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.
Nervous system
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
The next region of the frontal lobe is the primary motor cortex situated directly in front of the central sulcus that separates the frontal lobe from the parietal lobe (Figure 12.10). It generates nerve impulses that activate skeletal muscle and control the execution of movement on the opposite (contralateral) side of the body. The primary motor cortex is mapped so that specific areas control the movement of particular body parts. For example, foot and leg movements map to the part of the primary motor cortex closest to the midline. Parts of the body capable of a high degree of movement, such as the hands and lips, are represented by large areas of the primary motor cortex. The premotor cortex consists of a narrow strip of tissue situated between the prefrontal and primary motor cortices. It helps to anticipate and plan voluntary movement and controls learned motor skills necessary to play a musical instrument or type. It also seems to play a role in the initiation and onset of laughter in response to others laughing.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
As with the other lobes of the brain, within the frontal lobes are areas of primary, secondary and association cortex. In the human brain, primary motor cortex is anterior to the central sulcus in the PRECENTRAL GYRUS. Secondary motor cortex (PREMOTOR CORTEX, SUPPLEMENTARY MOTOR GORTEX) occupies the cortex adjacent and rostral to primary motor cortex. The most anterior and the largest portion of the human frontal lobe is higher-order association cortex (PREFRONTAL CORTEX and LIMBIC CORTEX), which can be divided into many functionally distinct sub-regions and includes, for example, BROCA'S AREA. LIMBIC ASSOCIATION CORTEX, which includes ORBITOFRONTAL CORTEX, occupies the ventral and medial aspect of the frontal lobe, but also extends to other cortical lobes, all of which is sometimes referred to collectively as the LIMBIC LOBE. However, as the definition of the four cortical lobes is based on structural landmarks, in contrast to the definition of the limbic lobe, which is based on connectivity and function, it is not, strictly speaking, equivalent to a lobe. There is a hierarchical organization of projections within the frontal lobe, with prefrontal and limbic association areas receiving projections from areas of sensory association cortex in the other lobes. Limbic association cortex projects to prefrontal cortex, which projects to secondary motor cortex, which in turn projects to primary motor cortex.
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
We identified 6 active cortical sources (Figure 2). Two sources localized to the primary motor cortex. An anterior source (SMCa) on the postcentral gyrus and the anterior wall of the central sulcus was localized to Brodmann areas (BAs) 4 and 6. A posterior motor cortex source (SMCp) on the posterior bank of the central sulcus localized to BAs 3 and 4. Although these two regions combined at lower thresholds, and therefore may represent a single motor source, they displayed distinct peaks prompting us to analyze their activity separately. A dorsal medial source in BA 6 was localized almost entirely anterior to the vertical anterior commissure line in keeping with the anatomical location of the pre-SMA (Kim et al., 2010; Picard & Strick, 1996). We also identified two regions on the cingulate cortex. The first was in the ACC extending across BAs 24 and 32 and the second was in the posterior cingulate located in BA 31. A final active region was localized to the contralateral posterior parietal cortex extending into BAs 3, 7, and 40. The Talairach coordinates, anatomical location and size of each region of interest is provided in (Table 1).
Transcranial Direct Current Stimulation of Motor Cortex Enhances Spike Performances of Professional Female Volleyball Players
Published in Journal of Motor Behavior, 2023
Seung-Bo Park, Doug Hyun Han, Junggi Hong, Jea-Woog Lee
In female volleyball competitions, high skill levels and general motor coordination are undoubtedly performance-related elements that can impact success (Pion et al., 2015). Stamm et al. (2005) have found that fundamental volleyball abilities such as spiking, blocking, and feinting are associated with success of volleyball players. In this regard, the primary motor cortex (M1) is an essential region for motor coordination and functions in terms of speed, endurance, strength, precision, and execution of motor tasks (Levasseur-Moreau et al., 2013). This cortical region is a complex network that interconnects localized groups of neurons with similar input and output processes to control arm and leg movements (Huang et al., 2019; Schieber, 2001). The M1 is responsible for the production of neural impulses that regulate movement execution (Huang et al., 2019; Moscatelli et al., 2016). It is thought that these networks can control the induction of plasticity. Their sensitivity to exercise-induced manipulation is of special interest (Singh & Staines, 2015). Various connections of the M1 that react and adapt to external stimuli appear to be highly plastic (Moscatelli et al., 2021). Several studies have reported that increased excitability of the M1 region can increase exercise performance (Wang et al., 2021).
Review of “The Central Nervous System, 5th Edition,” by Per Brodal
Published in The Neurodiagnostic Journal, 2018
Readers may wonder how information in this book can guide the average practitioner of neurophysiology. Aside from the clinical pearls that supplement the material throughout, the book is packed with information critical to maximizing your clinical practice. Here’s an example: As we are all aware, many surgeons working near eloquent cortical regions will perform SSEP phase reversal to identify the central sulcus and then begin resection of tumor/tissue without ever mapping motor cortex. I think we can all agree that it’s best practice to map motor cortex whenever possible, but how do you convince a surgeon to do it? A reading of Chapter 22, “The Motor Cortical Areas and Descending Pathways,” informs the reader that only about one third of corticospinal tract cells originate in the “primary motor cortex” (i.e., the precentral gyrus). The other two thirds come from the primary somatosensory cortex” (i.e., postcentral gyrus), as well as the premotor and supplementary motor areas of the frontal lobes. Armed with this type of knowledge, the savvy neurophysiologist has a strong argument for using direct electrical stimulation of cortex (i.e., motor mapping) in addition to phase reversal to rule out regions that may contain critical motor neurons. This can certainly increase the safety of brain surgery and improve clinical outcomes.