Is Sensory Processing about Detecting Abrupt Changes in the Sensory World?

Abstract

Event Abstract Back to Event Is Sensory Processing about Detecting Abrupt Changes in the Sensory World? One of the most salient properties of the sensory system is its propensity to respond strongly to transient rather than to static stimuli. This marked preference for changes is found in the brain at all levels. A variety of mechanisms are known to boost responses to higher temporal frenquencies such as short-term synaptic depression, spike rate adaptation and feedforward inhibition. However, change detection as a major role of sensory processing remains largely unexplored. In order to test this hypothesis, we use a novel probabilistic framework and show quantitatively the importance of feedfoward inhibition in detecting sudden "appearance" (or "desappearance") of stimuli. Assuming a Markov dynamics of stimuli, we derive an "ideal observer" that computes on-line a probability of a sudden change in input firing rates (a transition). In general, this model predicts a bi-phasic, non-linear synaptic integration consisting of a fast, transient, excitation followed by a slower inhibition. The same stimulus that excites the cell at short delays inhibits it at longer ones. However, the exact properties of this integration, in particular the strength and time constants of excitation and inhibition depend on the temporal statistics of the stimulus and the reliability of the input spike trains : in noisier settings, longer integrations are required to detect changes. We explore what this general framework implies for temporal receptive fields (tRFs), contrast adaptation and spike-time precision in early visual areas. We suppose that output spikes are generated when the probability of transition crosses a threshold, followed by a refractory period. This spike generation mechanism reproduces the firing statistics in the retina and LGN in response to time varying stimuli. Particularly sharp peaks in PSTH that could not be predicted directly from the linear tRFs, but instead could be obtained by adding feedforward inhibition and refractoriness. The predicted tRFs resemble the ones of "ON" and "OFF" retinal ganglion cells and LGN cells, but their shape adapts to the (variance of the) contrast of the input. At low contrast, integration dominates, resulting in a slower, mainly excitatory tRFs. At high contrast, tRFs are shorter and more strongly biphasic, similar to temporal derivatives. This adaptation emerges naturally from the non-linear probabilistic equations. Moreover, we found that bursts of spikes are preceded by strong inhibition while single spikes are not. We, next, use this model to investigate biophysical implementations of change detection and propose a specific neural mechanism based on synaptic short-term plasticity. We consider a small microcircuit commonly observed in many sensory areas, namely a pyramidal neuron receiving both mono-synaptic excitation from another pyramidal "source" cell and disynaptic inhibition from the same source cell. If the excitatory synapse is depressing and the inhibitory one facilitating, parameters of this biophysical system can be adjusted to approach the ideal performance. We compare this prediction with recent experimental data. Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: (2009). Is Sensory Processing about Detecting Abrupt Changes in the Sensory World?. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.351 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 10 Feb 2009; Published Online: 10 Feb 2009. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.