Non-primary Motor Areas Research Articles

Early cortico-muscular coherence and cortical network changes in Parkinson's patients treated with MRgFUS.

To investigate cortical network changes using Magnetoencephalography (MEG) signals in Parkinson's disease (PD) patients undergoing Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thalamotomy. We evaluated the MEG signals in 16 PD patients with drug-refractory tremor before and after 12-month from MRgFUS unilateral lesion of the ventralis intermediate nucleus (Vim) of the thalamus contralateral to the most affected body side. We recorded patients 24 h before (T0) and 24 h after MRgFUS (T1). We analyzed signal epochs recorded at rest and during the isometric extension of the hand contralateral to thalamotomy. We evaluated cortico-muscular coherence (CMC), the out-strength index from non-primary motor areas to the pre-central area and connectivity indexes, using generalized partial directed coherence. Statistical analysis was performed using RMANOVA and post hoct-tests. Most changes found at T1 compared to T0 occurred in the beta band and included: (1) a re-adjustment of CMC distribution; (2) a reduced out-strength from non-primary motor areas toward the precentral area; (3) strongly reduced clustering coefficient values. These differences mainly occurred during motor activation and with few statistically significant changes at rest. Correlation analysis showed significant relationships between changes of out-strength and clustering coefficient in non-primary motor areas and the changes in clinical scores. One day after MRgFUS thalamotomy, PD patients showed a topographically reordered CMC and decreased cortico-cortical flow, together with a reduced local connection between different nodes. These findings suggest that the reordered cortico-muscular and cortical-networks in the beta band may represent an early physiological readjustment related to MRgFUS Vim lesion.

Cortico-cortical connectivity changes during motor execution associated with sensory gating to frontal cortex: An rTMS study

As a change in the electroencephalogram (EEG) during motor tasks, the phenomenon in the sensorimotor area (SM1) is called event-related desynchronization (ERD). Motor commands are discharged from the primary motor area (M1) to the muscle through the corticospinal pathway and feedback to the primary somatosensory area (S1). This sensory input from the peripheral nerve stimulation to the central nervous system is attenuated during motor tasks by motor commands. This phenomenon is known as movement gating and is observed not only in S1, but also in non-primary motor areas. However, the brain circuits that trigger these motor-related changes and how the brain circuit modulates them as a controller remain unsolved. In this study, we evaluated the effects of spontaneous EEG changes and movement gating of somatosensory evoked potentials (SEPs) during motor execution by modulating cortical excitability with low-frequency repetitive transcranial magnetic stimulation (rTMS) over the PMc. Low frequency rTMS is known as an application where cortical excitability is suppressed after the stimulation. After rTMS, not only the previously known ERD, but also the newly gating of SEPs N30 and corticocortical spontaneous EEG changes were evaluated by Granger causality, which indicates that the time-varying causal relationship from the frontal to parietal area was significantly attenuated among eight healthy participants. These results suggest that spontaneous changes in EEG on SM1 and cortico-cortical connectivity during motor tasks are related to sensory feedback suppression of the frontal cortex.

NTMS mapping of non-primary motor areas in brain tumour patients and healthy volunteers.

Navigated transcranial magnetic stimulation (nTMS) has been increasingly used for presurgical cortical mapping of the primary motor cortex (M1) but remains controversial for the evaluation of non-primary motor areas (NPMA). This study investigates clinical and neurophysiological parameters in brain tumour patients and healthy volunteers to decide whether single-pulse biphasic nTMS allows to reliably elicite MEP outside from M1 or not. Twelve brain tumour patients and six healthy volunteers underwent M1 nTMS mapping. NPMA nTMS mapping followed using 120% and 150% M1 resting motor threshold (RMT) stimulation intensity. Spearman's correlation analysis tested the association of clinical and neurophysiological parameters between M1 and NPMA mapping. A total of 88.81% of nTMS stimulations in NPMA in patients/83.87% in healthy volunteers in patients/83.87% in healthy volunteers did not result in MEPs ≥ 50μV. Positive nTMS mapping in NPMA correlated with higher stimulation intensity and larger M1 areas in patients (120% M1 RMT SI p = 0.005/150% M1 RMT SI p = 0.198). Our findings indicate that in case of positive nTMS mapping in NPMA, MEPs originate mostly from M1. For future studies, MEP parameters and TMS coil rotation should be studied closely to assess the risk for postoperative motor deterioration.

A score to map the lateral nonprimary motor area: Multispectrum intrinsic brain activity versus cortical stimulation.

Multispectrum electrocorticographic components are critical for mapping the nonprimary motor area (NPMA). The objective of this study was to derive and validate a reliable scoring system for electrocorticography-based NPMA mapping (NPMA score) to replace electrical cortical stimulation (ECS) during brain surgery. We analyzed 14 consecutive epilepsy patients with subdural electrodes implanted in the frontal lobe at Kyoto University Hospital. The NPMA score was retrospectively derived from multivariate analysis in the derivation group (patients=7, electrodes=713, during 2010-2013) and validated in the validation group (patients=7, electrodes=772, during 2014-2017). We assessed the accuracy and reliability of the score relative to ECS in determining the NPMA and predicting postoperative functional outcomes. Multivariate analysis in the derivation group led to an 8-point score for predicting ECS-based NPMA (1 point for anatomical localization of the electrode and 1 or 2 points for movement-related electrocorticographic components regardless of somatotopy in very slow cortical potential shifts [<0.5Hz], 40-80-Hz band power increase, and 8-24-Hz band power decrease), which was validated in the validation group. The area under the receiver operating characteristic curve (AUC) was 0.89 in the derivation group. Good prediction (specificity = 94%, sensitivity = 100%) and discrimination (AUC=0.87) were reproduced in the validation group. Overall, higher NPMA scores identified 2 patients with postoperative deficits after frontal lobe resection. The NPMA score is reliable for NPMA mapping, potentially replacing ECS. It is a potential prognostic marker for postoperative functional deficits.

The Corticospinal Reserve Capacity: Reorganization of Motor Area and Excitability As a Novel Pathophysiological Concept in Cervical Myelopathy.

In degenerative cervical myelopathy (DCM), the dynamics of disease progression and the outcome after surgical decompression vary interindividually and do not necessarily correlate with radiological findings. To improve diagnostic power in DCM by better characterization of the underlying pathophysiology using navigated transcranial magnetic stimulation (nTMS). Eighteen patients with DCM due to cervical spinal canal stenosis were examined preoperatively with nTMS. On the basis of the initial Japanese Orthopedic Association (JOA) Score, 2 patient groups were established (JOA ≤12/>12). We determined the resting motor threshold, recruitment curve, cortical silent period, and motor area. Accordingly, 8 healthy subjects were examined. Although the resting motor threshold was comparable in both groups (P= .578), the corticospinal excitability estimated by the recruitment curve was reduced in patients (P= .022). In patients with only mild symptoms (JOA >12), a compensatory higher activation of non-primary motor areas was detected (P< .005). In contrast, patients with severe impairment (JOA ≤12) showed a higher cortical inhibition (P< .05) and reduced cortical motor area (P< .05) revealing a functional restriction on the cortical level. Based on these results, we propose a new concept for functional compensation for DCM on the cortical and spinal level, ie corticospinal reserve capacity. nTMS is a useful tool to noninvasively characterize the pattern of functional impairment and compensatory reorganization in patients suffering from DCM. The change in nTMS parameters might serve as a valuable prognostic factor in these patients in the future.

Ipsilateral corticotectal projections from the primary, premotor and supplementary motor cortical areas in adult macaque monkeys: a quantitative anterograde tracing study.

The corticotectal projection from cortical motor areas is one of several descending pathways involved in the indirect control of spinal motoneurons. In non-human primates, previous studies reported that cortical projections to the superior colliculus (SC) originated from the premotor cortex (PM) and the primary motor cortex, whereas no projection originated from the supplementary motor area (SMA). The aim of the present study was to investigate and compare the properties of corticotectal projections originating from these three cortical motor areas in intact adult macaques (n=9). The anterograde tracer biotinylated dextran amine was injected into one of these cortical areas in each animal. Individual axonal boutons, both en passant and terminaux, were charted and counted in the different layers of the ipsilateral SC. The data confirmed the presence of strong corticotectal projections from the PM. A new observation was that strong corticotectal projections were also found to originate from the SMA (its proper division). The corticotectal projection from the primary motor cortex was quantitatively less strong than that from either the premotor or SMAs. The corticotectal projection from each motor area was directed mainly to the deep layer of the SC, although its intermediate layer was also a consistent target of fairly dense terminations. The strong corticotectal projections from non-primary motor areas are in position to influence the preparation and planning of voluntary movements.

Alterations in Functional Cortical Hierarchy in Hemiparkinsonian Rats.

Parkinson's disease and experimentally induced hemiparkinsonism are characterized by increased beta synchronization between cortical and subcortical areas. This change in beta connectivity might reflect either a symmetric increase in interareal influences or asymmetric changes in directed influences among brain areas. We assessed patterns of functional and directed connectivity within and between striatum and six cortical sites in each hemisphere of the hemiparkinsonian rat model. LFPs were recorded in resting and walking states, before and after unilateral 6-hydroxydopamine lesion. The hemiparkinsonian state was characterized by increased oscillatory activity in the 20-40 Hz range in resting and walking states, and increased interhemispheric coupling (phase lag index) that was more widespread at rest than during walking. Spectral Granger-causality analysis revealed that the change in symmetric functional connectivity comprised profound reorganization of hierarchical organization and directed influence patterns. First, in the lesioned hemisphere, the more anterior, nonprimary motor areas located at the top of the cortical hierarchy (i.e., receiving many directed influences) tended to increase their directed influence onto the posterior primary motor and somatosensory areas. This enhanced influence of "higher" areas may be related to the loss of motor control due to the 6-OHDA lesion. Second, the drive from the nonlesioned toward the lesioned hemisphere (in particular to striatum) increased, most prominently during walking. The nature of these adaptations (disturbed signaling or compensation) is discussed. The present study demonstrates that hemiparkinsonism is associated with a profound reorganization of the hierarchical organization of directed influence patterns among brain areas, perhaps reflecting compensatory processes.SIGNIFICANCE STATEMENT Parkinson's disease classically first becomes manifest in one hemibody before affecting both sides, suggesting that degeneration is asymmetrical. Our results suggest that asymmetrical degeneration of the dopaminergic system induces an increased drive from the nonlesioned toward the lesioned hemisphere and a profound reorganization of functional cortical hierarchical organization, leading to a stronger directed influence of hierarchically higher placed cortical areas over primary motor and somatosensory cortices. These changes may represent a compensatory mechanism for loss of motor control as a consequence of dopamine depletion.

Corticobulbar projections from distinct motor cortical areas to the reticular formation in macaque monkeys.

Corticospinal and corticobulbar descending pathways act in parallel with brainstem systems, such as the reticulospinal tract, to ensure the control of voluntary movements via direct or indirect influences onto spinal motoneurons. The aim of this study was to investigate the corticobulbar projections from distinct motor cortical areas onto different nuclei of the reticular formation. Seven adult macaque monkeys were analysed for the location of corticobulbar axonal boutons, and one monkey for reticulospinal neurons' location. The anterograde tracer BDA was injected in the premotor cortex (PM), in the primary motor cortex (M1) or in the supplementary motor area (SMA), in 3, 3 and 1 monkeys respectively. BDA anterograde labelling of corticobulbar axons were analysed on brainstem histological sections and overlapped with adjacent Nissl-stained sections for cytoarchitecture. One adult monkey was analysed for retrograde CB tracer injected in C5-C8 hemispinal cord to visualise reticulospinal neurons. The corticobulbar axons formed bilateral terminal fields with boutons terminaux and en passant, which were quantified in various nuclei belonging to the Ponto-Medullary Reticular Formation (PMRF). The corticobulbar projections from both PM and SMA tended to end mainly ipsilaterally in PMRF, but contralaterally when originating from M1. Furthermore, the corticobulbar projection was less dense when originating from M1 than from non-primary motor areas (PM, SMA). The main nuclei of bouton terminals corresponded to the regions where reticulospinal neurons were located with CB retrograde tracing. In conclusion, the corticobulbar projection differs according to the motor cortical area of origin in density and laterality.

Increased Inhibition in Non-Primary Motor Areas of String-Instrument Players: A Preliminary Study with Paired-Pulse Transcranial Magnetic Stimulation.

Background: The muscle representations in non-primary motor area (NPMA) are located in the dorsal premotor area (PMd) and in the border region between the premotor area and the supplementary motor area (SMA).Objective: We characterized the plasticity of intracortical inhibitory and excitatory circuits in muscle representations in primary motor cortex (M1) and in NPMA related to acquired fine motor skills. We compared local cortical inhibition and facilitation balance in M1 and in NPMA between control subjects (n = 6) and right-handed string-instrument players (n = 5).Methods: Navigated transcranial magnetic stimulation (TMS) was used to compare motor thresholds (MTs), motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in non-dominant hand muscle representations in M1 and NPMA.Results: String-instrument players showed reduced SICI in M1 in the actively used left hand abductor digiti minimi (ADM) muscle representation at 3 ms inter-stimulus interval (ISI) with a conditioning stimulus (CS) intensity of 80% of MT and increased SICI in NPMA in ADM representation at 2 ms ISI and CS intensity of 50% of MT in comparison with controls. No differences between string-instrument players and controls were found for the SICI in the left hand opponens pollicis (OP) muscle representation, which is a muscle not intensively trained in string-instrument players.Conclusions: These preliminary results indicate that the stronger inhibition in motor representations outside M1 in string-instrument players may be crucial when accurate movements of single muscles must be performed. In contrast, weaker inhibition in M1 in string-instrument players may benefit the performance of fast finger movements.

Neuromuscular Plasticity: Disentangling Stable and Variable Motor Maps in the Human Sensorimotor Cortex.

Motor maps acquired with transcranial magnetic stimulation (TMS) are evolving as a biomarker for monitoring disease progression or the effects of therapeutic interventions. High test-retest reliability of this technique for long observation periods is therefore required to differentiate daily or weekly fluctuations from stable plastic reorganization of corticospinal connectivity. In this study, a novel projection, interpolation, and coregistration technique, which considers the individual gyral anatomy, was applied in healthy subjects for biweekly acquired TMS motor maps over a period of twelve weeks. The intraclass correlation coefficient revealed long-term reliability of motor maps with relevant interhemispheric differences. The sensorimotor cortex and nonprimary motor areas of the dominant hemisphere showed more extended and more stable corticospinal connectivity. Long-term correlations of the MEP amplitudes at each stimulation site revealed mosaic-like clusters of consistent corticospinal excitability. The resting motor threshold, centre of gravity, and mean MEPs across all TMS sites, as highly reliable cortical map parameters, could be disentangled from more variable parameters such as MEP area and volume. Cortical TMS motor maps provide high test-retest reliability for long-term monitoring when analyzed with refined techniques. They may guide restorative interventions which target dormant corticospinal connectivity for neurorehabilitation.

Differential effects of continuous theta burst stimulation over left premotor cortex and right prefrontal cortex on modulating upper limb somatosensory input

Somatosensory evoked potentials (SEPs) represent somatosensory processing in non-primary motor areas (i.e. frontal N30 and N60) and somatosensory cortices (i.e. parietal P50). It is well-known that the premotor cortex (PMC) and prefrontal cortex (PFC) are involved in the preparation and planning of upper limb movements but it is currently unclear how they modulate somatosensory processing for upper limb motor control. In the current study, two experiments examined SEP modulations after continuous theta burst stimulation (cTBS) was used to transiently disrupt the left PMC (Experiment 1) and right PFC (Experiment 2). Both Experiment 1 (n=15) and Experiment 2 (n=16) used pre-post experimental designs. In both experiments participants performed a task requiring detection of varying amplitudes of attended vibrotactile (VibT) stimuli to the left index finger (D2) and execution of a pre-matched finger sequence with the right (contralateral) hand to specific VibT targets. During the task, SEPs were measured to median nerve (MN) stimulations time-locked during pre-stimulus (250ms before VibT), early response selection (250ms after VibT), late preparatory (750ms after VibT) and execution (1250ms VibT) phases. The key findings of Experiment 1 revealed significant decreases in N30 and N60 peak amplitudes after cTBS to PMC. In contrast, the results of Experiment 2, also found significant decreased N60 peak amplitudes as well as trends for increased N30 and P50 peak amplitudes. A direct comparison of Experiment 1 and Experiment 2 confirmed differential modulation of N30 peak amplitudes after PMC (gated) compared to PFC (enhanced) cTBS. Collectively, these results support that both the left PMC and right PFC have modulatory roles on early somatosensory input into non-primary motor areas, such as PMC and supplementary motor area (SMA), represented by frontal N30 and N60 SEPs. These results confirm that PMC and PFC are both part of a network that regulates somatosensory input for upper limb motor control.

P101. Impact of aging on motor control networks underlying movement selection and initiation

Introduction Healthy elderly adults typically show greater regional activity in frontoparietal brain regions relative to young adults when performing motor control tasks ( Ward and Frackowiak, 2003 , Vallesi et al., 2011 ). However, the functional role of enhanced activity within the motor network is still a matter of debate. One hypothesis is that higher levels of neural activity reflect a compensatory mechanism to account for age-related decline in neural networks. We, therefore, used a systems-level approach to investigate networks dynamics underlying motor control in young and elderly subjects. We hypothesized that advanced aging is associated with reduced connectivity in the basic motor network, which is compensated by stronger influence of non-primary motor areas like prefrontal cortex. Methods We scanned 12 young (age 22–33) and 12 elderly subjects (age 52–74) employing a computerized task involving both basic (finger tapping) and higher motor control processing (internally and externally cued movement selection and initiation). Dynamic Causal Modelling (DCM) for fMRI was used to assess effective connectivity in a bilateral frontoparietal network comprising dorsolateral prefrontal cortex, dorsal premotor cortex, intraparietal cortex and primary motor cortex. Results Elderly subjects showed a significant slowing in movement selection and initiation. This slowing was accompanied by increases in both regional brain activity and effective connectivity between frontoparietal brain regions in elderly compared to young subjects. However, within the group of elderly subjects, coupling strengths of premotor cortex with primary motor cortex and intraparietal cortex decreased with advancing age, whereas connectivity between prefrontal and premotor cortex increased as a function of age. Discussion Network interactions underlying visuomotor transformation (parietal-premotor) and motor execution (premotor-primary motor cortex) follow an U-curve relationship: Connectivity is generally elevated in old relative to young subjects, yet decreases with advanced aging. In contrast, prefrontal influences on premotor cortex increase with advanced aging. These findings are in line with the ”posterior to anterior shift theory” described for regional brain activity, thereby extending it to network interactions related to higher motor control ( Davis et al., 2008 ).

Somatosensory input to non-primary motor areas is enhanced during preparation of cued contraterlateral finger sequence movements

Frontal N30 somatosensory evoked potentials (SEPs) represent early somatosensory input into non-primary motor areas. Importantly, modulations of frontal N30 SEPs can provide insight into the mechanisms involved in sensory processing for movement control. Enhancements of frontal N30 SEPs have been revealed during repetitive but not during the preparation of movements that are contralateral to median nerve (MN) stimulation (i.e. contralateral movements). Importantly, these enhancements during contralateral movements may be dependent on increased activity in several neural areas such as the primary motor cortex (M1), supplementary motor area (SMA) and basal ganglia (BG). Furthermore, research has also shown that patients with prefrontal lesions have enhanced early frontal SEPs (i.e. N28) at rest supporting a role of the prefrontal cortex in inhibitory modulation of early somatosensory input. The current study evaluated whether differential modulations of frontal N30 SEPs occurred during different time periods when individuals prepared and executed contralateral (right) finger sequences to attended vibrotactile (VibT) stimuli at the left index finger. SEPs were measured to median nerve (MN) stimuli elicited at the left wrist and MN stimuli were time-locked in four different periods relative to VibT onset (during pre-stimulus, early response preparation, late movement preparation and movement execution). Results revealed that frontal N30 SEPs were significantly enhanced when MN stimulation occurred in the late preparatory and/or early movement execution period (∼750ms) after the attended VibT stimuli. This result supports that increases in frontal N30 amplitudes during contralateral movements are dependent on the complexity of preparing and executing finger sequences, which is associated with increased activity in several neural areas such as the non-primary motor areas, prefrontal cortex and BG. Furthermore, enhanced N30 SEPs during contralateral movement preparation and execution may be a necessary mechanism to decrease sensory gating to facilitate somatosensory processing in non-primary motor areas when there is a ‘noisy’ environment.

Neuroanatomical correlates of brain–computer interface performance

Brain–computer interfaces (BCIs) offer a potential means to replace or restore lost motor function. However, BCI performance varies considerably between users, the reasons for which are poorly understood. Here we investigated the relationship between sensorimotor rhythm (SMR)-based BCI performance and brain structure. Participants were instructed to control a computer cursor using right- and left-hand motor imagery, which primarily modulated their left- and right-hemispheric SMR powers, respectively. Although most participants were able to control the BCI with success rates significantly above chance level even at the first encounter, they also showed substantial inter-individual variability in BCI success rate. Participants also underwent T1-weighted three-dimensional structural magnetic resonance imaging (MRI). The MRI data were subjected to voxel-based morphometry using BCI success rate as an independent variable. We found that BCI performance correlated with gray matter volume of the supplementary motor area, supplementary somatosensory area, and dorsal premotor cortex. We suggest that SMR-based BCI performance is associated with development of non-primary somatosensory and motor areas. Advancing our understanding of BCI performance in relation to its neuroanatomical correlates may lead to better customization of BCIs based on individual brain structure.

Modulatory effects of movement sequence preparation and covert spatial attention on early somatosensory input to non-primary motor areas.

Early frontal somatosensory evoked potentials (SEPs) (i.e., N30) are known to be modulated by movement. Furthermore, individuals with prefrontal lesions have enhanced early frontal SEPs. However, it is currently unclear through what mechanism the prefrontal cortex may modulate early frontal SEPs. The current study investigated whether prefrontal modulatory effects on frontal SEPs may depend on the relevancy of somatosensory input for movement (i.e., interaction with motor areas). Two experiments were conducted to determine whether selective spatial attention alone (Experiment 1-Attend and Mentally Count) or when using attended somatosensory input in the preparation of finger sequences with the limb contralateral to somatosensory stimulation (Experiment 2-Attend for Movement Preparation) could modulate SEPs. In Experiment 1, SEPs elicited by median nerve (MN) stimulation at both wrists were measured in trials when individuals attended and mentally counted vibrotactile (VibT) input at either index finger. In Experiment 2, SEPs elicited by MN stimulation at the left wrist were measured in trials when individuals used attended VibT input at the left index finger to prepare finger sequences that were contralateral to MN stimulation. In both experiments, control conditions were performed where participants received passive VibT and MN stimulation. Results from Experiment 1 confirmed that selective spatial attention alone does not modulate frontal N30 peak amplitudes. However, Experiment 2 revealed that frontal N30 peak amplitudes were decreased (i.e., gated) when individuals used attended VibT input at the left index finger to prepare contralateral finger sequences. These results support a role of sensory gating of early frontal SEPs during finger sequence preparation of the limb contralateral to MN stimulation that may result from increased activity in prefrontal, motor preparatory areas, and basal ganglia.

A Longitudinal Study of Hand Motor Recovery after Sub-Acute Stroke: A Study Combined fMRI with Diffusion Tensor Imaging

Previous studies have shown that motor recovery of stroke can be assessed by the cortical activity and the structural integrity of the corticospinal tract (CST), but little is known about the relation between the cortical activity and the structural integrity during motor recovery. In the present study, we investigated the changes in brain activities evoked by twenty days’ functional electrical stimulation (FES) training in twelve sub-acute stroke patients with unilateral upper-limb disability. We compared cortex activity evoked by wrist movement of eleven stroke patients to that of eleven age-matched healthy subjects to figure out how cortex activity changed after stroke. We also measured the structural integrity represented by the fractional anisotropy (FA) asymmetry of the posterior limb of the internal capsule (PLIC) to find the relationship between the brain activity and the structure integrity. In our study, we found that patients with sub-acute stroke have shown greater activity in the contralesional primary motor cortex (M1) during the affected hand’s movement compared with healthy group, while the activity in ipsilesional M1 was decreased after the therapy compared to that before therapy, and the contralesional non-primary motor cortex showed greater activity after therapy. At the baseline we found that the positive correlation between the FA asymmetry of PLIC and the contralesional non-primary motor cortex activity showed that the greater damaged CST, the greater contralesional non-primary motor cortex recruited. While the negative correlation between them after the FES training indicates that after recovery the non-primary motor cortex plays different role in different stroke phases. Our study demonstrates that functional organization of a residual distributed motor system is related to the degree of disruption to the CST, and the non-primary motor areas plays an important role in motor recovery.

How does a surgeon’s brain buzz? An EEG coherence study on the interaction between humans and robot

IntroductionIn humans, both primary and non-primary motor areas are involved in the control of voluntary movements. However, the dynamics of functional coupling among different motor areas have not been fully clarified yet. There is to date no research looking to the functional dynamics in the brain of surgeons working in laparoscopy compared with those trained and working in robotic surgery.Experimental proceduresWe enrolled 16 right-handed trained surgeons and assessed changes in intra- and inter-hemispheric EEG coherence with a 32-channels device during the same motor task with either a robotic or a laparoscopic approach. Estimates of auto and coherence spectra were calculated by a fast Fourier transform algorithm implemented on Matlab 5.3.ResultsWe found increase of coherence in surgeons performing laparoscopy, especially in theta and lower alpha activity, in all experimental conditions (M1 vs. SMA, S1 vs. SMA, S1 vs. pre-SMA and M1 vs. S1; p < 0.001). Conversely, an increase in inter-hemispheric coherence in upper alpha and beta band was found in surgeons using the robotic procedure (right vs. left M1, right vs. left S1, right pre-SMA vs. left M1, left pre-SMA vs. right M1; p < 0.001).DiscussionOur data provide a semi-quantitative evaluation of dynamics in functional coupling among different cortical areas in skilled surgeons performing laparoscopy or robotic surgery. These results suggest that motor and non-motor areas are differently activated and coordinated in surgeons performing the same task with different approaches. To the best of our knowledge, this is the first study that tried to assess semi-quantitative differences during the interaction between normal human brain and robotic devices.

Neural correlates of motor impairment during motor imagery and motor execution in sub-cortical stroke

Objective: This study aims at identifying the neural substrates for motor execution (ME) and motor imagery (MI) in patients after stroke and their correlations with functional outcomes.Methods: 10 chronic stroke patients with left sub-cortical lesions and 10 unimpaired subjects were recruited. Their cortical processes were studied when they were asked to perform ME and MI unimanually using their unaffected and affected wrists during fMRI.Results: From correlation results, the supplementary motor area (SMA), its activation volume and congruence in functional neuroanatomy associated with ME and MI using affected wrist positively correlated with motor performance. During ME of the affected wrist, the precuneus, its activation volume and congruence in functional neuroanatomy between patient and unimpaired groups showed a negative correlation, while, in non-primary motor areas, the hemispheric balance of premotor cortex and the congruence in functional neuroanatomy of contralesional inferior parietal lobule between patient and unimpaired groups showed a positive correlation with motor performance.Conclusions: The non-primary motor-related areas were revealed to play a critical role in determining motor outcomes after left sub-cortical stroke, which was demonstrated in the stroke patients. In particular, SMA might be the key neural substrate associated with motor recovery.

Promoting endogenous associative plasticity in human primary motor cortex

Promoting endogenous associative plasticity in human primary motor cortex

Neuronal–glial alterations in non-primary motor areas in chronic subcortical stroke

Whether functional changes of the non-primary motor areas, e.g., dorsal premotor (PMd) and supplementary motor (SMA) areas, after stroke, reflect reorganization phenomena or recruitment of a pre-existing motor network remains to be clarified. We hypothesized that cellular changes in these areas would be consistent with their involvement in post-stroke reorganization. Specifically, we expected that neuronal and glial compartments would be altered in radiologically normal-appearing, i.e., spared, PMd and SMA in patients with arm paresis. Twenty survivors of a single ischemic subcortical stroke and 16 age-matched healthy controls were included. At more than six months after stroke, metabolites related to neuronal and glial compartments: N-acetylaspartate, myo-inositol, and glutamate/glutamine, were quantified by proton magnetic resonance spectroscopy in PMd and SMA in both injured (ipsilesional) and un-injured (contralesional) hemispheres. Correlations between metabolites were also calculated. Finally, relationships between metabolite concentrations and arm motor impairment (total and proximal Fugl-Meyer Upper Extremity, FMUE, scores) were analyzed. Compared to controls, stroke survivors showed significantly higher ipsilesional PMd myo-inositol and lower SMA N-acetylaspartate. Significantly lower metabolite correlations were found between ipsilesional and contralesional SMA. Ipsilesional N-acetylaspartate was significantly related to proximal FMUE scores. This study provides evidence of abnormalities in metabolites, specific to neuronal and glial compartments, across spared non-primary motor areas. Ipsilesional alterations were related to proximal arm motor impairment. Our results suggest the involvement of these areas in post-stroke reorganization.