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S. E. Boehnke, D. J. Berg, K. Kaneda, Y. Yanagawa, L. Itti, T. Isa, D. P. Munoz, Temporal characteristics and mechanisms of visual adaptation in the superior colliculus, In: Proc. Society for Neuroscience Annual Meeting (SFN'09), Oct 2009.
Abstract: Repeated visual stimulation leads to reduced sensory responsiveness (adaptation) in neurons across the visual system. Adaptation of visual responses also occurs in superior colliculus neurons following repeated stimulation, and it has the behavioral consequence of delayed visual orienting. It is currently unknown which temporal characteristics of repeating stimuli affect the degree of adaptation in SC visual neurons (stimulus duration, onset-onset time or offset-onset time) and it remains unclear if adaptation in the SC is the result of an intrinsic mechanism or simply inherited through adapted inputs. We addressed these issues by comparing adaptation of SC superficial (SCS) neurons in behaving monkeys and in the mouse slice preparation, following sequences of four repetitive visual stimuli (flashes and electrical microstimulation of visual afferents to the SCS, respectively) that varied in several temporal parameters. The degree of adaptation across temporal configurations were remarkable similar between awake monkey neurons and mouse slice neurons. Neurons recorded from the SCS layers in both monkey and slice responded transiently or in a sustained fashion, with transient responders showing greater adaptation than sustained responders. Adaptation was generally characterized by a decrease in onset firing rate and an increase in visual response onset latency. The amount of adaptation was dependent to varying degrees on both the duration of the stimulus and the time between stimuli (longer recovery time reducing adaptation). Although these factors interacted in a complex way, a simple Bayesian model (Surprise) which takes stimulus history at several time scales into account could well explain the patterns of adaptation observed across temporal configurations. In non-GABAergic neurons, identified by lack of GFP fluorescence in GAD67-GFP knock-in mice, adaptation was examined before and after bath application of GABAB blocker (CGP52432). GABAB blockage significantly reduced the amount of adaptation observed (p<0.05), suggesting that at least part of the adaptation is caused by an intrinsic mechanism in the SCS circuitry. These data are important for understanding visual temporal processing in general, and guiding stimulus design and interpretation of results from studies in visual/cognitive neuroscience in which sequences of stimuli are presented.
Themes: Computational Modeling, Monkey Electrophysiology, Bayesian Theory of Surprise
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