Feedback in the brainstem: An excitatory disynaptic pathway for control of whisking

Abstract

Sensorimotor processing relies on hierarchical neuronal circuits to mediate sensory-driven behaviors. In the mouse vibrissa system, trigeminal brainstem circuits are thought to mediate the first stage of vibrissa scanning control via sensory feedback that provides reflexive protraction in response to stimulation. However, these circuits are not well defined. Here, we describe a complete disynaptic sensory receptor-to-muscle circuit for positive feedback in vibrissa movement. We identified a novel region of trigeminal brainstem, spinal trigeminal nucleus pars muralis, that contains a class of vGluT2+ excitatory projection neurons involved in vibrissa motor control. Complementary single- and duallabeling with traditional and virus tracers demonstrate that these neurons both receive primary inputs from vibrissa sensory afferent fibers and send monosynaptic connections to facial nucleus motoneurons that directly innervate vibrissa musculature. These anatomical results suggest a general role of disynaptic architecture in fast positive feedback for motor output driving active sensation.

Immunocytochemical organization and sour taste activation in the rostral nucleus of the solitary tract of mice

“…In particular, both of these atlases show the dorsomedial nucleus extending farther ventrally than does Astrom (). Importantly, CGRP‐immunoreactive nerve fibers of the trigeminal nerve extend only into the dorsal region as defined by Astrom (Sugimoto et al, ; Matthews et al, ) and as shown in the present work. Moreover, it is only this dorsal region that shows citric acid‐induced c‐Fos.…”

Parallel Inhibitory and Excitatory Trigemino-Facial Feedback Circuitry for Reflexive Vibrissa Movement

“…7). Further, a projection from the muralis division of the trigeminal sensory complex to the facial nucleus has been reported (Matthews et al, 2015). This projection was proposed to be part of a reflex pathway.…”

The Brainstem Oscillator for Whisking and the Case for Breathing as the Master Clock for Orofacial Motor Actions

“…8D). One possible explanation for how these signals may influence facial motoneurons, under current investigation, is that they act as commands that are relayed through trigeminal nuclei (Matthews et al 2015) that further project to facial motor neurons (Pinganaud et al 1999). It will be valuable to determine if similar neuronal coding applies to the cortical control of other orofacial actions (Sawczuk and Mosier 2001).…”

“…One possibility is that rapid whisking is generated by a disynaptic feedback loop in the brainstem (Nguyen and Kleinfeld 2005; Deutsch et al 2012; Matthews et al 2015). That is, sensory signals generated by the motion of the vibrissa could drive the facial motoneurons, which in turn would regenerate a sensory signal, and so on.…”