Activity in the rabbit somatosensory cortex reflects the active procedural memory trace of a classically conditioned eyeblink response.

Behavioral responses and neural responses in the somatosensory cortex were recorded in nine rabbits during the unpaired and paired treatments of classical eyeblink conditioning with a tone conditioned stimulus (CS) and an airpuff unconditioned stimulus. During the unpaired treatment, neither the behavioral nor neural responses to the CS were observed. During the paired treatment, behavioral conditioned response (CR), accompanied by neural activity, was developed. In well-trained animals occasional failures to elicit the CR were accompanied by an absence of neural responses. Nevertheless, the CS modified the behavioral unconditioned response in paired trials, implying that the CR-failures could not reflect the inability of the CS to modulate the pathways triggering the behavior constituting the CR. Thus, a close link between CR elicitation and somatosensory cortical neural response was established. Our finding suggests that this neural activity to a tone CS during classical eyeblink conditioning reflects an efferent copy of the procedural memory trace.