Deafferentation does not disrupt natural rules of action syntax.

Natural rules of action syntax control the sequential order of grooming and ingestive/aversive actions emitted by rats. Grooming and ingestive actions share a common feature in that all are performed with or directed towards the mouth, tongue, and face. This study examined the role of orofacial somatosensory cues and feedback in the generation of natural action syntax. Bilateral deafferentation of the mandibular and maxillary branches of the trigeminal nerve was used to eliminate tactile sensation from the rostral face and mouth while preserving motor function. Neither the overall degree of sequential stereotypy (H) of grooming or ingestive sequences, nor the generation of particular natural sequencing rules were affected by trigeminal deafferentation. These natural rules appear to be specified by the brain without need of somatosensory feedback.