Motor control of the Wet dog shake behavior in rats.

Abstract

Introduction: Wet dog shake (WDS) is a motion in mammals and birds, consisting in vigorous and rapid rotations of the head and trunk around the spinal axis, which allows them to dry themselves. WDS requires fine balance control. To date, motor control in WDS has not been studied.

Methods: Here, for the first time, we investigated the trunk and limbs muscle EMG activity and correlated it with the kinematics of body movement and ground reactions force during WDS in rats.

Results: Strict reciprocity was revealed between the forelimb muscle on the right and left sides despite bipedal hindlimb position. Reciprocal activity was observed between the lumbar and the thoracic segments. The hindlimb muscle activity exhibited two distinct muscle synergies with strict reciprocity and atypical co-activity of flexors and extensors, which were previously observed in paw shaking behavior. These two synergies correlate with the two muscle groups of the pelvic fins of fish. The absence of typical postural responses of the hindlimb was revealed.

Conclusions: 1) It is likely that WDS and paw shaking share a common nervous control. 2) The absence of typical postural responses may indicate that body balance in WDS is maintained by perfectly matched frequency and strength of the trunk muscle contractions. 3) In the hypothesis about the origin of WDS, based on the revealed characteristics, we compare it with the S-start response behavior in fish.