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Current Opinion in Neurobiology Apr 2018Neurons in motor cortex and connected brain regions fire in anticipation of specific movements, long before movement occurs. This neural activity reflects internal... (Review)
Review
Neurons in motor cortex and connected brain regions fire in anticipation of specific movements, long before movement occurs. This neural activity reflects internal processes by which the brain plans and executes volitional movements. The study of motor planning offers an opportunity to understand how the structure and dynamics of neural circuits support persistent internal states and how these states influence behavior. Recent advances in large-scale neural recordings are beginning to decipher the relationship of the dynamics of populations of neurons during motor planning and movements. New behavioral tasks in rodents, together with quantified perturbations, link dynamics in specific nodes of neural circuits to behavior. These studies reveal a neural network distributed across multiple brain regions that collectively supports motor planning. We review recent advances and highlight areas where further work is needed to achieve a deeper understanding of the mechanisms underlying motor planning and related cognitive processes.
Topics: Animals; Executive Function; Humans; Motor Cortex; Movement; Neural Pathways; Neurons; Psychomotor Performance
PubMed: 29172091
DOI: 10.1016/j.conb.2017.10.023 -
Neurosurgical Focus Sep 2001In 1991 Tsubokawa and colleagues first published their landmark results from a series in which epidural motor cortex stimulation (MCS) was used in the treatment of eight... (Review)
Review
In 1991 Tsubokawa and colleagues first published their landmark results from a series in which epidural motor cortex stimulation (MCS) was used in the treatment of eight patients with central and neuropathic pain. In ensuing studies authors have elaborated on the indications, technique, hypotheical mechanisms, and beneficial results of this treatment. Epidural MCS is effective for trigeminal neuropathy, lateral medullary and thalamic infarction, anesthesia dolorosa, postherpetic neuralgia, spinal cord injury, and limb stump pain. Postoperative outcomes are better when patients present with only mild or absent motor weakness in the region of pain and when there is pain in the trigeminal region. It is hypothesized that MCS is effective because it increases regional cerebral blood flow in the ipsilateral ventrolateral thalamus in which corticothalamic connections from the motor and premotor areas predominate. The extent of pain alleviation also correlates with the increase of blood flow in the cingulate gyrus. This suggests that stimulation reduces the suffering experienced by a patient with chronic pain. Procedure-related morbidity has included epidural hematoma, subdural effusion, gradual diminution of benefit, and painful stimulation. Although of concern, treatment-induced chronic seizure disorders have not occurred as a complication or in animal models of chronic cortical stimulation. Stimulation-induced pain relief occurs within minutes. There are no associated paresthesias or muscle contractions that confirm function. Pain relief may last for hours after electrical stimulation is discontinued. Motor cortex stimulation is an established therapy for the treatment of complex central and neuropathic pain syndromes that have proved refractory to medical treatment.
Topics: Electric Stimulation Therapy; Humans; Motor Cortex; Pain Management
PubMed: 16519425
DOI: No ID Found -
Nature Reviews. Neuroscience Aug 2020The human motor cortex comprises a microcircuit of five interconnected layers with different cell types. In this Review, we use a layer-specific and cell-specific... (Review)
Review
The human motor cortex comprises a microcircuit of five interconnected layers with different cell types. In this Review, we use a layer-specific and cell-specific approach to integrate physiological accounts of this motor cortex microcircuit with the pathophysiology of neurodegenerative diseases affecting motor functions. In doing so we can begin to link motor microcircuit pathology to specific disease stages and clinical phenotypes. Based on microcircuit physiology, we can make future predictions of axonal loss and microcircuit dysfunction. With recent advances in high-resolution neuroimaging we can then test these predictions in humans in vivo, providing mechanistic insights into neurodegenerative disease.
Topics: Animals; Humans; Motor Cortex; Neural Pathways; Neurodegenerative Diseases
PubMed: 32555340
DOI: 10.1038/s41583-020-0315-1 -
Current Opinion in Neurobiology Aug 2015The issue of coding of movement in the motor cortex has recently acquired special significance due to its fundamental importance in neuroprosthetic applications. The... (Review)
Review
The issue of coding of movement in the motor cortex has recently acquired special significance due to its fundamental importance in neuroprosthetic applications. The challenge of controlling a prosthetic arm by processed motor cortical activity has opened a new era of research in applied medicine but has also provided an 'acid test' for hypotheses regarding coding of movement in the motor cortex. The successful decoding of movement information from the activity of motor cortical cells using their directional tuning and population coding has propelled successful neuroprosthetic applications and, at the same time, asserted the utility of those early discoveries, dating back to the early 1980s.
Topics: Afferent Pathways; Hand Strength; Humans; Models, Biological; Motor Cortex; Movement; Neurons
PubMed: 25646932
DOI: 10.1016/j.conb.2015.01.012 -
Current Opinion in Neurobiology Oct 2014Our ability to learn and control the motor aspects of complex laryngeal behaviors, such as speech and song, is modulated by the laryngeal motor cortex (LMC), which is... (Review)
Review
Our ability to learn and control the motor aspects of complex laryngeal behaviors, such as speech and song, is modulated by the laryngeal motor cortex (LMC), which is situated in the area 4 of the primary motor cortex and establishes both direct and indirect connections with laryngeal motoneurons. In contrast, the LMC in monkeys is located in the area 6 of the premotor cortex, projects only indirectly to laryngeal motoneurons and its destruction has essentially no effect on production of species-specific calls. These differences in cytoarchitectonic location and connectivity may be a result of hominid evolution that led to the LMC shift from the phylogenetically 'old' to 'new' motor cortex in order to fulfill its paramount function, that is, voluntary motor control of human speech and song production.
Topics: Brain Mapping; Humans; Larynx; Motor Cortex; Motor Neurons; Neural Pathways
PubMed: 24929930
DOI: 10.1016/j.conb.2014.05.006 -
Neuroscience and Biobehavioral Reviews Sep 2017In recent years, sheep (Ovis aries) have emerged as a useful animal model for neurological research due to their relatively large brain and blood vessel size, their... (Review)
Review
In recent years, sheep (Ovis aries) have emerged as a useful animal model for neurological research due to their relatively large brain and blood vessel size, their cortical architecture, and their docile temperament. However, the functional anatomy of sheep brain is not as well studied as that of non-human primates, rodents, and felines. For example, while the location of the sheep motor cortex has been known for many years, there have been few studies of the somatotopy of the motor cortex and there were a range of discrepancies across them. The motivation for this review is to provide a definitive resource for studies of the sheep motor cortex. This work critically reviews the literature examining the organization of the motor cortex in sheep, utilizing studies that have applied direct electrical stimulation and histological methods A clearer understanding of the sheep brain will facilitate and progress the use of this species as a scientific animal model for neurological research.
Topics: Animals; Brain Mapping; Motor Cortex; Neurons; Sheep
PubMed: 28595827
DOI: 10.1016/j.neubiorev.2017.06.002 -
The Journal of Neuroscience : the... Oct 2018In the 1960s, Evarts first recorded the activity of single neurons in motor cortex of behaving monkeys (Evarts, 1968). In the 50 years since, great effort has been... (Review)
Review
In the 1960s, Evarts first recorded the activity of single neurons in motor cortex of behaving monkeys (Evarts, 1968). In the 50 years since, great effort has been devoted to understanding how single neuron activity relates to movement. Yet these single neurons exist within a vast network, the nature of which has been largely inaccessible. With advances in recording technologies, algorithms, and computational power, the ability to study these networks is increasing exponentially. Recent experimental results suggest that the dynamical properties of these networks are critical to movement planning and execution. Here we discuss this dynamical systems perspective and how it is reshaping our understanding of the motor cortices. Following an overview of key studies in motor cortex, we discuss techniques to uncover the "latent factors" underlying observed neural population activity. Finally, we discuss efforts to use these factors to improve the performance of brain-machine interfaces, promising to make these findings broadly relevant to neuroengineering as well as systems neuroscience.
Topics: Animals; Brain-Computer Interfaces; Humans; Motor Cortex; Movement; Neurons; Time Factors
PubMed: 30381431
DOI: 10.1523/JNEUROSCI.1669-18.2018 -
Neuroscience and Biobehavioral Reviews Dec 2013This review examines the involvement of the motor cortex in Parkinson's disease (PD), a debilitating movement disorder typified by degeneration of dopamine cells of the... (Review)
Review
This review examines the involvement of the motor cortex in Parkinson's disease (PD), a debilitating movement disorder typified by degeneration of dopamine cells of the substantia nigra. While much of PD research has focused on the caudate/putamen, many aspects of motor cortex function are abnormal in PD patients and in animal models of PD, implicating motor cortex involvement in disease symptoms and their treatment. Herein, we discuss several lines of evidence to support this hypothesis. Dopamine depletion alters regional metabolism in the motor cortex and also reduces interneuron activity, causing a breakdown in intracortical inhibition. This leads to functional reorganization of motor maps and excessive corticostriatal synchrony when movement is initiated. Recent work suggests that electrical stimulation of the motor cortex provides a clinical benefit for PD patients. Based on extant research, we identify a number of unanswered questions regarding the motor cortex in PD and argue that a better understanding of the contribution of the motor cortex to PD symptoms will facilitate the development of novel therapeutic approaches.
Topics: Deep Brain Stimulation; Dopamine; Humans; Motor Cortex; Parkinson Disease
PubMed: 24113323
DOI: 10.1016/j.neubiorev.2013.09.008 -
European Neurology 1996Traditionally, the SMA has been defined as a single motor area in the medial part of the frontal agranular cortex. Recent anatomical and physiological studies, however,... (Review)
Review
Traditionally, the SMA has been defined as a single motor area in the medial part of the frontal agranular cortex. Recent anatomical and physiological studies, however, defined two areas in the medial part of Brodmann's area 6. The anterior part is now called the presupplementary motor area (pre-SMA) and the posterior part, the SMA proper or the SMA. Both areas have unique combinations of cortical and thalamocortical connectivity. Although neurons in both areas take some part in simple motor tasks such as pushing buttons in response to sensory signals, characteristic activity is found in the kind of motor tasks that require temporal organization. Temporal sequencing of multiple movements, for instance, requires a role of neuronal activity in both the SMA and pre-SMA.
Topics: Brain Mapping; Functional Laterality; Humans; Motor Cortex; Movement; Neurons
PubMed: 8791016
DOI: 10.1159/000118878 -
The Neurologist Sep 2004For more than a century, unusual and complex deficits in facial expression have been known to occur following localized brain damage. Some brain injuries leave the face... (Review)
Review
BACKGROUND
For more than a century, unusual and complex deficits in facial expression have been known to occur following localized brain damage. Some brain injuries leave the face with pronounced alterations in affect whereas others result in movement disorders such as blepharospasm and Meige syndrome. There is also a historic trail of clinical observations that document deficits in either voluntary or emotional control of the facial muscles following central nervous system damage.
REVIEW SUMMARY
Recent studies in the nonhuman primate cerebral cortex reveal the existence of multiple cortical facial representations in the frontal lobe and adjacent anterior cingulate cortex. These comprise the facial representation of the primary motor cortex (M1), ventral lateral premotor cortex (LPMCv), supplementary motor cortex (M2), rostral cingulate motor cortex (M3), and caudal cingulate motor cortex (M4). Homologous facial representations reside in the human brain based on observations following cortical stimulation, functional neuroimaging, and localized surgical resection. In the nonhuman primate, all these facial representations have been found to be directly interconnected through topographically organized corticocortical connections, and each facial area has also been found to send direct corticobulbar projections to the facial motor nucleus. The facial representations of M2 and M3 are both located on the medial wall of the hemisphere, in the vascular territory of the anterior cerebral artery. Both preferentially give rise to bilateral projections to parts of the facial nucleus that innervate the upper facial musculature as demonstrated in the monkey. The facial representation of M1, LPMCv, and M4 preferentially give rise to contralateral axonal projections ending in parts of the facial nucleus that innervate the lower facial musculature. The facial representation of M1 and LPMCv both reside in the vascular territory of the middle cerebral artery (MCA). The classic clinical presentation of paralysis in the contralateral lower facial musculature and intact bilateral upper facial musculature following typical MCA in infarction in the human parallels this mapping pattern of corticobulbar connections found in the nonhuman primate.
CONCLUSIONS
Facial movements are undoubtedly under the powerful influence of the cerebral cortex and are essential for the appropriate execution of many important functions such as mastication, swallowing, and social interaction, including speech and nonverbal communication. This information provides a theoretic template for interpreting the clinical effects of neuropathologic disease and localized cortical trauma on facial movements.
Topics: Animals; Brain Mapping; Cerebral Cortex; Facial Expression; Humans; Motor Cortex; Neural Pathways; Neurosciences
PubMed: 15335441
DOI: 10.1097/01.nrl.0000138734.45742.8d