Ipsilateral Sensorimotor Cortex Research Articles

Neural Correlates of Motor/Tactile Imagery and Tactile Sensation in a BCI paradigm: A High-Density EEG Source Imaging Study.

Complementary to brain-computer interface (BCI) based on motor imagery (MI) task, sensory imagery (SI) task provides a way for BCI construction using brain activity from somatosensory cortex. The underlying neurophysiological correlation between SI and MI was unclear and difficult to measure through behavior recording. In this study, we investigated the underlying neurodynamic of motor/tactile imagery and tactile sensation tasks through a high-density electroencephalogram (EEG) recording, and EEG source imaging was used to systematically explore the cortical activation differences and correlations between the tasks. In the experiment, participants were instructed to perform the left and right hand tasks in MI paradigm, sensory stimulation (SS) paradigm and SI paradigm. The statistical results demonstrated that the imagined MI and SI tasks differed from each other within ipsilateral sensorimotor scouts, frontal and right temporal areas in α bands, whereas real SS and imagined SI showed a similar activation pattern. The similarity between SS and SI may provide a way to train the BCI system, while the difference between MI and SI may provide a way to integrate the discriminative information between them to enhance BCI performance. The combination of the tasks and its underlying neurodynamic would provide a new approach for BCI designation for a wider application. BCI studies concentrate on the hybrid decoding method combining MI or SI with SS, but the underlining neurophysiological correlates between them were unclear. MI and SI differed from each other within the ipsilateral sensorimotor cortex in alpha bands. This is a first study to investigate the neurophysiological relationship between MI and SI through an EEG source imaging approach from high-density EEG recording.

Mapping Subcortico-Cortical Coupling-A Comparison of Thalamic and Subthalamic Oscillations.

The ventral intermediate nucleus of the thalamus (VIM) is an effective target for deep brain stimulation in tremor patients. Despite its therapeutic importance, its oscillatory coupling to cortical areas has rarely been investigated in humans. The objective of this study was to identify the cortical areas coupled to the VIM in patients with essential tremor. We combined resting-state magnetoencephalography with local field potential recordings from the VIM of 19 essential tremor patients. Whole-brain maps of VIM-cortex coherence in several frequency bands were constructed using beamforming and compared with corresponding maps of subthalamic nucleus (STN) coherence based on data from 19 patients with Parkinson's disease. In addition, we computed spectral Granger causality. The topographies of VIM-cortex and STN-cortex coherence were very similar overall but differed quantitatively. Both nuclei were coupled to the ipsilateral sensorimotor cortex in the high-beta band; to the sensorimotor cortex, brainstem, and cerebellum in the low-beta band; and to the temporal cortex, brainstem, and cerebellum in the alpha band. High-beta coherence to sensorimotor cortex was stronger for the STN (P = 0.014), whereas low-beta coherence to the brainstem was stronger for the VIM (P = 0.017). Although the STN was driven by cortical activity in the high-beta band, the VIM led thesensorimotor cortex in the alpha band. Thalamo-cortical coupling is spatially and spectrally organized. The overall similar topographies of VIM-cortex and STN-cortex coherence suggest that functional connections are not necessarily unique to one subcortical structure but might reflect larger frequency-specific networks involving VIM and STN to a different degree. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

DBS-evoked cortical responses index optimal contact orientations and motor outcomes in Parkinson’s disease

Although subthalamic deep brain stimulation (DBS) is a highly-effective treatment for alleviating motor dysfunction in patients with Parkinson’s disease (PD), clinicians currently lack reliable neurophysiological correlates of clinical outcomes for optimizing DBS parameter settings, which may contribute to treatment inefficacies. One parameter that could aid DBS efficacy is the orientation of current administered, albeit the precise mechanisms underlying optimal contact orientations and associated clinical benefits are not well understood. Herein, 24 PD patients received monopolar stimulation of the left STN during magnetoencephalography and standardized movement protocols to interrogate the directional specificity of STN-DBS current administration on accelerometer metrics of fine hand movements. Our findings demonstrate that optimal contact orientations elicit larger DBS-evoked cortical responses in the ipsilateral sensorimotor cortex, and importantly, are differentially predictive of smoother movement profiles in a contact-dependent manner. Moreover, we summarize traditional evaluations of clinical efficacy (e.g., therapeutic windows, side effects) for a comprehensive review of optimal/non-optimal STN-DBS contact settings. Together, these data suggest that DBS-evoked cortical responses and quantitative movement outcomes may provide clinical insight for characterizing the optimal DBS parameters necessary for alleviating motor symptoms in patients with PD in the future.

Effects of auditory feedback on fine motor output and corticomuscular coherence during a unilateral finger pinch task.

Auditory feedback is important to reduce movement error and improve motor performance during a precise motor task. Accurate motion guided by auditory feedback may rely on the neural muscle transmission pathway between the sensorimotor area and the effective muscle. However, it remains unclear how neural activities and sensorimotor loops play a role in enhancing performance. The present study uses an auditory feedback system by simultaneously recording electroencephalogram (EEG), electromyography (EMG), and exert force information to measure corticomuscular coherence (CMC), neural activity, and motor performance during precise unilateral right-hand pinch by using the thumb and the index finger with and without auditory feedback. This study confirms three results. First, compared with no auditory feedback, auditory feedback decreases movement errors. Second, compared with no auditory feedback, auditory feedback decreased the power spectrum in the beta band in the bimanual sensorimotor cortex and the alpha band in the ipsilateral sensorimotor cortex. Finally, CMC was computed between effector muscle of right hand and contralateral sensorimotor cortex. Analyses reveals that the CMC of beta band significantly decreases in auditory feedback condition compared with no auditory feedback condition. The results indicate that auditory feedback decreases the power spectral in the alpha and beta bands and decreases corticospinal connection in the beta band during precise hand control. This study provides a new perspective on the effect of auditory feedback on behavior and brain activity and offers a new idea for designing more suitable and effective rehabilitation and training strategies to improve fine motor performance.

Pretherapeutic functional connectivity of tractography-based targeting of the ventral intermediate nucleus for predicting tremor response in patients with Parkinson's disease after thalamotomy with MRI-guided focused ultrasound.

Tractography-based direct targeting of the ventral intermediate nucleus (T-VIM) is a novel method that provides patient-specific VIM coordinates. This study aimed to explore the accuracy and predictive value of using T-VIM in combination with tractography and resting-state functional connectivity techniques to perform magnetic resonance imaging-guided focused ultrasound (MRgFUS) thalamotomy as a treatment of Parkinson's disease (PD). PD patients underwent MRgFUS thalamotomy and were recruited for functional MRI scanning. A subscore of the Clinical Rating Scale for Tremor was used to evaluate tremor improvement. T-VIM and surgical VIM (S-VIM) were defined on preoperative diffusion tensor MRI and 24-hour postoperative T1-weighted imaging, respectively. The overlapping volume and center distance between S-VIM and T-VIM were measured to determine their correlations with 12-month postoperative tremor improvement. Moreover, pretherapeutic functional connectivity of T-VIM or S-VIM, based on region-of-interest connectivity and whole-brain seed-to-voxel connectivity, was measured with the resting-state functional connectivity technique to investigate their correlations with tremor improvement. All patients had excellent tremor improvement (mean [range] tremor improvement 74.82% [50.00%-94.44%]). The authors found that both overlapping volume and center distance between T-VIM and S-VIM were significantly correlated with tremor improvement (r = 0.788 and p = 0.012 for overlapping volume; r = -0.696 and p = 0.037 for center distance). Pretherapeutic functional connectivity of T-VIM with the ipsilateral sensorimotor cortex (r = 0.876 and p = 0.002), subthalamic nucleus (r = 0.700 and p = 0.036), and visual area (r = 0.911 and p = 0.001) was significantly and positively correlated with tremor improvement. T-VIM may improve the clinical application of MRgFUS thalamotomy as a treatment of PD. Pretherapeutic functional connectivity of T-VIM with the ipsilateral sensorimotor cortex, subthalamic nucleus, and visual area may predict PD tremor responses after MRgFUS thalamotomy.

Coherent Structural and Functional Network Changes after Thalamic Lesions in Essential Tremor.

Magnetic resonance-guided focused ultrasound of the ventral intermediate nucleus is a novel incisionless ablative treatment for essential tremor (ET). The aim was to study the structural and functional network changes induced by unilateral sonication of the ventral intermediate nucleus in ET. Fifteen essential tremor patients (66.2 ± 15.4 years) underwent probabilistic tractography and functional magnetic resonance imaging (MRI) during unilateral postural tremor-eliciting tasks using 3-T MRI before, 1 month (N=15), and 6 months (N=10) post unilateral sonication. Tractography identified tract-specific alterations within the dentato-thalamo-cortical tract (DTCT) affected by the unilateral lesion after sonication. Relative to the treated hand, task-evoked activation was significantly reduced in contralateral primary sensorimotor cortex and ipsilateral cerebellar lobules IV/V and VI, and vermis. Dynamic causal modeling revealed a significant decrease in excitatory drive from the cerebellum to the contralateral sensorimotor cortex. Thalamic lesions induced by sonication induce specific functional network changes within the DTCT, notably reducing excitatory input to ipsilateral sensorimotor cortex in ET. ©[2022] International Parkinson and Movement Disorder Society. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Harnessing cortical plasticity via gabapentinoid administration promotes recovery after stroke.

Stroke causes devastating sensory-motor deficits and long-term disability due to disruption of descending motor pathways. Restoration of these functions enables independent living and therefore represents a high priority for those afflicted by stroke. Here, we report that daily administration of gabapentin, a clinically approved drug already used to treat various neurological disorders, promotes structural and functional plasticity of the corticospinal pathway after photothrombotic cortical stroke in adult mice. We found that gabapentin administration had no effects on vascular occlusion, haemodynamic changes nor survival of corticospinal neurons within the ipsilateral sensory-motor cortex in the acute stages of stroke. Instead, using a combination of tract tracing, electrical stimulation and functional connectivity mapping, we demonstrated that corticospinal axons originating from the contralateral side of the brain in mice administered gabapentin extend numerous collaterals, form new synaptic contacts and better integrate within spinal circuits that control forelimb muscles. Not only does gabapentin daily administration promote neuroplasticity, but it also dampens maladaptive plasticity by reducing the excitability of spinal motor circuitry. In turn, mice administered gabapentin starting 1 h or 1 day after stroke recovered skilled upper extremity function. Functional recovery persists even after stopping the treatment at 6 weeks following a stroke. Finally, chemogenetic silencing of cortical projections originating from the contralateral side of the brain transiently abrogated recovery in mice administered gabapentin, further supporting the conclusion that gabapentin-dependent reorganization of spared cortical pathways drives functional recovery after stroke. These observations highlight the strong potential for repurposing gabapentinoids as a promising treatment strategy for stroke repair.

Across the adult lifespan the ipsilateral sensorimotor cortex negative BOLD response exhibits decreases in magnitude and spatial extent suggesting declining inhibitory control

Ipsilateral sensorimotor (iSM1) cortex negative BOLD responses (NBR) are observed to unilateral tasks and are thought to reflect a functionally relevant component of sensorimotor inhibition. Evidence suggests that sensorimotor inhibitory mechanisms degrade with age, along with aspects of motor ability and dexterity. However, understanding of age-related changes to NBR is restricted by limited comparisons between young vs old adults groups with relatively small samples sizes. Here we analysed a BOLD fMRI dataset (obtained from the CamCAN repository) of 581 healthy subjects, gender-balanced, sampled from the whole adult lifespan performing a motor response task to an audiovisual stimulus. We aimed to investigate how sensorimotor and default-mode NBR characteristics of magnitude, spatial extent and response shape alter at every decade of the aging process. We observed a linear decrease in iSM1 NBR magnitude across the whole lifespan, whereas the contralateral sensorimotor (cSM1) PBR magnitude was unchanged. An age-related decrease in the spatial extent of NBR and an increase in the ipsilateral positive BOLD response (PBR) was observed. This occurred alongside an increasing negative correlation between subject's iSM1 NBR and cSM1 PBR magnitude, reflecting a change in the balance between cortical excitation and inhibition. Conventional GLM analysis, using a canonical haemodynamic response (HR) function, showed disappearance of iSM1 NBR in subjects over 50 years of age. However, a deconvolution analysis showed that the shape of the iSM1 HR altered throughout the lifespan, with significantly delayed time-to-peak and decreased magnitude. The most significant decreases in iSM1 HR magnitude occurred in older age (>60 years) but the first changes in HR shape and timing occurred as early as 30 years, suggesting the possibility of separate mechanisms underlying these alterations. Reanalysis using data-driven HRs for each decade detected significant sensorimotor NBR into late older age, showing the importance of taking changes in HR morphology into account in fMRI aging studies. These results may reflect fMRI measures of the age-related decreases in transcollosal inhibition exerted upon ipsilateral sensorimotor cortex and alterations to the excitatory-inhibitory balance in the sensorimotor network.

Comparing between Different Sets of Preprocessing, Classifiers, and Channels Selection Techniques to Optimise Motor Imagery Pattern Classification System from EEG Pattern Recognition

The ability to control external devices through thought is increasingly becoming a reality. Human beings can use the electrical signals of their brain to interact or change the surrounding environment and more. The development of this technology called brain-computer interface (BCI) will increasingly allow people with motor disabilities to communicate or use assistive devices to walk, manipulate objects and communicate. Using data from the PhysioNet database, this study implemented a pattern classification system for use in a BCI on 109 healthy volunteers during real movement activities and motor imagery recorded by 64-channels electroencephalography (EEG) system. Different classifiers such as Support Vector Machine (SVM), K-Nearest Neighbors (KNN), and Decision Trees (TREE) were applied on different combinations of EEG channels. Starting from two channels (C3, C4 and CP3 and CP4) positioned on the contralateral and ipsilateral sensorimotor cortex, the Region of Interest (RoI) centred on C3/Cp3 and C4/Cp4 and, finally, a data-driven automatic channels selection was tested to explore the best channel combination able to increase the classification accuracy. The results showed that the proposed automatic channels selection was able to significantly improve the performance of each classifier achieving 98% of accuracy for classification of real and imagined hand movement (sensitivity = 97%, specificity = 99%, AUC = 0.99) by SVM. While the accuracy of the classification between the imagery of hand and foot movements was 91% (sensitivity = 87%, specificity = 86%, AUC = 0.93) also with SVM. In the proposed approach, the data-driven automatic channels selection outperforms classical a priori channel selection models such as C3/C4, Cp3/Cp4, or RoIs around those channels with the utmost accuracy to help remove the boundaries of human communication and improve the quality of life of people with disabilities.

A Single Bout of High-Intensity Cardiovascular Exercise Does Not Enhance Motor Performance and Learning of a Visuomotor Force Modulation Task, but Triggers Ipsilateral Task-Related EEG Activity.

Acute cardiovascular exercise (aCE) seems to be a promising strategy to improve motor performance and learning. However, results are heterogeneous, and the related neurophysiological mechanisms are not well understood. Oscillatory brain activitiy, such as task-related power (TRPow) in the alpha and beta frequencies, are known neural signatures of motor activity. Here, we tested the effects of aCE on motor performance and learning, along with corresponding modulations in EEG TRPow over the sensorimotor cortex. Forty-five right-handed participants (aged 18–34 years) practiced a visuomotor force-matching (FM) task after either high-intensity (HEG), low-intensity (LEG), or no exercise (control group, CG). Motor performance was assessed immediately, 15 min, 30 min, and 24 h after aCE/control. EEG was measured during the FM task. Results of frequentist and Bayesian statistics revealed that high- and low-intensity aCE had no effect at the behavioral level, adding to the previous mixed results. Interestingly, EEG analyses showed an effect of aCE on the ipsilateral sensorimotor cortex, with a stronger decrease in β-TRPow 15 min after exercise in both groups compared to the CG. Overall, aCE applied before motor practice increased ipsilateral sensorimotor activity, while motor learning was not affected; it remains to be seen whether aCE might affect motor learning in the long run.

Distinct representation of ipsilateral hand movements in sensorimotor areas

There is ample evidence that the contralateral sensorimotor areas play an important role in movement generation, with the primary motor cortex and the primary somatosensory cortex showing a detailed spatial organization of the representation of contralateral body parts. Interestingly, there are also indications for a role of the motor cortex in controlling the ipsilateral side of the body. However, the precise function of ipsilateral sensorimotor cortex in unilateral movement control is still unclear. Here, we show hand movement representation in the ipsilateral sensorimotor hand area, in which hand gestures can be distinguished from each other and from contralateral hand gestures. High‐field functional magnetic resonance imaging (fMRI) data acquired during the execution of six left‐ and six right‐hand gestures by healthy volunteers showed ipsilateral activation mainly in the anterior section of precentral gyrus and the posterior section of the postcentral gyrus. Despite the lower activation in ipsilateral areas closer to the central sulcus, activity patterns for the 12 hand gestures could be mutually distinguished in these areas. The existence of a unique representation of ipsilateral hand movements in the human sensorimotor cortex favours the notion of transcallosal integrative processes that support optimal coordination of hand movements.

Changes of cerebral network activity after invasive stimulation of the mesencephalic locomotor region in a rat stroke model

Motor deficits after stroke reflect both, focal lesion and network alterations in brain regions distant from infarction. This remote network dysfunction may be caused by aberrant signals from cortical motor regions travelling via mesencephalic locomotor region (MLR) to other locomotor circuits. A method for modulating disturbed network activity is deep brain stimulation. Recently, we have shown that high frequency stimulation (HFS) of the MLR in rats has restored gait impairment after photothrombotic stroke (PTS). However, it remains elusive which cerebral regions are involved by MLR-stimulation and contribute to the improvement of locomotion. Seventeen male Wistar rats underwent photothrombotic stroke of the right sensorimotor cortex and implantation of a microelectrode into the right MLR. 2-[18F]Fluoro-2-deoxyglucose ([18F]FDG)-positron emission tomography (PET) was conducted before stroke and thereafter, on day 2 and 3 after stroke, without and with MLR-HFS, respectively. [18F]FDG-PET imaging analyses yielded a reduced glucose metabolism in the right cortico-striatal thalamic loop after PTS compared to the state before intervention. When MLR-HFS was applied after PTS, animals exhibited a significantly higher uptake of [18F]FDG in the right but not in the left cortico-striatal thalamic loop. Furthermore, MLR-HFS resulted in an elevated glucose metabolism of right-sided association cortices related to the ipsilateral sensorimotor cortex. These data support the concept of diaschisis i.e., of dysfunctional brain areas distant to a focal lesion and suggests that MLR-HFS can reverse remote network effects following PTS in rats which otherwise may result in chronic motor symptoms.

Decoding attempted phantom hand movements from ipsilateral sensorimotor areas after amputation

Objective. The sensorimotor cortex is often selected as target in the development of a Brain-Computer Interface, as activation patterns from this region can be robustly decoded to discriminate between different movements the user executes. Up until recently, such BCIs were primarily based on activity in the contralateral hemisphere, where decoding movements still works even years after denervation. However, there is increasing evidence for a role of the sensorimotor cortex in controlling the ipsilateral body. The aim of this study is to investigate the effects of denervation on the movement representation on the ipsilateral sensorimotor cortex. Approach. Eight subjects with acquired above-elbow arm amputation and nine controls performed a task in which they made (or attempted to make with their phantom hand) six different gestures from the American Manual Alphabet. Brain activity was measured using 7T functional MRI, and a classifier was trained to discriminate between activation patterns on four different regions of interest (ROIs) on the ipsilateral sensorimotor cortex. Main results. Classification scores showed that decoding was possible and significantly better than chance level for both the phantom and intact hands from all ROIs. Decoding both the left (intact) and right (phantom) hand from the same hemisphere was also possible with above-chance level classification score. Significance. The possibility to decode both hands from the same hemisphere, even years after denervation, indicates that implantation of motor-electrodes for BCI control possibly need only cover a single hemisphere, making surgery less invasive, and increasing options for people with lateralized damage to motor cortex like after stroke.

Towards chronic deep brain stimulation in freely moving hemiparkinsonian rats: applicability and functionality of a fully implantable stimulation system

Objective. This study aimed at investigating a novel fully implantable deep brain stimulation (DBS) system and its ability to modulate brain metabolism and behavior through subthalamic nucleus (STN) stimulation in a hemiparkinsonian rat model. Approach. Twelve male rats were unilaterally lesioned with 6-hydroxydopamine in the medial forebrain bundle and received a fully implantable DBS system aiming at the ipsilesional STN. Each rat underwent three cylinder tests to analyze front paw use: a PRE test before any surgical intervention, an OFF test after surgery but before stimulation onset and an ON test under DBS. To visualize brain glucose metabolism in the awake animal, two [18F]FDG scans were conducted in the OFF and ON condition. At least 4 weeks after surgery, an [18F]FDOPA scan was used to check for dopaminergic integrity. Main results. In general, STN DBS increased [18F]FDG uptake ipsilesionally and decreased it contralesionally. More specifically, bilateral orbitofrontal cortex, ipsilateral caudate putamen, sensorimotor cortex and nucleus accumbens showed significantly higher tracer uptake in ON compared to OFF condition. Contralateral cingulate and secondary motor cortex, caudate putamen, amygdala, hippocampus, retrosplenial granular cortex, superior colliculus, and parts of the cerebellum exhibited significantly higher [18F]FDG uptake in the OFF condition. On the behavioral level, stimulation was able improve use of the contralesional affected front paw suggesting an effective stimulation produced by the implanted system. Significance. The fully implantable stimulation system developed by us and presented here offers the output of arbitrary user-defined waveforms, patterns and stimulation settings and allows tracer accumulation in freely moving animals. It is therefore a suitable device for implementing behavioral PET studies. It contributes immensely to the possibilities to characterize and unveil the effects and mechanisms of DBS offering valuable clues for future improvements of this therapy.

Examination of the development and aging of brain deactivation using a unimanual motor task

In the central nervous system, regional neuronal inhibition plays important roles in functional segregation. Here, we showed how brain deactivation, which is a putative index of neuronal inhibition, develops and ages using a unimanual motor task. Healthy right-handed children (8–11 years), adolescents (12–15 years), young adults (20–24 years), and older adults (69–75 years; 21 participants in each group) underwent functional magnetic resonance imaging with their eyes closed while they performed 1-Hz alternating extension–flexion of the right wrist. In young adults, we found deactivations in the hand/arm section of the ipsilateral primary sensorimotor cortices (SM1) including the dorsal premotor cortex (interhemispheric inhibition), foot and face SM1 sections (cross-somatotopic inhibition), visual and auditory cortices (cross-modal inhibition), and precuneus and medial prefrontal cortex of the default mode network (DMN; DMN inhibition). Interhemispheric, cross-modal, and DMN inhibitions developed from childhood to adulthood, but cross-somatotopic inhibition showed no developmental changes. Conversely, interhemispheric, cross-somatotopic, and cross-modal inhibitions, but not DMN inhibition, decreased with aging. Thus, neuronal inhibition generally progresses with development and deteriorates with aging, with some noted regional differences. This was the first study to systematically describe the development and aging of brain deactivation, which may reflect regional neuronal inhibition.

Constraint-induced movement therapy enhances AMPA receptor-dependent synaptic plasticity in the ipsilateral hemisphere following ischemic stroke.

Constraint-induced movement therapy (CIMT) can promote the recovery of motor function in injured upper limbs following stroke, which may be associated with upregulation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) at synapses in the ipsilateral sensorimotor cortex in our previous study. However, AMPAR distribution is tightly regulated, and only AMPARs on the postsynaptic membrane can mediate synaptic transmission. We speculated that synaptic remodeling induced by movement-associated synaptic activity can promote functional recovery from stroke. To test this hypothesis, we compared AMPAR expression on the postsynaptic membrane surface in a rat model of ischemic stroke induced by middle cerebral artery occlusion (MCAO) with versus without CIMT, which consisted of daily running wheel training for 2 weeks starting on day 7 after MCAO. The results showed that CIMT increased the number of glutamate receptor (GluR)2-containing functional synapses in the ipsilateral sensorimotor cortex, and reduced non-GluR2 AMPARs in the ipsilateral sensorimotor cortex and hippocampal CA3 region. In addition, CIMT enhanced AMPAR expression on the surface of post-synaptic membrane in the ipsilateral sensorimotor cortex and hippocampus. Thus, CIMT promotes the recovery of motor function of injured upper limbs following stroke by enhancing AMPAR-mediated synaptic transmission in the ischemic hemisphere. These findings provide supporting evidence for the clinical value of CIMT for restoring limb movement in stroke patients. All experimental procedures and protocols were approved by the Department of Laboratory Animal Science of Fudan University, China (approval No. 201802173S) on March 3, 2018.

Age-related trends in neuromagnetic transient beta burst characteristics during a sensorimotor task and rest in the Cam-CAN open-access dataset

Non-invasive neurophysiological recordings, such as those measured by magnetoencelography (MEG), provide insight into the behaviour of neural networks and how these networks change with factors such as task performance, disease state, and age. Recently, there has been a trend in describing neurophysiological recordings as a series of transient bursts of neural activity rather than averaged sustained oscillations as burst characteristics may be more directly correlated with the neurological generators of brain activity. In this work, we investigate how beta burst characteristics change with age in a large open access dataset. The objectives are (1) to detect and characterize transient beta bursts over the ipsilateral and contralateral primary sensorimotor cortices during a unilateral motor task performance and during wakeful resting, and (2) to identify age-related changes in beta burst characteristics, in the context of earlier reports of age-related changes in beta suppression and the post-movement beta rebound. MEG data, acquired at the Cambridge Centre for Ageing and Neuroscience, of roughly 600 participants with a nearly uniform distribution of ages between 18 and 88 years old was used for analysis. We found that burst rate is the predominant factor related to age-related changes in the amplitude of the induced beta rhythm responses associated with a button press task. Furthermore, we present a cross-validation of burst parameters detected at the sensor- (peak sensor and sensor ROI) and source-level (beamformer spatial filter). This work is as an important step in characterizing transient bursts in neuromagnetic signals in the temporal domain, towards a better understanding of the healthy aging human brain.

The cortical oscillatory patterns associated with varying levels of reward during an effortful vigilance task

We explored how reward and value of effort shapes performance in a sustained vigilance, reaction time (RT) task. It was posited that reward and value would hasten RTs and increase cognitive effort by boosting activation in the sensorimotor cortex and inhibition in the frontal cortex, similar to the horse-race model of motor actions. Participants performed a series of speeded responses while expecting differing monetary rewards (0 pence (p), 1 p, and 10 p) if they responded faster than their median RT. Amplitudes of cortical alpha, beta, and theta oscillations were analysed using the event-related desynchronization method. In experiment 1 (N = 29, with 12 females), reward was consistent within block, while in experiment 2 (N = 17, with 12 females), reward amount was displayed before each trial. Each experiment evaluated the baseline amplitude of cortical oscillations differently. The value of effort was evaluated using a cognitive effort discounting task (COGED). In both experiments, RTs decreased significantly with higher rewards. Reward level sharpened the increased amplitudes of beta oscillations during fast responses in experiment 1. In experiment 2, reward decreased the amplitudes of beta oscillations in the ipsilateral sensorimotor cortex. Individual effort values did not significantly correlate with oscillatory changes in either experiment. Results suggest that reward level and response speed interacted with the task- and baseline-dependent patterns of cortical inhibition in the frontal cortex and with activation in the sensorimotor cortex during the period of motor preparation in a sustained vigilance task. However, neither the shortening of RT with increasing reward nor the value of effort correlated with oscillatory changes. This implies that amplitudes of cortical oscillations may shape upcoming motor responses but do not translate higher-order motivational factors into motor performance.

Early Exercise after Intracerebral Hemorrhage Inhibits Inflammation and Promotes Neuroprotection in the Sensorimotor Cortex in Rats

The present study examined the effect of early exercise on brain damage and recovery of motor function following intracerebral hemorrhage (ICH) in rats. Subjects were randomly assigned to no training after ICH (ICH), no training after sham surgery (SHAM), early treadmill exercise after ICH (ICH + ET), and late treadmill exercise after ICH (ICH + LT) groups. The ICH + ET and ICH + LT groups were trained for seven consecutive days starting on day 2 and day 9 after surgery, respectively. At post surgery day 16, the brain was surgically excised, and lesion volume, cortical thickness, neuronal number, dendritic length, and dendritic complexity were analyzed. Expression levels of IL-1b, TGF-b1, and IGF-1 mRNAs in ipsilateral sensorimotor cortex were measured by RT-PCR. The recovery of motor function in the ICH + ET group was the most accelerated. Cortical thickness and neuronal number were significantly higher in the ICH + ET group than the ICH and ICH + LT groups. The length and complexity of dendrites were also significantly greater in the ICH + ET group compared with the ICH and ICH + LT groups. Expression of IL-1b mRNA was significantly lower in the ICH + ET group than that in the ICH group. Collectively, these results suggest that early treadmill exercise after ICH promotes recovery of sensorimotor function by preventing neuronal death and ensuing cortical atrophy and by preserving dendritic structure compared with late treadmill exercise and no exercise. Early exercise may prevent neurodegeneration and functional loss by inhibiting neuroinflammation.

Constraint-induced movement therapy improves functional recovery after ischemic stroke and its impacts on synaptic plasticity in sensorimotor cortex and hippocampus

Constraint-induced movement therapy (CIMT) has proven to be an effective way to restore functional deficits following stroke in human and animal studies, but its underlying neural plasticity mechanism remains unknown. Accumulating evidence indicates that rehabilitation after stroke is closely associated with synaptic plasticity. We therefore investigated the impact of CIMT on synaptic plasticity in ipsilateral and contralateral brain of rats following stroke. Rats were subjected to 90 minutes of transient middle cerebral artery occlusion (MCAO). CIMT was performed from 7 days after stroke and lasted for two weeks. Modified Neurology Severity Score (mNSS) and the ladder rung walking task tests were conducted at 7,14 and 21 days after stroke. Golgi-Cox staining was used to observe the plasticity changes of dendrites and dendritic spines. The expression of glutamate receptors (GluR1, GluR2 and NR1) were examined by western blot. Our data suggest that the dendrites and dendritic spines are damaged to varying degrees in bilateral sensorimotor cortex and hippocampus after acute stroke. CIMT treatment enhances the plasticity of dendrites and dendritic spines in the ipsilateral and contralateral sensorimotor cortex, increases the expression of synaptic GluR2 in ipsilateral sensorimotor cortex, which may be mechanisms for CIMT to improve functional recovery after ischemic stroke.