Event Abstract Back to Event Inhibition facilitates fast, robust motion detection in the visual cortex A classical question of computational and systems neuroscience addresses the mechanism underlying direction selectivity of simple cells of primary visual cortex. In a prominent class of models, a cortical cell integrates excitatory inputs of different response latencies and offset receptive field positions arranged such that inputs arrive synchronously for stimuli moving in the preferred direction, but dispersed in time for stimuli in the null direction. Selectivity is assumed to be sharpened by a spike threshold. Here we probe this mechanism quantitatively: in particular, in the presence of an additional noisy input (due to, for example, random background activity), which is known to affect the threshold nonlinearity of the input-output relationship. Furthermore, we explore a possible role for inhibition, which has been found to be tuned for the same direction as excitation, but with different relative timing (Priebe and Ferster, 2005). We implement this model based on an exponential integrate-and-fire neuron (Fourcaud-Trocme et al., 2003). We model the noisy input by i) an additional noise current and/or ii) different degrees of spontaneous activity of input neurons. Our basic results are captured also by a simple rate model. We find that if only excitatory inputs are present, small levels of noisy input reduce direction selectivity strongly. For large noise, the mean firing rate for both stimulus directions is approximately equal, resulting in a very weakly selective neuron. In this regime, the firing rate is approximately proportional to input strength. Since the total number of inputs is the same for both directions (only their temporal order differs) the mean firing rate is approximately equal for both directions. In contrast, when inhibitory inputs are included and arranged in a push-pull fashion, as observed by Priebe and Ferster (2005), selectivity is fully recovered even for large levels of noise. For the null direction, both excitatory and inhibitory inputs arrive dispersed in time and therefore largely cancel each other resulting in a firing rate close to baseline. For the preferred direction, excitatory and inhibitory inputs each arrive synchronously, but with a temporal lag relative to each other. Since firing rate is bounded by zero, the increase in firing rate due to the excitatory inputs can greatly exceed the decrease caused by the inhibitory inputs, resulting in a strongly direction selective neuron. A similar result holds when probing the neuron with a drifting grating and defining selectivity based on the first Fourier component of firing rates during a stimulus period. Interestingly, in the presence of inhibition, the neuron responds selectively even after one stimulus cycle (~100ms) for various levels of noise. We conclude that inhibition in a push-pull organization is an essential part of the mechanism underlying cortical direction selectivity, providing robust selective responses in the presence of noisy or unrelated background activity, even after brief stimulus presentations. 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). Inhibition facilitates fast, robust motion detection in the visual cortex. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.149 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: 02 Feb 2009; Published Online: 02 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.