How Does the Central Nervous System for Posture and Locomotion Cope With Damage-Induced Neural Asymmetry?

Abstract

In most vertebrates, posture and locomotion are achieved by a biomechanical apparatus whose effectors are symmetrically positioned around the main body axis. Logically, motor commands to these effectors are intrinsically adapted to such anatomical symmetry, and the underlying sensory-motor neural networks are correspondingly arranged during central nervous system (CNS) development. However, many developmental and/or life accidents may alter such neural organization and acutely generate asymmetries in motor operation that are often at least partially compensated for over time. First, we briefly present the basic sensory-motor organization of posturo-locomotor networks in vertebrates. Next, we review some aspects of neural plasticity that is implemented in response to unilateral central injury or asymmetrical sensory deprivation in order to substantially restore symmetry in the control of posturo-locomotor functions. Data are finally discussed in the context of CNS structure-function relationship.

A sensory signal related to left-right symmetry modulates intra- and interlimb cutaneous reflexes during locomotion in intact cats

“…Similar phase-dependent modulation was observed in all four limbs under varying levels of left-right asymmetry. From a clinical perspective, individuals with locomotor deficits resulting from spinal cord injury or stroke often show gait asymmetry (Wilmut et al, 2017;Le Ray and Guayasamin, 2022) accompanied by changes in stretch and cutaneous reflexes (Frigon et al, 2009;Zehr and Loadman, 2012). While split-belt locomotion can improve gait in such individuals, it may not benefit all (Reisman et al, 2010).…”

Perinatal development of central vestibular neurons in mice

“…Such an examination of the neurotransmitter phenotype of vestibular neurons is of particular relevance since a rebalancing of the synaptic actions of vestibular pathways contributes to so-called vestibular compensation, a form of neuronal plasticity that emerges in response to a vestibular dysfunction [( Precht et al, 1966 ; Smith and Curthoys, 1989 ; Ris et al, 1995 ; Ris and Godaux, 1998 ; Bergquist et al, 2008 ) and for reviews see ( Lambert and Straka, 2012 ; Le Ray and Guayasamin, 2022 )]. From a functional perspective also, it is noteworthy that at early developmental stages similar to those examined here, chloride-mediated synaptic signaling can exert excitatory rather than inhibitory influences due to an immature chloride gradient in brainstem neurons ( Ehrlich et al, 1999 ; Kakazu et al, 1999 ).…”

Effects of Occlusal Splints on Spinal Posture in Patients with Temporomandibular Disorders: A Systematic Review

“…Posture is comprehended as the position of the human body and its orientation in space [32,33]. It implicates neuro-muscular activation governed by the central nervous system, which permits postural adjustments as a result of a convoluted mechanical system stimulated by integrated, multisensory inputs [34][35][36]. Disturbances of this scenario are frequently observed in people who complain of dizziness, being one of the most common symptoms either in otologic or neurological clinics [35,37].…”