Abstract
Dynamical changes in the environment strongly impact our perception. Likewise, sensory systems preferentially represent stimulus changes, enhancing temporal contrast. In olfaction, odor concentration changes across consecutive inhalations (ΔCt) can guide odor source localization, yet the neural representation of ΔCt has not been studied in vertebrates. We have found that, in the mouse olfactory bulb, a subset of mitral/tufted (M/T) cells represents ΔCt, enhancing the contrast between different concentrations. These concentration change responses are direction selective: they respond either to increments or decrements of concentration, reminiscent of ON and OFF selectivity in the retina. This contrast enhancement scales with the magnitude, but not the duration of the concentration step. Further, ΔCt can be read out from the total spike count per sniff, unlike odor identity and intensity, which are represented by fast temporal spike patterns. Our results demonstrate that a subset of M/T cells represents ΔCt, providing a signal that may instruct navigational decisions in downstream olfactory circuits.
Significance As an animal tracks an odor plume, concentration changes over time. Here we show that olfactory bulb neurons explicitly represent concentration changes between consecutive inhalations. This response property enhances temporal contrast, as in other sensory systems. Fine temporal spike patterns do not improve concentration change decoding. These signals may guide olfactory navigation in the natural environment.
Footnotes
Conflict of interest: No
Israel Science Foundation grants 816/14 and 2212/14 (R.S)
Marie Curie Career Integration grant 334341 (R.S.)
NIH/NICDC grants: R56DC015584 (R.S. and M.S.)
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
