Sensory adaptation in the barrel cortex during active sensation in the awake, behaving mouse

Sensory adaptation (SA) is a prominent aspect of how neurons in anaesthetised animals respond to sensory signals, ubiquitous across species and modalities. However, SA depends on the activation state of the brain and it has been doubted whether SA is expressed in behaving animals. Here, we addressed this question by training mice to detect an object using their whiskers and recording neuronal activity from barrel cortex whilst simultaneously imaging the whiskers in 3D. We found that neuronal responses decreased during the course of whisker-object touch sequences but that this was due to two factors. First, a motor effect, whereby, during a sequence of touches, later touches were mechanically weaker than early ones. Second, a sensory encoding effect, whereby neuronal tuning to touch became progressively less sensitive during the course of a touch sequence. The sensory encoding effect was whisker-specific. These results show that SA does occur during active whisker sensing and suggest that SA is fundamental to sensation during natural behaviour.