Control of adaptive action selection by secondary motor cortex during flexible visual categorization

Adaptive action selection during stimulus categorization is an important feature of flexible behavior. To examine neural mechanism underlying this process, we trained mice to categorize the spatial frequencies of visual stimuli according to a boundary that changed between blocks of trials in a session. Using a model with a dynamic decision criterion, we found that sensory history was important for adaptive action selection after the switch of boundary. Bilateral inactivation of the secondary motor cortex (M2) impaired adaptive action selection by reducing the behavioral influence of sensory history. Electrophysiological recordings showed that M2 neurons carried more information about upcoming choice and previous sensory stimuli when sensorimotor association was being remapped than when it was stable. Thus, M2 causally contributes to flexible action selection during stimulus categorization, with the representations of upcoming choice and sensory history regulated by the demand to remap stimulus-action association.

Methods
Behavioral  experiments were controlled by custom Matlab (Mathworks) scripts and digital I/O devices (PCI-6503, National Instruments Corporation). Neural signals were amplified and filtered using the Cerebus 32-channel system (Blackrock Microsystems). Task-related behavioral events were digitized as TTL levels and recorded by the Cerebus system. Data analyses were performed in Matlab.