Encoding and decoding cortical representations of tactile features in the vibrissa system

Abstract

During behavior, rats and other rodents use their facial vibrissae to actively explore surfaces through whisking and head/body movement, resulting in complex sensory inputs that vary over a large range of angular velocities and temporal scales. How these complex sensory inputs manifest in the patterns of cortical firing events that ultimately form the perceptual experience is not well understood. Through single-unit cortical recordings of layer 4 neurons in S1 of the anesthetized rat, we systematically quantified the interactions between instantaneous velocity andtiming of vibrissa motion, finding a strong interactionbetweenangular velocityandtiming of contactsonthe tens of milliseconds time scale. Fromthe quantification of these joint tuning properties, a detailed nonlinear encodingmodelwasformulated thatwashighly predictive of firing probability and timing characteristics of the sparse cortical representation of complex patterned tactile inputs. Within a Bayesian framework, the encoding model was then used to decode tactile patterns under simple transformations of the stimulus along dimensions of velocity and timing, as a demonstration of the lower bound of the idealized perceptual capabilities of the animal. Copyright © 2010 the authors.