average (roughly 1 s to reach a steady state). Fitting a single exponential function on the curves also yields similar time constants (386 ms for the cycle average and 499 ms for the cycle trajectories). Therefore, both convergences probably result from the same dynamical process. ([A–C] Adapted from Bathellier, B. et al. Neuron., 57, 586–98, 2008a.)

From: Chapter 13, Temporal Coding in Olfaction

Cover of The Neurobiology of Olfaction
The Neurobiology of Olfaction.
Menini A, editor.
Boca Raton (FL): CRC Press/Taylor & Francis; 2010.
Copyright © 2010 by Taylor and Francis Group, LLC.

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