Secondary Somatosensory Cortex Is Required for Learning but Not Execution of a Tactile Discrimination

The relationship between primary (S1) and secondary (S2) somatosensory cortex is not well understood, and the role of S2 in somatosensory function is not well defined. To test the role of S2 and its interplay with S1 in learning a texture discrimination, we reversibly inhibited primary (S1) and/or secondary somatosensory cortex (S2) bilaterally using DREADDs and measured the effect on the ability of mice to learn a whisker-dependent tactile discrimination. Freely moving mice foraged in an arena that contained two bowls, one of which contained a buried food reward. The bowls could only be distinguished by the texture on the outer surface. DREADD-mediated inhibition suppressed sensory responses and disrupted network activity in the cortical area in which DREADDs were expressed. We found that both S1 and S2 were critical for learning the tactile discrimination. Tactile learning in naive mice required normal S2 function during the learning phase but not during the post-training consolidation phase of approximately 6 h. Furthermore, S2 was only required during learning. Once expert levels of discrimination had been attained, S2 was not required for execution of the learned discrimination. The role of S2 was confined to tactile learning and was not required for olfactory discrimination. Our findings suggest that S1 and S2 interact when learning a new tactile discrimination, but the learned skill eventually becomes independent of S2.