Current Principles of Motor Control, with Special Reference to Vertebrate Locomotion

Abstract

The vertebrate control of locomotion involves all levels of the nervous system from cortex to the spinal cord. Here, we aim to cover all main aspects of this complex behavior, from the operation of the microcircuits in the spinal cord to the systems and behavioral levels and extend from mammalian locomotion to the basic undulatory movements of lamprey and fish. The cellular basis of propulsion represents the core of the control system, and it involves the spinal central pattern generator networks (CPGs) controlling the timing of different muscles, the sensory compensation for perturbations, and the brain stem command systems controlling the level of activity of the CPGs and the speed of locomotion. The forebrain and in particular the basal ganglia are involved in determining which motor programs should be recruited at a given point of time and can both initiate and stop locomotor activity. The propulsive control system needs to be integrated with the postural control system to maintain body orientation. Moreover, the locomotor movements need to be steered so that the subject approaches the goal of the locomotor episode, or avoids colliding with elements in the environment or simply escapes at high speed. These different aspects will all be covered in the review.

Evaluating the Burstlet Theory of Inspiratory Rhythm and Pattern Generation

“…In general, network oscillators (distinct from pacemaker or inhibition-based models) rely on recurrent excitation among constituent rhythmogenic neurons (Grillner, 2006;Grillner and El Manira, 2020). Modifying the neuronal excitability influences the relative fraction of spontaneously active neurons in the network, and, for silent neurons, the proximity of baseline membrane potential to spike threshold.…”

Key role of 5‐HT1A receptors in the modulation of the neuronal network underlying the respiratory rhythm generation in lampreys

“…The general organization of the serotoninergic system in the lamprey is relatively well described and appears to share similarities with that of other vertebrates (Abalo et al, 2007;Antri, Cyr, Auclair, & Dubuc, 2006 for review see Grillner, 2006;Grillner & El Manira, 2019). In this control, mainly postsynaptic 5-HT 1A Rs appear to be involved (e.g.…”

Music Restores Propriospinal Excitation During Stroke Locomotion

“…In healthy subjects, TMS over the primary motor cortex inhibits the CPQ reflex during locomotion (Iglesias et al, 2008a), and the cortical contribution to quadriceps activity during walking is weak compared to a more volitional movement like an isolated tonic contraction of quadriceps (Iglesias et al, 2012). Thus, it has been suggested that the control of quadriceps during stabilized locomotion is likely subcortical in origin, and the propriospinal system plays a significant role in the transmission of the motor command to motoneurons, in line with the role of midbrain structures in the control of spinal locomotor central pattern generators (CPGs) in vertebrates (Grillner and El Manira, 2019). Alternatively, the role of proprioceptive feedback, especially muscle spindle group II afferents that are particularly active during TA lengthening contraction at the beginning of stance, has been raised (Marchand-Pauvert and Nielsen, 2002).…”

“…It has been well-established that listening to music and its practice induce remodeling of brain structures, with reorganization of neural networks in both healthy subjects and stroke patients (Altenmüller and Schlaug, 2015;O'Kelly et al, 2016). Regarding the spinal cord, which is particularly involved in the control of locomotion (Grillner and El Manira, 2019), the effect of sound on spinal activity has started to be explored at the beginning of the 20th century. In 1914, Forbes and Sherrington have observed a facilitating effect of sound on the Hoffmann (H) reflex in decerebrate cats (Barnes and Thomas, 1968).…”