Sensory integration in PMd: position-dependent dynamic reweighting of vision and proprioception

Abstract

Event Abstract Back to Event Sensory integration in PMd: position-dependent dynamic reweighting of vision and proprioception Matthew Fellows1* and Phillip Sabes1 1 University of California San Francisco (UCSF), Department of Physiology and Keck Center , United States It has been observed behaviorally that human and non-human primates combine information from multiple sensory modalities. In many situations this combination has been found to be statistically near-optimal, meaning that the multi-modal (i.e., integrated) percept is formed by weighting each modality in proportion to its precision. However, sensory modalities are not represented homogeneously across cortex - for a given modality, both the strength of sensory representation and its functional role vary from area to area. How, then, do disparate local cortical representations manifest as globally optimal behavior? To begin addressing this question, we quantified – both behaviorally and in neurons – the integration of visual and proprioceptive information about hand location across a range of arm positions. We recorded simultaneous activity from large ensembles of dorsal premotor cortex (PMd) neurons in a monkey performing "out-to-center" reaching movements from multiple start locations to a central target, which he was required to fixate. We provided artificial visual feedback ("FB", a cursor) about the animal’s otherwise unseen hand location. This allowed us to impose a discrepancy ("FB shift") between the visual and proprioceptive feedback. We used FB shifts in different directions to measure how the animal weighted each modality when estimating hand location for reach planning. Optimality arguments predict that the integrated estimate of hand location should depend on the relative uncertainty of vision and proprioception. In general, these uncertainties are anisotropic and vary over space. That is, for hand localization, proprioceptive uncertainty changes with hand position, and visual uncertainty depends on hand position relative to gaze location. Therefore, due to the anisotropies, FB shifts in different directions should induce localization errors that differ in both magnitude and direction. In addition, due to the position-dependence, this pattern of shift-induced errors should change with start location. We quantified these error patterns both from the animal’s behavior and from population activity in PMd, and compared them. Behavioral analysis showed that the animal flexibly integrates vision and proprioception, with the weighting of each modality varying as a function of arm configuration: the observed error patterns showed systematic, position-dependent anisotropies. We observed flexible sensory reweighting in the PMd population activity as well, with error patterns that were similar to behavior in both orientation and position-dependence. However, the dependence on vision was greater for PMd than for behavior: for a given FB shift, the integrated hand location read-out from PMd is closer to the cursor than the location read-out from behavior. The spatial dependence we observed supports the idea that multi-modal integration, as measured with PMd activity and with behavior depends, at least in part, on the (anisotropic) variability of the sensory modalities. However, the greater dependence on vision in PMd suggests that sensory integration varies across the cortical reach circuit. For example, we expect that integration in primary motor cortex would look more like behavior than does PMd. This highlights the question of how diverse local cortical circuits are used in concert to drive overall behavior. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session I Citation: Fellows M and Sabes P (2010). Sensory integration in PMd: position-dependent dynamic reweighting of vision and proprioception. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00094 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: 20 Feb 2010; Published Online: 20 Feb 2010. * Correspondence: Matthew Fellows, University of California San Francisco (UCSF), Department of Physiology and Keck Center, Rijeka, United States, mrfellows@phy.ucsf.edu 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 Matthew Fellows Phillip Sabes Google Matthew Fellows Phillip Sabes Google Scholar Matthew Fellows Phillip Sabes PubMed Matthew Fellows Phillip Sabes 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.