New modules are added to vibrissal premotor circuitry with the emergence of exploratory whisking.
Rodents begin to use bilaterally coordinated, rhythmic sweeping of their vibrissae ("whisking") for environmental exploration around 2 weeks after birth. Whether (and how) the vibrissal control circuitry changes after birth is unknown, and the relevant premotor circuitry remains poorly characterized. Using a modified rabies virus transsynaptic tracing strategy, we labeled neurons synapsing directly onto vibrissa facial motor neurons (vFMNs). Sources of potential excitatory, inhibitory, and modulatory vFMN premotor neurons, and differences between the premotor circuitry for vFMNs innervating intrinsic versus extrinsic vibrissal muscles were systematically characterized. The emergence of whisking is accompanied by the addition of new sets of bilateral excitatory inputs to vFMNs from neurons in the lateral paragigantocellularis (LPGi). Furthermore, descending axons from the motor cortex directly innervate LPGi premotor neurons. Thus, neural modules that are well suited to facilitate the bilateral coordination and cortical control of whisking are added to the premotor circuitry in parallel with the emergence of this exploratory behavior.
Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
Jun
J
Takatoh
Anders
A
Nelson
Xiang
X
Zhou
M McLean
MM
Bolton
Michael D
MD
Ehlers
Benjamin R
BR
Arenkiel
Richard
R
Mooney
Fan
F
Wang
D000818:Animals; D000831:Animals, Newborn; D005106:Exploratory Behavior / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009044:Motor Cortex / Q000254:growth & development*; D009415:Nerve Net / Q000254:growth & development*; D013003:Somatosensory Cortex / Q000254:growth & development*; D014738:Vibrissae / Q000254:growth & development*