Timing precision in population coding of natural scenes in the early visual system

Abstract

Event Abstract Back to Event Timing precision in population coding of natural scenes in the early visual system The precision of neuronal spike trains is at the center of a fundamental debate in neuroscience as to what aspects of neuronal signaling are important in representing information in the brain. Individual neurons can have extremely precise and repeatable responses to the visual stimuli that strongly drive them (down to 1-ms variability), but they exhibit seemingly degraded temporal precision in response to suboptimal stimuli. In the presence of natural scenes, the activity of individual neurons is precisely timed across repeated presentations of the visual stimulus, even though natural stimuli tend to vary on a time scale that is several times slower. However, in most natural circumstances, the brain does not have access to multiple repetitions of the same identical stimulus, and, therefore, it is the precision of spiking across neuronal sub-populations on single trials that is ethologically relevant. While synchrony across neurons in the retina and visual cortex has been reported at various time scales, which can depend on the visual stimulus, the temporal precision of the neural code directly entering primary visual cortex, and its dependence on the stimulus, are still unknown. In this study (Desbordes et al., PLoS Biology, in press), we used natural visual stimuli to investigate spike timing precision in populations of geniculate neurons that serve as the direct input to visual cortex. A short movie of a natural scene recorded from a “cat-cam” (Kayser et al., 2003) was presented repeatedly to anesthetized cats while recording extracellular activity of multiple single units in the lateral geniculate nucleus (LGN) in vivo. To test how spike timing precision was affected by the properties of the visual stimulus, the same movie was presented both at high contrast and at low contrast. The absolute timing of firing events (or groups of closely spaced spikes) changed from trial to trial, and more so at low contrast than at high contrast, indicating that the response of individual neurons is less precise across stimulus repetitions when contrast is reduced. However, the relative timing of spikes occurring in the same trial was insensitive to changes in stimulus contrast - not only within cells but also across neighboring cells. At the population level, spike timing precision across LGN cells remained on the order of ~10 ms, irrespective of contrast. While it is well known that the response properties of single cells are strongly modulated by contrast adaptation, which has effects including slower temporal dynamics and increased gain and selectivity at lower contrast, our results indicate that the temporal precision of the LGN population code is globally maintained in the face of a reduction in contrast. Since closely timed spikes are more likely to induce a spike in the downstream cortical neuron to which they are projecting (Alonso et al., Nature, 1996), and since fine temporal precision is necessary in representing the more slowly varying natural environment (Butts et al., Nature, 2007), preserving the relative timing of spikes at a resolution of ~10 ms may be a crucial aspect of the neural code entering primary visual cortex. 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). Timing precision in population coding of natural scenes in the early visual system. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.325 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: 04 Feb 2009; Published Online: 04 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.