Motor Function and ControlDescending Tracts
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
The motor cortex generates and controls motor commands, which are transmitted to the descending pyramidal and extrapyramidal tracts. The cerebral cortex consists of three reciprocally interconnected areas: primary motor cortex, supplementary motor cortex and premotor cortex (Figure 9.1). The primary motor cortex (Brodmann's area 4), located in the precentral sulcus, has a topographical representation of the body (motor homunculus) with the head, face and hands represented laterally and the legs and feet medially. The more complex the movement of a particular part of the body, the more motor cortex is devoted to it. The tongue, lips and hands have a much greater representation because of the complexity of their motor activity. The primary motor cortex is responsible for the control of voluntary movements.
Korbinian Brodmann (1868–1918)
Andrew P. Wickens in Key Thinkers in Neuroscience, 2018
The first results of this endeavour appeared in 1903 when Brodmann and Vogt presented their work at the annual meeting of the German Psychiatric Society in Jena. Here, Brodmann described the different cytoarchitectonic structure of the precentral and postcentral gyri in the human cerebral cortex. Today, we know these areas as the motor cortex and somatosensory cortex, respectively – the former being located in the posterior frontal lobe and involved in the wilful elicitation of movement, while the latter lying adjacent to the motor cortex (although separated by the central sulcus) in the anterior parietal cortex, which receives touch and proprioceptive feedback from the body. Brodmann’s work clearly revealed the structure, shape and position of the cells in these two regions to differ markedly – a finding supporting the idea that these two brain regions had very different behavioural functions.
The nervous system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Following the development of the motor program, neurons originating in the multimodal motor association areas transmit impulses by way of association tracts to the neurons of the primary motor cortex. The primary motor cortex is located within the precentral gyrus, which is the posterior-most region of the frontal lobe adjacent to the multimodal motor association areas (see Figure 6.3). It is this area that initiates voluntary contractions of specific skeletal muscles. Neurons whose cell bodies reside here transmit impulses by way of descending projection tracts to the spinal cord where they synapse with alpha motor neurons (which innervate skeletal muscles).
Cortical Networks for Correcting Errors in Sensorimotor Synchronization Depend on the Direction of Asynchrony
Published in Journal of Motor Behavior, 2018
K. J. Jantzen, Benjamin R. Ratcliff, McNeel G. Jantzen
Sensorimotor coordination is supported by a broad cortical and subcortical network that includes the primary motor cortex, lateral premotor cortex, basal ganglia, cerebellum, and motor regions of the mesial frontal cortex including the supplementary motor area (SMA) and anterior cingulate cortex (ACC; Jantzen & Kelso, 2007; Pollok, Gross, Müller, Aschersleben, & Schnitzler, 2005). There is growing evidence for a key role of some of these regions in detecting and correcting errors in coordination (Repp & Su, 2013a). In particular, the mesial motor areas including the SMA and anterior cingulate may play a role in maintaining patterns of sensorimotor synchronization. Neuroimaging studies consistently report activity in SMA during sensorimotor synchronization (Baumann et al., 2007; Gross et al., 2005; Jantzen & Kelso, 2007; Jantzen, Steinberg, & Kelso, 2009; Jantzen, Steinberg, Kelso, & Graybiel, 2004; Mayville, Jantzen, Fuchs, Steinberg, & Kelso, 2002; Pecenka, 2013). The SMA is involved in temporal processing and interval timing (Coull, Cheng, & Meck, 2011), making it a natural candidate for detecting and correcting timing errors. In keeping, activity in the SMA is greater for more complex and less stable movements (Ehrsson, Kuhtz-Buschbeck, & Forssberg, 2002; Mayville et al., 2002), which ostensibly place greater demands on error-correction processes, and correlates positively with variability in coordination suggesting an increase in activity as errors become larger and more frequent (Jantzen & Kelso, 2007).
Deficits underlying handgrip performance in mildly affected chronic stroke persons
Published in Topics in Stroke Rehabilitation, 2021
Esther Prados-Román, Irene Cabrera-Martos, Laura López-López, Janet Rodríguez-Torres, Irene Torres-Sánchez, Araceli Ortiz-Rubio, Marie Carmen Valenza
Jung et al.4 demonstrated that persons with weakness of the ipsilesional upper limb maximally recovered within 1-month poststroke but remained impaired in comparison with controls. Persistent impaired reaction time within the first year poststroke has been shown, indicating that ipsilesional upper limbs deficits might not be a temporary event.39,40 It has been shown that both the precision- and power-grip tasks activated the primary sensorimotor cortex contralateral to the grasping hand. The activations extended into the dorsal premotor cortex and the postcentral sulcus. Furthermore, the ventral premotor cortex showed bilateral activation with peaks of activity in the inferior part of the precentral gyrus.41 Among common assumptions motor deficits caused by disruption of ipsilesional projections of the corticospinal tract42 and changes in ipsilesional motor performance after nonaffected primary motor cortex disinhibition43 are included. However, little is known about the time course evolution of ipsilesional handgrip assessment, and even less about its implications for rehabilitation.40,44 Previous studies45,46 have reported difficulties in most clinical tests to detect fine changes in motor performance, specially the subtle ipsilesional motor deficits. Our study found significant differences on grip and pinch resistance to fatigue in the ipsilesional hand in comparison with controls. Moreover, significant differences were found on flexor digitorum superficialis muscle fatigue during a sustained handgrip contraction.
Peripheral somatosensory stimulation and postural recovery after stroke – a systematic review
Published in Topics in Stroke Rehabilitation, 2018
Jonas Schröder, Steven Truijen, Tamaya Van Criekinge, Wim Saeys
However, improved somatosensation after S1-stimulation showed only a small effect on motor functions50 and Kaelin-Lang et al.17 found increased motor cortex excitability after PSS without any change in S1 excitability. The authors consider short-term plastic changes in the motor cortex to be directly induced by afferent input, as the motor cortex receives somatotopically projections from the sensory cortex.17 Apparently, somatosensory input can drive not only somatosensory but also motor cortex excitability. Plastic changes in the motor cortex directly after PSS are probably responsible for immediate functional improvements.24,26,27,29,30 The immediate character of these effects seems to mimic those seen after rapid motor learning53 suggesting that afferent-induced changes in motor excitability is fundamental for learning.
Related Knowledge Centers
- Cerebral Cortex
- Posterior Parietal Cortex
- Premotor Cortex
- Primary Motor Cortex
- Supplementary Motor Area
- Frontal Lobe
- Primary Somatosensory Cortex
- Motor Control
- Precentral Gyrus
- Motor Planning