Contextual control of trigeminal sensorimotor function.

Simple actions, such as rhythmic tongue protrusions, forelimb facial strokes, and forelimb flails, are emitted by rats both during taste-elicited ingestion/aversion and during postprandial grooming. This study combined peripheral trigeminal deafferentation with a computer-assisted video analysis of action form to examine the use of cutaneous feedback from the face in action production. Changes in action form after deafferentation were found to be context-dependent: Deformations characterized rhythmic tongue protrusions when emitted in ingestive but not in grooming contexts. The opposite was true for alterations in forelimb action. Further, postprandial grooming as a whole was found to comprise distinct sequentially defined phases. Actions occurring in one highly stereotyped sequence phase were protected from deafferentation effects, although the same actions occurring outside of this phase were not. The results suggest that behavioral context (e.g., grooming versus ingestive set, sequence phase) can shift the integration of sensory guided and endogenous mechanisms that pattern simple actions.