Central Pattern Generators Mastication

Mastication is a vital function that ensures that ingested food is broken down into pieces and prepared for digestion. This review outlines the masticatory behavior in terms of the muscle activation patterns and jaw movements and gives an overview of the organization and function of the trigeminal neuronal circuits that are known to take part in the generation and control of oro-facial motor functions. The basic pattern of rhythmic jaw movements produced during mastication is generated by a Central Pattern Generator (CPG) located in the pons and medulla...

INTRODUCTION: The masticatory muscles are considered to be important determinants of facial form, but little is known of the muscle spindle reflex characteristics and their relationship, if any, to face height. The aim of this study was to determine whether spindle reflexes, evoked by mechanical stimulation of an incisor and recorded on the masseter muscle, correlated with different facial patterns. METHODS: Twenty-eight adult volunteers (16 women; ages, 19-38 years) underwent 2-N tap stimuli to their maxillary left central incisor during simulated mastication...

The main text of this chapter, written by James P. Lund, summarizes most of the work related to the neural control of mastication that he conducted with his collaborators throughout the years. From his early PhD work showing that mastication is centrally patterned to his latest work related to the interaction between pain and movement, Lund will have addressed many essential questions regarding the organization and functioning of the masticatory central pattern generator (CPG). His earliest studies examined how the CPG modulates reflexes and the excitability of primary afferents, interneurons, and motoneurons forming their circuitry...

The cellular and ionic mechanisms that generate the rhythm in central pattern generator (CPG) networks for simple movements are not well understood. Using vertebrate locomotion, respiration and mastication as exemplars, I describe four main principles of rhythmogenesis: (1) rhythmogenic ionic currents underlie all CPG networks, regardless of whether they are driven by a network pacemaker or an endogenous pacemaker neuron kernel; (2) fast synaptic transmission often evokes slow currents that can affect cycle frequency; (3) there are likely to be multiple and redundant mechanisms for rhythmogenesis in any essential CPG network; and (4) glial cells may participate in CPG network function...

Increasing evidence suggests that the dorsal part of the principal sensory nucleus of the trigeminal nerve (NVsnpr) contains a significant core of the central pattern generator (CPG) circuitry required for mastication (Tsuboi et al., 2003). Like many trigeminal brainstem neurons, those of NVsnpr are rhythmically active in phase with fictive mastication in vivo (Tsuboi et al., 2003) and project directly to the trigeminal motoneurons (Kolta et al., 2000), but in contrast with the others, they are the only neurons with intrinsic bursting abilities (Sandler et al...

Hypotheses regarding patterns of stress, strain and deformation in the craniofacial skeleton are central to adaptive explanations for the evolution of primate craniofacial form. The complexity of craniofacial skeletal morphology makes it difficult to evaluate these hypotheses with in vivo bone strain data. In this paper, new in vivo bone strain data from the intraorbital surfaces of the supraorbital torus, postorbital bar and postorbital septum, the anterior surface of the postorbital bar, and the anterior root of the zygoma are combined with published data from the supraorbital region and zygomatic arch to evaluate the validity of a finite-element model (FEM) of a macaque cranium during mastication...

Intra-oral prey processing (chewing) using the mandibular jaws occurs more extensively among teleost fishes than previously documented. The lack of muscle spindles, gamma-motoneurons and periodontal afferents in fishes makes them useful for testing hypotheses regarding the relationship between these sensorimotor components and rhythmic chewing in vertebrates. Electromyography (EMG) data from the adductor mandibulae (AM) were used to quantify variation in chew cycle duration in the bowfin Amia, three osteoglossomorphs (bony-tongues), four salmonids and one esocid (pike)...

Mastication can be triggered by repetitive stimulation of the cortex or of sensory inputs, but is patterned by a brain stem central pattern generator (CPG). This CPG may include the dorsal part of the principal trigeminal sensory nucleus (NVsnpr), where neurons burst repetitively when the extracellular concentration of Ca(2+) ([Ca(2+)](e)) drops. We examined the effects of repetitive stimulation of sensory afferents of the trigeminal tract on activity of NVsnpr neurons recorded extracellularly in vitro under physiologic [Ca(2+)](e) (1...

Trigeminal motoneurons (TMNs) relay the final output signals generated within the oral-motor pattern-generating circuits to the jaw muscles for execution of various patterns of motor activity. Activity-dependent plasticity, referred to as long-term potentiation (LTP), in the central nervous system has been the subject of many studies. The mechanisms of plasticity in the trigeminal system, an important component of the oral-motor system underlying mastication, swallowing, and other behaviors, remain to be fully elucidated...

BACKGROUND: The presence of the periodontal ligament (PDL) makes it possible to absorb and distribute loads produced during masticatory function and other tooth contacts into the alveolar process via the alveolar bone proper. However, several factors affect the integrity of periodontal structures causing the destruction of the connective matrix and cells, the loss of fibrous attachment, and the resorption of alveolar bone. METHODS: The purpose of this study was to evaluate the stress distribution by finite element analysis in a PDL in three-dimensional models of the upper central incisor under three different load conditions: 100 N occlusal loading at 45 degrees (model 1: masticatory load); 500 N at the incisal edge at 45 degrees (model 2: parafunctional habit); and 800 N at the buccal surface at 90 degrees (model 3: trauma case)...

PURPOSE OF REVIEW: Drinking and eating are essential skills for survival and benefit from the coordination of several pattern generating networks and their musculoskeletal effectors to achieve safe swallows. Oralpharyngoesophageal motility develops during infancy and early childhood, and is influenced by various factors, including neuromuscular maturation, dietary and postural habits, arousal state, ongoing illnesses, congenital anomalies, and the effects of medical or surgical interventions...

PURPOSE OF REVIEW: Feeding competency is a frequent and serious challenge to the neonatal intensive care unit survivors and to the physician-provider-parent teams. The urgency of effective assessment and intervention techniques is obviated to promote safe swallow, as attainment of oral feeding for the preterm infant/newborn is one of the prerequisites for hospital discharge. If left unresolved, feeding problems may persist into early childhood and may require management by pediatric gastroenterologists and feeding therapists...

In the central nervous system (CNS), central pattern generators (CPGs) are generally considered as specialized networks that can produce oscillatory motor output in the absence of any oscillatory input. For instance, respiration and mastication are among the critical biological functions well known to be controlled by such specialized networks. Several other CPGs have also been found specifically in the spinal cord. Among them, the CPG for locomotion is probably the most extensively studied rhythm- and pattern-generating network of the CNS...

Central pattern generators (CPGs) consisting of interacting groups of neurons drive a variety of repetitive, rhythmic behaviors in invertebrates and vertebrates, such as arise in locomotion, respiration, mastication, scratching, and so on. These CPGs are able to generate rhythmic activity in the absence of afferent feedback or rhythmic inputs. However, functionally relevant CPGs must adaptively respond to changing demands, manifested as changes in oscillation period or in relative phase durations in response to variations in non-patterned inputs or drives...

This tribute article to Professor James P. Lund stems from 6 of the presentations delivered at the July 1, 2008, symposium that honored 3 "giants" in orofacial neuroscience: B. J. Sessle, A. G. Hannam, and J. P. Lund. It was noted that soon after his training as a dentist in Australia, Jim Lund became interested in research. At the time he decided to do a PhD, there was a lot of discussion about how rhythmic movements were programmed. The early belief, based on Sherrington's studies of motor systems, was that these movements were simply an alternating series of reflexes...

Temporomandibular joint and masticatory muscle forces generated during bilateral biting on an experimental device simulating a symmetrically balanced maximum intercuspation, are unknown. The basic motor control strategies during such tasks, executed either strictly controlled or developed rather habitually, are also quite unclear. The main goal of this study was to compare muscle and joint forces at various magnitudes of force under two experimental conditions: (1) generation of a bite force vector perpendicular to the maxillary occlusal plane, (2) development of a directionally unrestricted (quasi-habitual) bite force, both with identical magnitude...

Based on its anatomical relationships, the lateral pterygoid muscle is strongly linked with the temporomandibular joint (TMJ). It plays a major role in mastication. Embryological, histological, and anatomical knowledge define the lateral pterygoid muscle as a single muscle with a penniform structure. The various results of electromyographic (EMG) studies describe a complex physiology with a chronological contraction of the layers during the masticatory cycle. The sequential contraction of the layers of the lateral pterygoid muscle is the result of a selective neuronal activation induced by the masticatory Central Pattern Generator (mCPG)...

The report describes oromandibular dystonia (OMD) in four women with involuntary activity of the lateral pterygoid muscles (LP), causing incapacitating protrusive and lateral jaw movements and displacements, and treatment with botulinum toxin type A (BTX). For initial survey and treatment control, OMD was analyzed with several, independent, and standardized methods. OMD severity and functional difficulties were evaluated subjectively and scored from videotapes. Jaw movements were assessed graphically with a magnetic tracking system, and electromyographical activity (EMG) of LP was recorded with needle electrodes using an intraoral approach, whereas activity of masseter muscles was recorded with surface electrodes...

Pyrokinin (PK) peptides localize to the central and peripheral nervous systems of arthropods, but their actions in the CNS have yet to be studied in any species. Here, we identify PK peptide family members in the crab Cancer borealis and characterize their actions on the gastric mill (chewing) and pyloric (filtering) motor circuits in the stomatogastric ganglion (STG). We identified PK-like immunolabeling in the STG neuropil, in projection neuron inputs to this ganglion, and in the neuroendocrine pericardial organs...

There is increasing evidence that a subpopulation of neurons in the dorsal principal sensory trigeminal nucleus are not simple sensory relays to the thalamus but may form the core of the central pattern generating circuits responsible for mastication. In this paper, we used whole cell patch recordings in brain stem slices of young rats to show that these neurons have intrinsic bursting abilities that persist in absence of extracellular Ca(2+). Application of different K(+) channel blockers affected duration and firing rate of bursts, but left bursting ability intact...