Sam Ling, Institute Junior Fellow, Gives April 20, 2016 Meet Our Fellows Talk

3:00 PM – 4:00 PM on Wednesday, April 20, 2016
Refreshments to follow
Hariri Institute for Computing
111 Cummington Mall, Room 180

The Formation & Flexibility of Visual Perception 

With an introduction given by Chantal Stern, Professor, Psychological & Brain Sciences and Director, Cognitive Neuroimaging Laboratory.

Sam Ling
Junior Faculty Fellow, Hariri Institute for Computing
Assistant Professor, Psychological & Brain Sciences, Center for Computational Neuroscience and Neural Technology

Abstract: While our ability to perceive the visual environment often seems effortless, the neural circuitry that gives rise to our percept remains something of a mystery. In this talk, I will describe human neuroimaging work aimed towards understanding how visual representations are formed, and how they can be altered to cater to our goals and needs. In the first half of the talk, I will focus on the neural mechanisms underlying a cornerstone of visual perception: orientation processing. Using machine learning approaches to data analyses, I will reveal evidence that orientation selectivity, a property believed to only exist in visual cortex, has subcortical origins, emerging as early as the human lateral geniculate nucleus (LGN). I will then show how these subcortical orientation representations elicit competitive interactions between each other, and their response patterns depend critically on attentional feedback. In the second half of the talk, I will describe neuroimaging work examining the neural computations underlying attentional modulation of visual responses.  Specifically, we investigate the hypothesis that visuocortical gain increases with attention rely on a release from local inhibition —a canonical neural computation. Using a novel voxel-wise analysis of visuocortical responses, we find evidence to suggest that the ability of a local neural subpopulation to increase its gain is critically dependent on its weighted normalization strength: local inhibition regulates a population’s potential for attentional benefits.

Bio: Sam Ling was selected as an Institute Junior Faculty Fellow in fall 2015. He is an assistant professor in Psychological and Brain Sciences at Boston University. Professor Ling directs the Visual Neuroscience lab, which aims to understand how the human visual system optimizes itself for the task at hand. Towards that end, his research combines a variety of techniques, including psychophysics, computational modeling, transcranial magnetic stimulation (TMS), and functional magnetic resonance imaging (fMRI) ­all aimed at understanding how early visual processing is formed, and how it can change as a result of top-down or bottom-up modulation. Prior to joining Boston University, Sam received his Ph.D. in psychology from New York University and completed his postdoctoral training at Vanderbilt University.