The sensorimotor strategies and neuronal representations of tactile shape discrimination in mice

Humans and other animals can identify objects by active touch, requiring the coordination of exploratory motion and tactile sensation. The brain integrates movements with the resulting tactile signals to form a holistic representation of object identity. We developed a shape discrimination task that challenged head-fixed mice to discriminate concave from convex shapes. Behavioral decoding revealed that mice did this by comparing contacts across whiskers. In contrast, mice performing a shape detection task simply summed up contacts over whiskers. We recorded populations of neurons in the barrel cortex, which processes whisker input, to identify how it encoded the corresponding sensorimotor variables. Neurons across the cortical layers encoded touch, whisker motion, and task-related signals. Sensory representations were task-specific: during shape discrimination, neurons responded most robustly to behaviorally relevant whiskers, overriding somatotopy. We suggest a similar dynamic modulation may underlie object recognition in other brain areas and species.