Touch-based object recognition relies on perception of compositional tactile features like roughness, shape, and surface orientation. However, besides roughness, it remains unclear how these different tactile features are encoded by neural activity that is linked with perception. Here, we establish a cortex-dependent perceptual task in which mice discriminate tactile gratings on the basis of orientation using only their whiskers. Multielectrode recordings in the barrel cortex reveal weak orientation tuning in average firing rates (500-ms time scale) during grating exploration despite high levels of cortical activity. Just before decision, orientation information extracted from fast cortical dynamics (100-ms time scale) more closely resembles concurrent psychophysical measurements than single neuron orientation tuning curves. This temporal code conveys both stimulus and choice/actionrelated information, suggesting that fast cortical dynamics during exploration of a tactile object both reflect the physical stimulus and affect the decision.
Rodents depend on olfaction and touch to meet many of their fundamental needs. The joint significance of these sensory systems is underscored by an intricate coupling between sniffing and whisking. However, the impact of simultaneous olfactory and tactile inputs on sensory representations in the cortex remains elusive. To study these interactions, we recorded large populations of barrel cortex neurons using 2-photon calcium imaging in head-fixed mice during olfactory and tactile stimulation. We find that odors alter barrel cortex activity in at least two ways, first by enhancing whisking, and second by central cross-talk that persists after whisking is abolished by facial nerve sectioning. Odors can either enhance or suppress barrel cortex neuronal responses, and while odor identity can be decoded from population activity, it does not interfere with the tactile representation. Thus, barrel cortex represents olfactory information which, in the absence of learned associations, is coded independently of tactile information.
Rodents depend on olfaction and touch to meet many of their fundamental needs. However, the impact of simultaneous olfactory and tactile inputs on sensory representations in the cortex remains elusive. To study these interactions, we recorded large populations of barrel cortex neurons using 2-photon calcium imaging in head-fixed mice during olfactory and tactile stimulation. Here we show that odors bidirectionally alter activity in a small but significant population of barrel cortex neurons through at least two mechanisms, first by enhancing whisking, and second by a central mechanism that persists after whisking is abolished by facial nerve sectioning. Odor responses have little impact on tactile information, and they are sufficient for decoding odor identity, while behavioral parameters like whisking, sniffing, and facial movements are not odor identity-specific. Thus, barrel cortex activity encodes specific olfactory information that is not linked with odor-induced changes in behavior.
Touch-based object recognition relies on perception of compositional tactile features like roughness, shape, and orientation. However, it remains unclear how the underlying spatio-temporal information from tactile sensors is integrated to form such percepts. Here, we establish a barrel cortex-dependent perceptual task in which mice use their whiskers to discriminate tactile gratings based on orientation. Multi-electrode recordings in barrel cortex during task performance reveal weak orientation tuning in the firing rate of single neurons during grating exploration despite high cortical firing rates. However, population-based classifiers decode grating orientation in line with concurrent psychophysical measurements and correlate with decisions on a trial-by-trial basis. For better decoding performance, the precise temporal sequence of population activity is necessary during grating exploration but becomes dispensable after decision. Our results suggest that temporal sequences of activity in barrel cortex carry orientation information during exploration. This code is reformatted around decision time to make firing rates more informative.
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