Correlated physiological and perceptual effects of noise in a tactile stimulus

Abstract

Event Abstract Back to Event Correlated physiological and perceptual effects of noise in a tactile stimulus Comparing neuronal firing parameters with the perceptual report for the same stimuli can be a powerful strategy for uncovering the brain's encoding and decoding mechanisms. The work reported here utilizes that strategy, but with the twist that the neuronal activity is recorded from the whisker-region of rat cortex (barrel cortex) while the perceptual report comes from human subjects. The stimuli in both cases are trains of skin deflections. If the predictions made from the barrel cortex data set are borne out in tests of human tactile perception, we can propose general coding principles that extend across species. We first investigated the responses of neurons in anesthetized rat barrel cortex to trains of whisker deflection, where each train had a periodic temporal structure but was characterized by either a constant-amplitude across all deflections or else variable amplitude (''amplitude noise''). Stimulus trains containing amplitude noise were matched with constant-amplitude trains for mean amplitude but included deflections smaller and larger than the mean. Cortical extracellular responses '' collected from the middle layers '' were equivalent for constant and noisy stimulus trains with frequencies up to 10 Hz. Above 10 Hz, amplitude noise led to a larger response magnitude as well as more prominent firing synchrony. The effects of amplitude noise are thus remarkably similar to those reported earlier for temporal noise: stimulus trains with an irregular sequence of interdeflection intervals evoke a larger and more synchronous cortical response than do frequency-matched periodic stimulus trains (Lak et al., Cerebral Cortex, 2008). The Romo laboratory has shown that in primates the perceived intensity of a train of deflections is correlated with somatosensory cortical firing rate. We predicted therefore that the presence of frequency and amplitude noise would increase response magnitude in human subjects, and that this would lead to an increase in perceived intensity, as compared to matched constant-amplitude or constant-frequency stimuli. We tested this prediction in a series of psychophysical experiments. For each subject, the threshold for detection of amplitude and frequency noise was estimated using a 2-interval forced choice (2AFC) noise detection task. A sub-threshold level of noise was used in the subsequent task. In a standard staircase procedure, subjects were asked to discriminate the intensity of pairs of vibrations delivered to their fingertip in a 2AFC paradigm in which one of the vibrations always had either amplitude or frequency noise while the other vibration did not. The key finding is that, although subjects were unaware of the noise, its presence still caused them to overestimate vibration intensity. Psychophysical effects were comparable '' in the magnitude and direction of perceptual bias '' with those predicted if the physiological effects of stimulus noise seen in barrel cortex were to generalize directly to humans. The main conclusions are that neurons in rat barrel cortex are ''tuned'' to respond in a different way to stimulus trains characterized by temporal and amplitude unpredictability, and that physiological phenomena from barrel cortex can be directly transferred to human tactile system to test hypotheses of perceptual mechanisms. 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). Correlated physiological and perceptual effects of noise in a tactile stimulus. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.278 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 Supplemental Data The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. 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