Control Pathways from the Subcortical Limbic Structures to the Trigeminal Motor System in the Lower Brainstem: A Hodological Review

Yukihiko Yasui

doi:10.4236/nm.2015.61005

Abstract

The organization of the emotion-related somatic motor behavior, including jaw movements, is governed not only by the cortical limbic system but also by the subcortical limbic system including the amygdala and hypothalamus. GABAergic neurons in the central amygdaloid nucleus (CeA) and glutamatergic neurons in the posterior lateral hypothalamus (PLH) exert inhibitory and excitatory influences, respectively, upon premotor neurons for the motor trigeminal nucleus (Vm) in the parvicellular reticular formation (RFp) of the medulla oblongata. The CeA also has an inhibitory influence on non-dopaminergic (probably GABAergic) neurons in the retrorubral field of the midbrain that send their axons to the RFp. Furthermore, the CeA and lateral hypothalamus including the PLH may also modulate Vm neurons via projections to the mesencephalic trigeminal nucleus which contains the cell bodies of primary afferent neurons conveying inputs from the masticatory muscle spindles or the periodontal ligament receptors to jaw closing motoneurons within the Vm. These pathways from the subcortical limbic structures to the trigeminal motor system in the lower brainstem underlie the regulation of emotional jaw movements.

Highlights

IntroductionJaw movements are carried out mainly by muscles attached to the mandibular bone, such as the masticatory and
Jaw movements are carried out mainly by muscles attached to the mandibular bone, such as the masticatory andHow to cite this paper: Yasui, Y. (2015) Control Pathways from the Subcortical Limbic Structures to the Trigeminal Motor System in the Lower Brainstem: A Hodological Review
After ipsilateral injections of biotinylated dextran amine (BDA) into theCeA and FG into the RFp, we demonstrated that the prominent overlapping distribution of BDA-labeled axon terminals and FG-labeled neurons was found in the lateral part of the RRF ipsilateral to the injection sites (Figure 3), where the BDA-labeled axon terminals made symmetrical synapses with somata and dendrites of the FG-labeled neurons [37]

Summary

Introduction

Jaw movements are carried out mainly by muscles attached to the mandibular bone, such as the masticatory and. The masticatory muscles as well as the mylohyoid muscle and anterior belly of the digastric muscle are innervated by motoneurons in the motor trigeminal nucleus (Vm). It is known that electrical stimulation of the hypothalamus induces attacks or defense responses in which opening and closing movement of jaws is one of the obvious elements [9]-[11]. In this communication, I summarize recent neuroanatomical and neurochemical studies on the control pathways to the Vm from the subcortical limbic structures, such as the amygdala and hypothalamus

Premotor Neuron Pools for Vm

Neuroanatomical Organization

Neurochemical Organization

Descending Pathways from the Hypothalamus to the Vm

Conclusion