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NeuroImage Mar 2020The human brain coordinates a wide variety of motor activities. On a large scale, the cortical motor system is topographically organized such that neighboring body parts...
The human brain coordinates a wide variety of motor activities. On a large scale, the cortical motor system is topographically organized such that neighboring body parts are represented by neighboring brain areas. This homunculus-like somatotopic organization along the central sulcus has been observed using neuroimaging for large body parts such as the face, hands and feet. However, on a finer scale, invasive electrical stimulation studies show deviations from this somatotopic organization that suggest an organizing principle based on motor actions rather than body part moved. It has not been clear how the action-map organization principle of the motor cortex in the mesoscopic (sub-millimeter) regime integrates into a body map organization principle on a macroscopic scale (cm). Here we developed and applied advanced mesoscopic (sub-millimeter) fMRI and analysis methodology to non-invasively investigate the functional organization topography across columnar and laminar structures in humans. Compared to previous methods, in this study, we could capture locally specific blood volume changes across entire brain regions along the cortical curvature. We find that individual fingers have multiple mirrored representations in the primary motor cortex depending on the movements they are involved in. We find that individual digits have cortical representations up to 3 mm apart from each other arranged in a column-like fashion. These representations are differentially engaged depending on whether the digits' muscles are used for different motor actions such as flexion movements, like grasping a ball or retraction movements like releasing a ball. This research provides a starting point for non-invasive investigation of mesoscale topography across layers and columns of the human cortex and bridges the gap between invasive electrophysiological investigations and large coverage non-invasive neuroimaging.
Topics: Adult; Brain Mapping; Fingers; Humans; Magnetic Resonance Imaging; Motor Activity; Motor Cortex
PubMed: 31862526
DOI: 10.1016/j.neuroimage.2019.116463 -
Journal of Neurophysiology Sep 2000Using functional magnetic resonance imaging (fMRI), we measured regional blood flow to examine which motor areas of the human cerebral cortex are preferentially involved... (Clinical Trial)
Clinical Trial Comparative Study
Using functional magnetic resonance imaging (fMRI), we measured regional blood flow to examine which motor areas of the human cerebral cortex are preferentially involved in an auditory conditional motor behavior. As a conditional motor task, randomly selected 330 or 660 Hz tones were presented to the subjects every 1. 0 s. The low and high tones indicated that the subjects should initiate three successive opposition movements by tapping together the right thumb and index finger or the right thumb and little finger, respectively. As a control task, the same subjects were asked to alternate the two opposition movements, in response to randomly selected tones that were presented at the same frequencies. Between the two tasks, MRI images were also scanned in the resting state while the tones were presented in the same way. Comparing the images during each of the two tasks with images during the resting state, it was observed that several frontal motor areas, including the primary motor cortex, dorsal premotor cortex (PMd), supplementary motor area (SMA), and pre-SMA, were activated. However, preferential activation during the conditional motor task was observed only in the PMd and pre-SMA of the subjects' left (contralateral) frontal cortex. The PMd has been thought to play an important role in transforming conditional as well as spatial visual cues into corresponding motor responses, but our results suggest that the PMd along with the pre-SMA are the sites where more general and extensive sensorimotor integration takes place.
Topics: Acoustic Stimulation; Adult; Association Learning; Blood Flow Velocity; Brain Mapping; Cerebrovascular Circulation; Conditioning, Psychological; Cues; Female; Humans; Magnetic Resonance Imaging; Male; Motor Activity; Motor Cortex; Psychomotor Performance
PubMed: 10980036
DOI: 10.1152/jn.2000.84.3.1667 -
Acta Neurochirurgica Jul 2017Navigated transcranial magnetic stimulation (nTMS) is increasingly used for preoperative mapping of motor function, and clinical evidence for its benefit for brain tumor... (Review)
Review
INTRODUCTION
Navigated transcranial magnetic stimulation (nTMS) is increasingly used for preoperative mapping of motor function, and clinical evidence for its benefit for brain tumor patients is accumulating. In respect to language mapping with repetitive nTMS, literature reports have yielded variable results, and it is currently not routinely performed for presurgical language localization. The aim of this project is to define a common protocol for nTMS motor and language mapping to standardize its neurosurgical application and increase its clinical value.
METHODS
The nTMS workshop group, consisting of highly experienced nTMS users with experience of more than 1500 preoperative nTMS examinations, met in Helsinki in January 2016 for thorough discussions of current evidence and personal experiences with the goal to recommend a standardized protocol for neurosurgical applications.
RESULTS
nTMS motor mapping is a reliable and clinically validated tool to identify functional areas belonging to both normal and lesioned primary motor cortex. In contrast, this is less clear for language-eloquent cortical areas identified by nTMS. The user group agreed on a core protocol, which enables comparison of results between centers and has an excellent safety profile. Recommendations for nTMS motor and language mapping protocols and their optimal clinical integration are presented here.
CONCLUSION
At present, the expert panel recommends nTMS motor mapping in routine neurosurgical practice, as it has a sufficient level of evidence supporting its reliability. The panel recommends that nTMS language mapping be used in the framework of clinical studies to continue refinement of its protocol and increase reliability.
Topics: Brain Mapping; Humans; Language; Motor Cortex; Neuronavigation; Transcranial Magnetic Stimulation
PubMed: 28456870
DOI: 10.1007/s00701-017-3187-z -
Current Opinion in Neurobiology Dec 1996Humans and non-human primates have several motor areas. Exactly how many is a matter of current debate. A proper parcellation of motor areas must be based on correlated... (Review)
Review
Humans and non-human primates have several motor areas. Exactly how many is a matter of current debate. A proper parcellation of motor areas must be based on correlated structural and functional differences. Recent studies indicate that the primary motor cortex may be, in reality, two areas (4a and 4p). Similarly, there are undoubtedly two or more cingulate motor areas and perhaps two supplementary motor areas. The homologies between human and monkey brains are striking in some cases, making monkey models of human motor cortices attractive. The doctrine of a strict 'homuncular' somatotopical organization of motor areas will have to be abandoned. The engagement of motor areas in different types of voluntary seems merely a matter of degree of activation rather than exclusive specific contributions.
Topics: Animals; Haplorhini; Humans; Motor Cortex
PubMed: 9000024
DOI: 10.1016/s0959-4388(96)80027-4 -
Scientific Reports May 2018Human motor cortex can activate pelvic floor muscles (PFM), but the motor cortical representation of the PFM is not well characterized. PFM representation is thought to...
Human motor cortex can activate pelvic floor muscles (PFM), but the motor cortical representation of the PFM is not well characterized. PFM representation is thought to be focused in the supplementary motor area (SMA). Here we examine the degree to which PFM representation is distributed between SMA and the primary motor cortex (M1), and how this representation is utilized to activate the PFM in different coordination patterns. We show that two types of coordination patterns involving PFM can be voluntarily accessed: one activates PFM independently of synergists and a second activates PFM prior to and in proportion with synergists (in this study, the gluteus maximus muscle - GMM). Functional magnetic resonance imaging (fMRI) showed that both coordination patterns involve overlapping activation in SMA and M1, suggesting the presence of intermingled but independent neural populations that access the different patterns. Transcranial magnetic stimulation (TMS) confirmed SMA and M1 representation for the PFM. TMS also showed that, equally for SMA and M1, PFM can be activated during rest but GMM can only be activated after voluntary drive to GMM, suggesting that these populations are distinguished by activation threshold. We conclude that PFM representation is broadly distributed in SMA and M1 in humans.
Topics: Adult; Electromyography; Female; Healthy Volunteers; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Motor Cortex; Muscle Contraction; Pelvic Floor; Rest; Transcranial Magnetic Stimulation
PubMed: 29740105
DOI: 10.1038/s41598-018-25705-0 -
International Journal of Molecular... Aug 2020Rodent neocortical neurons undergo prominent postnatal development and maturation. The process is associated with structural and functional maturation of the axon...
Rodent neocortical neurons undergo prominent postnatal development and maturation. The process is associated with structural and functional maturation of the axon initial segment (AIS), the site of action potential initiation. In this regard, cell size and optimal AIS length are interconnected. In sensory cortices, developmental onset of sensory input and consequent changes in network activity cause phasic AIS plasticity that can also control functional output. In non-sensory cortices, network input driving phasic events should be less prominent. We, therefore, explored the relationship between postnatal functional maturation and AIS maturation in principal neurons of the primary motor cortex layer V (M1LV), a non-sensory area of the rat brain. We hypothesized that a rather continuous process of AIS maturation and elongation would reflect cell growth, accompanied by progressive refinement of functional output properties. We found that, in the first two postnatal weeks, cell growth prompted substantial decline of neuronal input resistance, such that older neurons needed larger input current to reach rheobase and fire action potentials. In the same period, we observed the most prominent AIS elongation and significant maturation of functional output properties. Alternating phases of AIS plasticity did not occur, and changes in functional output properties were largely justified by AIS elongation. From the third postnatal week up to five months of age, cell growth, AIS elongation, and functional output maturation were marginal. Thus, AIS maturation in M1LV is a continuous process that attunes the functional output of pyramidal neurons and associates with early postnatal development to counterbalance increasing electrical leakage due to cell growth.
Topics: Action Potentials; Age Factors; Animals; Axon Initial Segment; Cell Differentiation; Cells, Cultured; Growth; Models, Neurological; Motor Cortex; Motor Neurons; Neurogenesis; Neuronal Plasticity; Rats
PubMed: 32847128
DOI: 10.3390/ijms21176101 -
Biomedical Engineering Online Aug 2022Motor cortex stimulation applied as a clinical treatment for neuropathic disorders for decades. With stimulation electrodes placed directly on the cortical surface, this...
BACKGROUND
Motor cortex stimulation applied as a clinical treatment for neuropathic disorders for decades. With stimulation electrodes placed directly on the cortical surface, this neuromodulation method provides higher spatial resolution than other non-invasive therapies. Yet, the therapeutic effects reported were not in conformity with different syndromes. One of the main issues is that the stimulation parameters are always determined by clinical experience. The lack of understanding about how the stimulation current propagates in the cortex and various stimulation parameters and configurations obstruct the development of this method.
METHODS
In this study, we investigated the effect of different stimulation configurations on cortical responses to motor cortical stimulations using intrinsic optical imaging.
RESULTS
Our results showed that the cortical activation of electrical stimulation is not only related to the current density but also related to the propagation distance. Besides, stimulation configurations also affect the propagation of the stimulation current.
CONCLUSIONS
All these results provide preliminary experimental evidence for parameter and electrode configuration optimizations.
Topics: Electric Stimulation; Electrodes; Motor Cortex; Pilot Projects
PubMed: 36038875
DOI: 10.1186/s12938-022-01026-2 -
Cerebral Cortex (New York, N.Y. : 1991) 1996Our goal in this review is to provide an anatomical framework for the analysis of the motor functions of the medial wall of the hemisphere in humans and laboratory... (Review)
Review
Our goal in this review is to provide an anatomical framework for the analysis of the motor functions of the medial wall of the hemisphere in humans and laboratory primates. Converging evidence indicates that this region of the frontal lobe contains multiple areas involved in motor control. In the monkey, the medial wall contains four premotor areas that project directly to both the primary motor cortex and the spinal cord. These are the supplementary motor area (SMA) on the superior frontal gyrus and three motor areas buried within the cingulate sulcus. In addition, there is evidence that a fifth motor field, the pre-SMA, lies rostral to the SMA proper. Recent physiological observations provide evidence for functional differences among these motor fields. In the human, no consensus exists on the number of distinct motor fields on the medial wall. In this review, we summarize the results of positron emission tomography (PET) studies that examined functional activation on the medial wall of humans. Our analysis suggests that it is possible to identify at least four separate cortical areas on the medial wall. Each area appears to be relatively more involved in some aspects of motor behavior than others. These cortical areas in the human appear to be analogous to the pre-SMA, the SMA proper, and two of the cingulate motor areas of the monkey. We believe that these correspondences and the anatomical framework we describe will be important for unraveling the motor functions of the medial wall of the hemisphere.
Topics: Animals; Gyrus Cinguli; Haplorhini; Humans; Motor Cortex
PubMed: 8670662
DOI: 10.1093/cercor/6.3.342 -
Acta Physiologica Scandinavica Jun 1990In order to find out whether damage of the visual cortex (area 17) of the brain results in a functional reorganization of the motor cortex, experiments were carried out...
In order to find out whether damage of the visual cortex (area 17) of the brain results in a functional reorganization of the motor cortex, experiments were carried out with freely moving rabbits performing a food acquisition task in an experimental cage. Two rabbits served as controls, while in three rabbits the visual cortex was bilaterally damaged. Analysis of the activity of 575 neurons in the control and operated rabbits after the recovery of the original instrumental food acquisition behaviour revealed a marked difference in the behavioural specialization of the neurons in the motor cortex of two operated rabbits compared with the control animals. Although the same types of units as in the control rabbits could be found in the operated rabbits (M neurons activated in relation to body and limb movements, S neurons activated in relation to food seizure and L neurons activated in relation to learned food acquisition task), the number of S units was about half of that in the controls and the number of L units about double. The relative number of activations of the neurons in the operated rabbits was significantly less frequent during the food seizure and more frequent during the learned behaviour. This difference indicates a change in the pattern of behavioural specialization of the neurons in the motor cortex due to the damage of the visual cortex. In this reorganization, the motor cortex became more like (but not identical to) visual and limbic cortices that normally contain noticeably more L neurons than the motor cortex. The number of neurons activated in relation to the behaviour in the operated rabbits, as compared with the control animals, was smaller in the upper and larger in the lower layers of the motor cortex. This may indicate recruitment of new neurons from the lower cortical layers.
Topics: Animals; Behavior, Animal; Electrophysiology; Feeding Behavior; Female; Male; Motor Cortex; Neurons; Rabbits; Visual Cortex
PubMed: 2368623
DOI: 10.1111/j.1748-1716.1990.tb08936.x -
The Neuroscientist : a Review Journal... Jun 2004Recent studies on the functional organization and operational principles of motor cortical function, taken together, strongly support the notion that the motor cortex... (Review)
Review
Recent studies on the functional organization and operational principles of motor cortical function, taken together, strongly support the notion that the motor cortex controls the muscle activities subserving movements in an integrated manner. For example, during pointing the shoulder, elbow and wrist muscles appear to be controlled as a coupled functional system, rather than individually and separately. The pattern of intrinsic connections between motor cortical points is likely part of the explanation of this operational principle. So too is the manner in which muscles and muscle synergies are represented in the motor cortex. However, selection of movement-related muscle synergies is likely a dynamic process involving the functional linking of a variety of motor cortical points, rather than the selection of fixed patterns embedded in the motor cortical circuitry. One of the mechanisms that may be involved in the functional linking of motor cortical points is disinhibition. Thus, motor cortical points are recruited into action by selected excitation as well as by selected release from inhibition. The incoordination of limb movements in patients after a stroke may be understood, at least in part, as a disruption of the connections between motor cortical points and of the neural mechanisms involved in their functional linking.
Topics: Animals; Brain Mapping; Humans; Motor Cortex; Movement; Muscle, Skeletal; Neural Pathways
PubMed: 15155060
DOI: 10.1177/107385403262109