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Journal of the Neurological Sciences Jan 2001Most contemporary investigators who study the behavioral effects of lesions of the primate motor cortex evaluate their findings in comparison to those of other recent... (Review)
Review
Most contemporary investigators who study the behavioral effects of lesions of the primate motor cortex evaluate their findings in comparison to those of other recent investigators, but not in relation to the experimental neurologists who dominated this field around the mid-part of the 20th century. Utilizing selected recent reports, we demonstrate that these earlier papers, primarily those by D. Denny-Brown, provide valuable insights into the interpretation of some modern studies. Thus, we suggest that contemporary investigators of the primate motor cortex thoroughly review articles by the mid-20th century experimental neurologists. In addition, Denny-Brown and his contemporaries studied the effects of lesions in many other parts of the primate nervous system, and the associated reports are presumably also relevant to current investigations of these areas of the CNS.
Topics: Animals; History, 20th Century; Motor Cortex; Neurology; Primates
PubMed: 11137511
DOI: 10.1016/s0022-510x(00)00465-2 -
Journal of Neurophysiology Jun 2020Although motor cortex is integral in driving physical exertion, how its inherent properties influence decisions to exert is unknown. In this study, we examined how...
Although motor cortex is integral in driving physical exertion, how its inherent properties influence decisions to exert is unknown. In this study, we examined how anatomical properties of motor cortex are related to participants' subjective valuations of effort and their decisions to exert effort. We used computational modeling to characterize participants' subjective valuation of physical effort during an effort-based decision-making task in which they made choices about exerting different levels of hand-grip exertion. We also acquired structural MRI data from these participants and extracted anatomical measures of each individual's hand knob, the region of motor cortex recruited during hand-grip exertion. We found that individual participants' cortical thickness of hand knob was associated with their effort-based decisions regarding hand exertion. These data provide evidence that the anatomy of an individual's motor cortex is an important factor in decisions to engage in physical activity. How effortful a task feels is an integral aspect of human decision-making that influences choices to engage in physical activity. We show that properties of motor cortex (the brain region responsible for physical exertion) are related to assessments of effort and decisions to exert. These findings provide a link between the anatomical properties of motor cortex and the cognitive function of effort-based choice.
Topics: Adolescent; Adult; Decision Making; Female; Humans; Magnetic Resonance Imaging; Male; Motor Activity; Motor Cortex; Psychomotor Performance; Young Adult
PubMed: 32374197
DOI: 10.1152/jn.00118.2020 -
Neuroscience Jul 2018Recent studies have revealed that the ventral premotor cortex (PMv) of nonhuman primates plays a pivotal role in various behaviors that require the transformation of... (Review)
Review
Recent studies have revealed that the ventral premotor cortex (PMv) of nonhuman primates plays a pivotal role in various behaviors that require the transformation of sensory cues to appropriate actions. Examples include decision-making based on various sensory cues, preparation for upcoming motor behavior, adaptive sensorimotor transformation, and the generation of motor commands using rapid sensory feedback. Although the PMv has frequently been regarded as a single entity, it can be divided into at least five functionally distinct regions: F4, a dorsal convexity region immediately rostral to the primary motor cortex (M1); F5p, a cortical region immediately rostral to F4, lying within the arcuate sulcus; F5c, a ventral convexity region rostral to F4; and F5a, located in the caudal bank of the arcuate sulcus inferior limb lateral to F5p. Among these, F4 can be further divided into dorsal and ventral subregions (F4d and F4v), which are involved in forelimb and orofacial movements, respectively. F5p contains "mirror neurons" to understand others' actions based on visual and other types of information, and F4d and F5p work together as a functional complex involved in controlling forelimb and eye movements, most efficiently in the execution and completion of coordinated eye-hand movements for reaching and grasping under visual guidance. In contrast, F5c and F5a are hierarchically higher than the F4d, F5p, and F5v complexes, and play a role in decision-making based on various sensory discriminations. Hence, the PMv subregions form a hierarchically organized integral system from decision-making to eye-hand coordination under various behavioral circumstances.
Topics: Animals; Macaca; Motor Cortex
PubMed: 29715510
DOI: 10.1016/j.neuroscience.2018.04.033 -
Annual Review of Neuroscience 1985The concept of a separate premotor cortical field involved in the cerebral control of movement went out of favor among neurophysiologists during the quarter century from... (Review)
Review
The concept of a separate premotor cortical field involved in the cerebral control of movement went out of favor among neurophysiologists during the quarter century from 1952 to 1977, but recent studies have led to its rehabilitation. The premotor cortex appears to be one of at least three fields within the motor cortex, two others being the primary motor cortex and the supplementary motor cortex. Several proposals have been presented concerning the functional specializations of the premotor cortex. Although no specific hypotheses have very strong support at present, the best evidence favors a role for premotor cortex in the preparation for and the sensory guidance of movement.
Topics: Afferent Pathways; Animals; Efferent Pathways; Haplorhini; Humans; Motor Cortex; Movement; Psychomotor Performance; Terminology as Topic; Vasomotor System
PubMed: 3920943
DOI: 10.1146/annurev.ne.08.030185.000245 -
Advances in Neurology 1996
Review
Topics: Electric Stimulation; Humans; Motor Cortex; Tomography, Emission-Computed
PubMed: 8615207
DOI: No ID Found -
Neuron May 2020Voluntary movement initiation involves the modulations of large groups of neurons in the primary motor cortex (M1). Yet similar modulations occur during movement...
Voluntary movement initiation involves the modulations of large groups of neurons in the primary motor cortex (M1). Yet similar modulations occur during movement planning when no movement occurs. Here, we show that a sequential spatiotemporal pattern of excitability propagates across M1 prior to the movement initiation in one of two oppositely oriented directions along the rostro-caudal axis. Using spatiotemporal patterns of intracortical microstimulation, we find that reaction time increases significantly when stimulation is delivered against, but not with, the natural propagation direction. Functional connections among M1 units emerge at movement that are oriented along the same rostro-caudal axis but not during movement planning. Finally, we show that beta amplitude profiles can more accurately decode muscle activity when they conform to the natural propagating patterns. These findings provide the first causal evidence that large-scale, propagating patterns of cortical excitability are behaviorally relevant and may be a necessary component of movement initiation.
Topics: Animals; Beta Rhythm; Macaca mulatta; Male; Motor Cortex; Movement; Neurons; Reaction Time
PubMed: 32145183
DOI: 10.1016/j.neuron.2020.02.011 -
Scientific Reports Nov 2019Navigated transcranial magnetic stimulation (nTMS) over the supplementary motor area (SMA) may impact fine motor skills. This study evaluates different nTMS parameters...
Navigated transcranial magnetic stimulation (nTMS) over the supplementary motor area (SMA) may impact fine motor skills. This study evaluates different nTMS parameters in their capacity to affect fine motor performance on the way to develop an SMA mapping protocol. Twenty healthy volunteers performed a variety of fine motor tests during baseline and nTMS to the SMA using 5 Hz, 10 Hz, and theta-burst stimulation (TBS). Effects on performance were measured by test completion times (TCTs), standard deviation of inter-tap interval (SDIT), and visible coordination problems (VCPs). The predominant stimulation effect was slowing of TCTs, i.e. a slowdown of test performances during stimulation. Furthermore, participants exhibited VCPs like accidental use of contralateral limbs or inability to coordinate movements. More instances of significant differences between baseline and stimulation occurred during stimulation of the right hemisphere compared to left-hemispheric stimulation. In conclusion, nTMS to the SMA could enable new approaches in neuroscience and enable structured mapping approaches. Specifically, this study supports interhemispheric differences in motor control as right-hemispheric stimulation resulted in clearer impairments. The application of our nTMS-based setup to assess the function of the SMA should be applied in patients with changed anatomo-functional representations as the next step, e.g. among patients with eloquent brain tumors.
Topics: Adult; Brain Mapping; Female; Humans; Male; Motor Cortex; Motor Skills; Transcranial Magnetic Stimulation; Young Adult
PubMed: 31780823
DOI: 10.1038/s41598-019-54302-y -
Journal of Trace Elements in Medicine... Jan 2019Despite the vast distribution among tissues, the central nervous system (CNS) represents the main target of methylmercury (MeHg) toxicity. However, few studies have...
Despite the vast distribution among tissues, the central nervous system (CNS) represents the main target of methylmercury (MeHg) toxicity. However, few studies have evaluated the effects of MeHg exposure on the CNS at equivalent doses to human environmental exposure. In our study, we evaluated the motor cortex, an important area of motor control, in adult rats chronically exposed to MeHg in a concentration equivalent to those found in fish-eating populations exposed to mercury (Hg). The parameters evaluated were total Hg accumulation, oxidative stress, tissue damage, and behavioral assessment in functional actions that involved this cortical region. Our results show in exposed animals a significantly greater level of Hg in the motor cortex; increase of nitrite levels and lipid peroxidation, associated with decreased antioxidant capacity against peroxyl radicals; reduction of neuronal and astrocyte density; and poor coordination and motor learning impairment. Our data showed that chronic exposure at low doses to MeHg is capable of promoting damages to the motor cortex of adult animals, with changes in oxidative biochemistry misbalance, neurodegeneration, and motor function impairment.
Topics: Animals; Dose-Response Relationship, Drug; Male; Methylmercury Compounds; Motor Cortex; Motor Skills; Nerve Degeneration; Oxidative Stress; Rats; Rats, Wistar
PubMed: 30466930
DOI: 10.1016/j.jtemb.2018.09.004 -
Brain Research Dec 1990Intracortical microstimulation was used to define topographic sectors and the rostral border of primary motor cortex in adult macaques (Macaca mulatta). In the same...
Intracortical microstimulation was used to define topographic sectors and the rostral border of primary motor cortex in adult macaques (Macaca mulatta). In the same animals, injections of fluorescent tracers were made within defined regions of primary motor cortex. Retrogradely labeled neurons were topographically distributed in area 3a, with most neurons located in layer III, and fewer neurons situated in layers V and IV. These findings suggest that muscle afferent information, thought to be important in a closed-loop mode of function, may reach primary motor cortex directly from cortical area 3a.
Topics: Animals; Electric Stimulation; Fluorescent Dyes; Macaca mulatta; Motor Cortex; Neurons
PubMed: 2085789
DOI: 10.1016/0006-8993(90)90388-r -
Progress in Brain Research 2001
Review
Topics: Animals; Humans; Models, Neurological; Motor Cortex; Nerve Net; Neural Pathways; Neurons
PubMed: 11480279
DOI: 10.1016/s0079-6123(01)30017-1