Circuits in the Ventral Medulla That Phase-Lock Motoneurons for Coordinated Sniffing and Whisking

Figure 2

Facial muscles involved in exploratory behavior in rodents. (a) The intrinsic muscles (Int) form a sling around the base of vibrissa follicles. When they contract, vibrissae protract. (b) Two groups of extrinsic muscles translate the mystacial pad: muscle nasolabialis (NL) and maxillolabialis (ML) retract the pad, while muscle nasolabialis profundus (NLP) protracts the pad. Extrinsic muscle fibers (mf) run underneath the skin between vibrissa rows. (c) Motoneurons that innervate the intrinsic vibrissa muscles are located in the ventral lateral part of the facial nucleus, the extrinsic retractor muscles (nasolabialis and maxillolabialis) are represented dorsolaterally, and the extrinsic protractor muscles (nasolabialis profundus) are represented at the lateral most edge of the nucleus. The drawings in (a) and (b) were adapted from Figure  11 of Grant et al. [15].

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