Cortical feedback and gating in odor discrimination and generalization

Abstract

A central question in neuroscience is how context changes perception of sensory stimuli. In the olfactory system, for example, experiments show that task demands can drive merging and separation of cortical odor responses, which underpin olfactory generalization and discrimination. Here, we propose a simple statistical mechanism for this effect, based on unstructured feedback from the central brain to the olfactory bulb, representing the context associated with an odor, and sufficiently selective cortical gating of sensory inputs. Strikingly, the model predicts that both pattern separation and completion should increase when odors are initially more similar, an effect reported in recent experiments. The theory predicts reversals of these trends following experimental manipulations and neurological conditions such as Alzheimer's disease that increase cortical excitability.

Connectivity and dynamics in the olfactory bulb

“…This model also supports findings on feedback-driven odor discrimination and generalization from a statistical model presented in [53].…”

“…Our model reproduced important empirical features of the OB, including differential connectivity patterns among sister and non-sister MCs, decorrelation over short timescales, as well as theta, beta and gamma oscillations in the local field potential (LFP). The model makes the surprising, and testable, prediction that cortical feedback inhibition of MCs via GCs is a network property largely independent of which GCs are targeted, an observation with consequences for our understanding of how context modulates odor representations [28,[44][45][46][47][48][49][50][51][52][53], and for theories of the functional purpose of granule cell neurogenesis [12,21,26,36]. The model also predicts that beta and gamma oscillations, which are implicated in numerous theories of odor coding and decoding [54][55][56][57], are network properties intrinsic to the bulb that can be modified, July 19, 2021 2/34 suppressed, or enhanced by the density of granule cell activity [14,23,39].…”