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Cerebral Cortex (New York, N.Y. : 1991) Jun 2022Motor behavior results in complex exchanges of motor and sensory information across cortical regions. Therefore, fully understanding the cerebral cortex's role in motor...
Motor behavior results in complex exchanges of motor and sensory information across cortical regions. Therefore, fully understanding the cerebral cortex's role in motor behavior requires a mesoscopic-level description of the cortical regions engaged, their functional interactions, and how these functional interactions change with behavioral state. Mesoscopic Ca2+ imaging through transparent polymer skulls in mice reveals elevated activation of the dorsal cerebral cortex during locomotion. Using the correlations between the time series of Ca2+ fluorescence from 28 regions (nodes) obtained using spatial independent component analysis (sICA), we examined the changes in functional connectivity of the cortex from rest to locomotion with a goal of understanding the changes to the cortical functional state that facilitate locomotion. Both the transitions from rest to locomotion and from locomotion to rest show marked increases in correlation among most nodes. However, once a steady state of continued locomotion is reached, many nodes, including primary motor and somatosensory nodes, show decreases in correlations, while retrosplenial and the most anterior nodes of the secondary motor cortex show increases. These results highlight the changes in functional connectivity in the cerebral cortex, representing a series of changes in the cortical state from rest to locomotion and on return to rest.
Topics: Animals; Brain Mapping; Calcium; Diagnostic Imaging; Locomotion; Magnetic Resonance Imaging; Mice; Motor Cortex; Neural Pathways
PubMed: 34689209
DOI: 10.1093/cercor/bhab373 -
Brain Stimulation 2020Deep brain stimulation (DBS) is an effective treatment for movement disorders, yet its mechanisms of action remain unclear. One method used to study its circuit-wide...
BACKGROUND
Deep brain stimulation (DBS) is an effective treatment for movement disorders, yet its mechanisms of action remain unclear. One method used to study its circuit-wide neuromodulatory effects is functional magnetic resonance imaging (fMRI) which measures hemodynamics as a proxy of neural activity. To interpret functional imaging data, we must understand the relationship between neural and vascular responses, which has never been studied with the high frequencies used for DBS.
OBJECTIVE
To measure neurovascular coupling in the rat motor cortex during thalamic DBS.
METHOD
Simultaneous intrinsic optical imaging and extracellular electrophysiology was performed in the motor cortex of urethane-anesthetized rats during thalamic DBS at 7 different frequencies. We related Maximum Change in Reflectance (MCR) from the imaging data to Integrated Evoked Potential (IEP) and change in broadband power of multi-unit (MU) activity, computing Spearman's correlation to determine the strength of these relationships. To determine the source of these effects, we studied the contributions of antidromic versus orthodromic activation in motor cortex perfusion using synaptic blockers.
RESULTS
MCR, IEP and change in MU power increased linearly to 60 Hz and saturated at higher frequencies of stimulation. Blocking orthodromic transmission only reduced the DBS-induced change in optical signal by ∼25%, suggesting that activation of corticofugal fibers have a major contribution in thalamic-induced cortical activation.
CONCLUSION
DBS-evoked vascular response is related to both evoked field potentials as well as multi-unit activity.
Topics: Animals; Deep Brain Stimulation; Evoked Potentials; Magnetic Resonance Imaging; Male; Motor Cortex; Neurovascular Coupling; Rats; Rats, Sprague-Dawley; Thalamus
PubMed: 32289725
DOI: 10.1016/j.brs.2020.03.005 -
The European Journal of Neuroscience Apr 2020Exercise has been shown to counteract age-related volume decreases in the human brain, and in this imaging study, we ask whether the same holds true for the...
Exercise has been shown to counteract age-related volume decreases in the human brain, and in this imaging study, we ask whether the same holds true for the microstructure of the cortex. Healthy older adults (n = 47, 65-90 years old) either exercised three times a week on a stationary bike or maintained their usual physical routine over a 12-week period. Quantitative longitudinal relaxation rate (R ) magnetic resonance imaging (MRI) maps were made at baseline and after the 12-week intervention. R is commonly taken to reflect cortical myelin density. The change in R (ΔR ) was significantly increased in a region of interest (ROI) in the primary motor cortex containing motor outputs to the leg musculature in the exercise group relative to the control group (p = .04). The change in R in this ROI correlated with an increase in oxygen consumption at the first ventilatory threshold (VT1) (p = .04), a marker of improvement in submaximal aerobic performance. An exploratory analysis across the cortex suggested that the correlation was predominately confined to the leg representation in the motor cortex. This study suggests that microstructural declines in the cortex of older adults may be staved off by exercise.
Topics: Aged; Aged, 80 and over; Brain; Exercise; Humans; Magnetic Resonance Imaging; Motor Cortex; Myelin Sheath
PubMed: 31593327
DOI: 10.1111/ejn.14585 -
The Journal of Physiology Mar 2020Discrete and rhythmic dynamics are inherent components of (human) movements. We provide evidence that distinct human motor cortex circuits contribute to discrete and...
KEY POINTS
Discrete and rhythmic dynamics are inherent components of (human) movements. We provide evidence that distinct human motor cortex circuits contribute to discrete and rhythmic movements. Excitability of supragranular layer circuits of the human motor cortex was higher during discrete movements than during rhythmic movements. Conversely, more complex corticospinal circuits showed higher excitability during rhythmic movements than during discrete movements. No task-specific differences existed for corticospinal output neurons at infragranular layers. The excitability differences were found to be time(phase)-specific and could not be explained by the kinematic properties of the movements. The same task-specific differences were found between the last cycle of a rhythmic movement period and ongoing rhythmic movements.
ABSTRACT
Human actions entail discrete and rhythmic movements (DM and RM, respectively). Recent insights from human and animal studies indicate different neural control mechanisms for DM and RM, emphasizing the intrinsic nature of the task. However, how distinct human motor cortex circuits contribute to these movements remains largely unknown. In the present study, we tested distinct primary motor cortex and corticospinal circuits and proposed that they show differential excitability between DM and RM. Human subjects performed either 1) DM or 2) RM using their right wrist. We applied an advanced electrophysiological approach involving transcranial magnetic stimulation and peripheral nerve stimulation to test the excitability of the neural circuits. Probing was performed at different movement phases: movement initiation (MI, 20 ms after EMG onset) and movement execution (ME, 200 ms after EMG onset) of the wrist flexion. At MI, excitability at supragranular layers was significantly higher in DM than in RM. Conversely, excitability of more complex corticospinal circuits was significantly lower in DM than RM at ME. No task-specific differences were found for direct corticospinal output neurons at infragranular layers. The neural differences could not be explained by the kinematic properties of the movements and also existed between ongoing RM and the last cycle of RM. Our results therefore strengthen the hypothesis that different neural control mechanisms engage in DM and RM.
Topics: Electromyography; Humans; Motor Cortex; Movement; Transcranial Magnetic Stimulation; Wrist
PubMed: 32057108
DOI: 10.1113/JP278779 -
Scientific Reports Feb 2021Non-invasive brain stimulation techniques including repetitive transcranial magnetic stimulation (rTMS), continuous theta-burst stimulation (cTBS), paired associative...
Non-invasive brain stimulation techniques including repetitive transcranial magnetic stimulation (rTMS), continuous theta-burst stimulation (cTBS), paired associative stimulation (PAS), and transcranial direct current stimulation (tDCS) have been applied over the cerebellum to induce plasticity and gain insights into the interaction of the cerebellum with neo-cortical structures including the motor cortex. We compared the effects of 1 Hz rTMS, cTBS, PAS and tDCS given over the cerebellum on motor cortical excitability and interactions between the cerebellum and dorsal premotor cortex / primary motor cortex in two within subject designs in healthy controls. In experiment 1, rTMS, cTBS, PAS, and tDCS were applied over the cerebellum in 20 healthy subjects. In experiment 2, rTMS and PAS were compared to sham conditions in another group of 20 healthy subjects. In experiment 1, PAS reduced cortical excitability determined by motor evoked potentials (MEP) amplitudes, whereas rTMS increased motor thresholds and facilitated dorsal premotor-motor and cerebellum-motor cortex interactions. TDCS and cTBS had no significant effects. In experiment 2, MEP amplitudes increased after rTMS and motor thresholds following PAS. Analysis of all participants who received rTMS and PAS showed that MEP amplitudes were reduced after PAS and increased following rTMS. rTMS also caused facilitation of dorsal premotor-motor cortex and cerebellum-motor cortex interactions. In summary, cerebellar 1 Hz rTMS and PAS can effectively induce plasticity in cerebello-(premotor)-motor pathways provided larger samples are studied.
Topics: Adult; Cerebellum; Evoked Potentials, Motor; Female; Humans; Male; Motor Cortex; Neural Inhibition; Neural Pathways; Transcranial Direct Current Stimulation; Transcranial Magnetic Stimulation
PubMed: 33542291
DOI: 10.1038/s41598-021-82496-7 -
NeuroImage Oct 2018The relevance of human primary motor cortex (M1) for motor actions has long been established. However, it is still unknown how motor actions are represented, and whether...
The relevance of human primary motor cortex (M1) for motor actions has long been established. However, it is still unknown how motor actions are represented, and whether M1 contains an ordered somatotopy at the mesoscopic level. In the current study we show that a detailed within-limb somatotopy can be obtained in M1 during finger movements using Gaussian population Receptive Field (pRF) models. Similar organizations were also obtained for primary somatosensory cortex (S1), showing that individual finger representations are interconnected throughout sensorimotor cortex. The current study additionally estimates receptive field sizes of neuronal populations, showing differences between finger digit representations, between M1 and S1, and additionally between finger digit flexion and extension. Using the Gaussian pRF approach, the detailed somatotopic organization of M1 can be obtained including underlying characteristics, allowing for the in-depth investigation of cortical motor representation and sensorimotor integration.
Topics: Brain Mapping; Female; Fingers; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; Motor Cortex; Movement; Somatosensory Cortex; Young Adult
PubMed: 29940282
DOI: 10.1016/j.neuroimage.2018.06.062 -
NeuroImage Oct 2021Vocal flexibility is a hallmark of the human species, most particularly the capacity to speak and sing. This ability is supported in part by the evolution of a direct...
Vocal flexibility is a hallmark of the human species, most particularly the capacity to speak and sing. This ability is supported in part by the evolution of a direct neural pathway linking the motor cortex to the brainstem nucleus that controls the larynx the primary sound source for communication. Early brain imaging studies demonstrated that larynx motor cortex at the dorsal end of the orofacial division of motor cortex (dLMC) integrated laryngeal and respiratory control, thereby coordinating two major muscular systems that are necessary for vocalization. Neurosurgical studies have since demonstrated the existence of a second larynx motor area at the ventral extent of the orofacial motor division (vLMC) of motor cortex. The vLMC has been presumed to be less relevant to speech motor control, but its functional role remains unknown. We employed a novel ultra-high field (7T) magnetic resonance imaging paradigm that combined singing and whistling simple melodies to localise the larynx motor cortices and test their involvement in respiratory motor control. Surprisingly, whistling activated both 'larynx areas' more strongly than singing despite the reduced involvement of the larynx during whistling. We provide further evidence for the existence of two larynx motor areas in the human brain, and the first evidence that laryngeal-respiratory integration is a shared property of both larynx motor areas. We outline explicit predictions about the descending motor pathways that give these cortical areas access to both the laryngeal and respiratory systems and discuss the implications for the evolution of speech.
Topics: Adult; Female; Humans; Larynx; Least-Squares Analysis; Magnetic Resonance Imaging; Male; Motor Cortex; Neural Pathways; Respiration; Respiratory Mechanics; Rest; Singing; Speech; Young Adult
PubMed: 34216772
DOI: 10.1016/j.neuroimage.2021.118326 -
Ultrasonic thalamic stimulation modulates neural activity of thalamus and motor cortex in the mouse.Journal of Neural Engineering Dec 2021Previous studies have demonstrated that ultrasound thalamic stimulation (UTS) can treat disorders of consciousness. However, it is still unclear how UTS modulates neural...
Previous studies have demonstrated that ultrasound thalamic stimulation (UTS) can treat disorders of consciousness. However, it is still unclear how UTS modulates neural activity in the thalamus and cortex.In this study, we performed UTS in mice and recorded the neural activities including spike and local field potential (LFP) of the thalamus and motor cortex (M1). We analyzed the firing rate of spikes and the power spectrum of LFPs and evaluated the coupling relationship between LFPs from the thalamus and M1 with Granger causality.Our results clearly indicate that UTS can directly induce neural activity in the thalamus and indirectly induce neural activity in the M1. We also found that there is a strong connection relationship of neural activity between thalamus and M1 under UTS.These results demonstrate that UTS can modulate the neural activity of the thalamus and M1 in mice. It has the potential to provide guidance for the ultrasound treatment of thalamus-related diseases.
Topics: Animals; Consciousness; Mice; Motor Cortex; Thalamus; Ultrasonics
PubMed: 34875645
DOI: 10.1088/1741-2552/ac409f -
Arthritis Research & Therapy Jun 2015The aim of this study was to investigate possible differences in the organisation of the motor cortex in people with knee osteoarthritis (OA) and whether there is an... (Comparative Study)
Comparative Study
INTRODUCTION
The aim of this study was to investigate possible differences in the organisation of the motor cortex in people with knee osteoarthritis (OA) and whether there is an association between cortical organisation and accuracy of a motor task.
METHODS
fMRI data were collected while 11 participants with moderate/severe right knee OA (6 male, 69 ± 6 (mean ± SD) years) and seven asymptomatic controls (5 male, 64 ± 6 years) performed three visually guided, variable force, force matching motor tasks involving isolated isometric muscle contractions of: 1) quadriceps (knee), 2) tibialis anterior (ankle) and, 3) finger/thumb flexor (hand) muscles. fMRI data were used to map the loci of peak activation in the motor cortex during the three tasks and to assess whether there were differences in the organisation of the motor cortex between the groups for the three motor tasks. Root mean square of the difference between target and generated forces during muscle contraction quantified task accuracy.
RESULTS
A 4.1 mm anterior shift in the representation of the knee (p = 0.03) and swap of the relative position of the knee and ankle representations in the motor cortex (p = 0.003) were found in people with knee OA. Poorer performance of the knee task was associated with more anterior placement of motor cortex loci in people with (p = 0.05) and without (p = 0.02) knee OA.
CONCLUSIONS
Differences in the organisation of the motor cortex in knee OA was demonstrated in relation to performance of knee and ankle motor tasks and was related to quality of performance of the knee motor task. These results highlight the possible mechanistic link between cortical changes and modified motor behavior in people with knee OA.
Topics: Aged; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Motor Cortex; Osteoarthritis, Knee; Psychomotor Performance; Quadriceps Muscle
PubMed: 26080802
DOI: 10.1186/s13075-015-0676-4 -
Human Brain Mapping Jun 2019Sensorimotor control of neck muscles differs between individuals with and without pain. Differences in the primary motor cortex (M1) maps of these muscles may be...
Sensorimotor control of neck muscles differs between individuals with and without pain. Differences in the primary motor cortex (M1) maps of these muscles may be involved. This study compared M1 representations of deep (DNF) and superficial (SNF) neck flexor muscles between 10 individuals with neck pain (NP) and 10 painfree controls. M1 organisation was studied using transcranial magnetic stimulation (TMS) applied to a grid over the skull and surface electromyography of DNF (pharyngeal electrode) and SNF. Three-dimensional maps of M1 representation of each muscle were generated. Peaks in the SNF map that represented the sternocleidomastoid (SCM) and platysma muscles were identified. Unique centre of gravity (CoG)/map peaks were identified for the three muscles. In comparison to painfree controls, NP participants had more medial location of the CoG/peak of DNF, SCM, and platysma, greater mediolateral variation in DNF CoG (p = 0.02), fewer SNF and DNF map peaks (p = 0.01). These data show that neck flexor muscle M1 maps relate to trunk, neck, and face areas of the motor homunculus. Differences in M1 representation in NP have some similarities and some differences with observations for other musculoskeletal pain conditions. Despite the small sample size, our data did reveal differences and is comparable to other similar studies. The results of this study should be interpreted with consideration of methodological issues.
Topics: Adult; Electromyography; Female; Humans; Male; Motor Cortex; Neck Muscles; Neck Pain; Transcranial Magnetic Stimulation
PubMed: 30835902
DOI: 10.1002/hbm.24558