The supplementary motor area modulates interhemispheric interactions during movement preparation

Functional Connectivity Profiles of Ten Sub-Regions within the Premotor and Supplementary Motor Areas: Insights into Neurophysiological Integration

Objectives: This study aimed to comprehensively investigate the functional connectivity of ten sub-regions within the premotor and supplementary motor areas (Right and Left Premotor 6d1, 6d2, 6d3, and Right and Left pre-Supplementary Motor (presma) and SMA). Using advanced magnetic resonance imaging (MRI), the objective was to understand the neurophysiological integrative characteristics of these regions by examining their connectivity with eight distinct functional brain networks. While previous studies have largely treated these areas as homogeneous entities, there is a significant gap in our understanding of the specific roles and connectivity profiles of their distinct sub-regions. The goal was to uncover the roles of these regions beyond conventional motor functions, contributing to a more holistic understanding of brain functioning. Methods: The study involved 198 healthy volunteers, with the primary methodology being functional connectivity analysis using advanced MRI techniques. Ten sub-regions within the premotor and supplementary motor areas served as seed regions, and their connectivity with eight distinct brain regional functional networks, including the Sensorimotor, Dorsal Attention, Language, Frontoparietal, Default Mode, Cerebellar, Visual, and Salience networks, was investigated. This approach allowed for the exploration of synchronized activity between these critical brain areas, shedding light on their integrated functioning and relationships with other brain networks. Results: The study revealed a nuanced landscape of functional connectivity for the premotor and supplementary motor areas with the main functional brain networks. Despite their high functional connectedness within the motor network, these regions displayed diverse functional integrations with other networks. There was moderate connectivity with the Sensorimotor and Dorsal Attention networks, highlighting their roles in motor execution and attentional processes. However, connectivity with the Language, Frontoparietal, Default Mode, Cerebellar, Visual, and Salience networks was generally low, indicating a primary focus on motor-related tasks. Conclusions: This study emphasized the multifaceted roles of the sub-regions of the premotor and supplementary motor areas. Beyond their crucial involvement in motor functions, these regions exhibited varied functional integrations with different brain networks. The observed disparities, especially in the Sensorimotor and Dorsal Attention networks, indicated a nuanced and specialized involvement of these regions in diverse cognitive functions. By delineating the specific connectivity profiles of these sub-regions, this study addresses the existing knowledge gap and suggests unique and distinct roles for each brain area in sophisticated cognitive tasks beyond their conventional motor functions. The results suggested unique and distinct roles for each brain area in sophisticated cognitive tasks beyond their conventional motor functions. This study underscores the importance of considering the broader neurophysiological landscape to comprehend the intricate roles of these brain areas, contributing to ongoing efforts in unravelling the complexities of brain function.

Test-retest reliability of intrahemispheric dorsal premotor and primary motor cortex dual-site TMS connectivity measures

OBJECTIVE

Investigating the optimal interstimulus interval (ISI) and the 24-hour test-retest reliability for intrahemispheric dorsal premotor cortex (PMd) - primary motor cortex (M1) connectivity using dual-site transcranial magnetic stimulation (dsTMS).

METHODS

In 21 right-handed adults, left intrahemispheric PMd-M1 connectivity has been investigated with a stacked-coil dsTMS setup (conditioning stimulus: 75% of resting motor threshold; test stimulus: eliciting MEPs of 1-1.5 mV) at ISIs of 3, 5-8, and 10 ms. Additionally, M1-M1 short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were investigated to assess comparability to standard paired-pulse setups.

RESULTS

Conditioning PMd led to significant inhibition of M1 output at ISIs of 3 and 5 ms, whereas 10 ms resulted in facilitation (all, p < 0.001), with a fair test-retest reliability for 3 (ICC: 0.47) and 6 ms (ICC: 0.44) ISIs. Replication of SICI (p < 0.001) and ICF (p = 0.017) was successful, with excellent test-retest reliability for SICI (ICC: 0.81).

CONCLUSION

This dsTMS setup can probe the inhibitory and facilitatory PMd-M1 connections, as well as reliably replicate SICI and ICF paradigms.

SIGNIFICANCE

The stacked-coil dsTMS setup for investigating intrahemispheric PMd-M1 connectivity offers promising possibilities to better understand motor control.

Aberrant connectivity of the lateralized readiness system in non-syndromic congenital mirror movements

OBJECTIVES

Non-syndromic CMM has a complex phenotype. Abnormal corpus callosum and corticospinal tract processes are suggested mechanisms of the mirror movements. To further explore behavioural and neural phenotype(s) the present study tests the hypothesis that the response readiness network comprising supplementary motor area (SMA) and connections with motor cortex (M1) functions abnormally in CMM.

METHODS

Twelve participants with (non-syndromic) CMM and a control group (n = 28) were tested on a probabilistic Go-NoGo task while electroencephalography (EEG) was recorded to assess possible group differences in lateralized readiness of voluntary hand movements together with measures of SMA-M1 functional connectivity.

RESULTS

The CMM group demonstrated delayed lateralized readiness and stronger functional connectivity between left-brain SMA-M1 regions. Connectivity strength was correlated with measures of behavioural performance but not with extent of mirroring.

CONCLUSIONS

Abnormalities in brain processes upstream of movement output likely reflect neurocompensation as a result of lifelong experience with mirroring in CMM.

SIGNIFICANCE

These findings extend the known neural abnormalities in CMM to include brain networks upstream from those involved in motor output and raise the question of whether neurocompensatory plasticity might be involved.

[Paresis of an upper extremity. Action observation and motor imagery in recovery of patients with chronic stroke]

INTRODUCTION

Action observation (AO) and motor imagery (MI) are considered functionally equivalent forms of motor representation related to movement execution (ME). Because of their characteristics, AO and MI have been proposed as techniques to facilitate the recovery of post-stroke hemiparesis in the upper extremities.

PATIENTS AND METHODS

An experimental, longitudinal, prospective, single-blinded design was undertaken. Eleven patients participated, and were randomly assigned to each study group. Both groups received 10 to 12 sessions of physical therapy. Five patients were assigned to the control treatment group, and six patients to the experimental treatment group (AO + MI). All were assessed before and after treatment for function, strength (newtons) and mobility (percentage) in the affected limb, as well as alpha desynchronisation (8-13 Hz) in the supplementary motor area, the premotor cortex and primary motor cortex while performing AO + MI tasks and action observation plus motor execution (AO + ME).

RESULTS

The experimental group presented improvement in function and strength. A negative correlation was found between desynchronisation in the supplementary motor area and function, as well as a post-treatment increase in desynchronisation in the premotor cortex of the injured hemisphere in the experimental group only.

CONCLUSIONS

An AO + MI-based intervention positively impacts recovery of the paretic upper extremity by stimulating the supplementary motor area, a cortex involved in movement preparation and learning. AO + MI therapy can be used as adjunctive treatment in patients with upper extremity paresis following chronic stroke.

Bilateral intracortical inhibition during unilateral motor preparation and sequence learning

Motor sequence learning gradually quickens reaction time, suggesting that sequence learning alters motor preparation processes. Interestingly, evidence has shown that preparing sequence movements decreases short intracortical inhibition (SICI) in the contralateral motor cortex (M1), but also that sequence learning alters motor preparation processes in both the contralateral and ipsilateral M1s. Therefore, one possibility is that sequence learning alters the SICI decreases occurring during motor preparation in bilateral M1s. To examine this, two novel hypotheses were tested: unilateral sequence preparation would decrease SICI in bilateral M1s, and sequence learning would alter such bilateral SICI responses. Paired-pulse transcranial magnetic stimulation was delivered over the contralateral and ipsilateral M1s to assess SICI in an index finger muscle during the preparation of sequences initiated by either the right index or little finger. In the absence of sequence learning, SICI decreased in both the contralateral and ipsilateral M1s during the preparation of sequences initiated by the right index finger, suggesting that SICI decreases in bilateral M1s during unilateral motor preparation. As sequence learning progressed, SICI decreased in the contralateral M1 whilst it increased in the ipsilateral M1. Moreover, these bilateral SICI responses were observed at the onset of motor preparation, suggesting that sequence learning altered baseline SICI levels rather than the SICI decreases occurring during motor preparation per se. Altogether, these results suggest that SICI responses in bilateral M1s reflect two motor processes: an acute decrease of inhibition during motor preparation, and a cooperative but bidirectional shift of baseline inhibition levels as sequence learning progresses.

Multifaceted neural and vascular pathologies after pediatric mild traumatic brain injury

Dynamic changes in neurodevelopment and cognitive functioning occur during adolescence, including a switch from reactive to more proactive forms of cognitive control, including response inhibition. Pediatric mild traumatic brain injury (pmTBI) affects these cognitions immediately post-injury, but the role of vascular versus neural injury in cognitive dysfunction remains debated. This study consecutively recruited 214 sub-acute pmTBI (8-18 years) and age/sex-matched healthy controls (HC; N = 186), with high retention rates (>80%) at four months post-injury. Multimodal imaging (functional MRI during response inhibition, cerebral blood flow and cerebrovascular reactivity) assessed for pathologies within the neurovascular unit. Patients exhibited increased errors of commission and hypoactivation of motor circuitry during processing of probes. Evidence of increased/delayed cerebrovascular reactivity within motor circuitry during hypercapnia was present along with normal perfusion. Neither age-at-injury nor post-concussive symptom load were strongly associated with imaging abnormalities. Collectively, mild cognitive impairments and clinical symptoms may continue up to four months post-injury. Prolonged dysfunction within the neurovascular unit was observed during proactive response inhibition, with preliminary evidence that neural and pure vascular trauma are statistically independent. These findings suggest pmTBI is characterized by multifaceted pathologies during the sub-acute injury stage that persist several months post-injury.

Effects of non-invasive brain stimulation over supplementary motor area in people with Parkinson's disease: a protocol for a systematic review and meta-analysis of randomised controlled trials

INTRODUCTION

Individuals with Parkinson's disease (PD) often experience initial hesitation, slowness of movements, decreased balance and impaired standing ability, which can significantly impact their independence. Transcranial magnetic stimulation and transcranial direct current stimulation are two widely used and promising non-invasive brain stimulation (NIBS) modalities for treating PD. The supplementary motor area (SMA), associated with motor behaviour and processing, has received increasing attention as a potential stimulation target to alleviate PD-related symptoms. However, the data on NIBS over SMA in PD individuals are inconsistent and has not been synthesised. In this article, we will review the evidence for NIBS over SMA in PD individuals and evaluate its efficacy in improving PD function.

METHOD AND ANALYSIS

Randomised controlled clinical trials comparing the effects of NIBS and sham stimulation on motor function, activities of daily living and participation for people with PD will be included. A detailed computer-aided search of the literature will be performed from inception to February 2023 in the following databases: PubMed, EMBASE, Physiotherapy Evidence Database (PEDro), Web of Science (WOS) and The Chinese National Knowledge Infrastructure (CNKI). Two independent reviewers will screen articles for relevance and methodological validity. The PEDro scale will be used to evaluate the risk of bias of selected studies. Data from included studies will be extracted by two independent reviewers through a customised, preset data extraction sheet.

ETHICS AND DISSEMINATION

Ethical approval is not required for this systematic review. The study's findings will be presented at scientific meetings and published in peer-reviewed journals.

PROSPERO REGISTRATION NUMBER

CRD42023399945.

Mapping of the supplementary motor area using repetitive navigated transcranial magnetic stimulation

Background

The supplementary motor area (SMA) is important for motor and language function. Damage to the SMA may harm these functions, yet tools for a preoperative assessment of the area are still sparse.

Objective

The aim of this study was to validate a mapping protocol using repetitive navigated transcranial magnetic stimulation (rnTMS) and extend this protocol for both hemispheres and lower extremities.

Methods

To this purpose, the SMA of both hemispheres were mapped based on a finger tapping task for 30 healthy subjects (35.97 ± 15.11, range 21-67 years; 14 females) using rnTMS at 20 Hz (120% resting motor threshold (RMT)) while controlling for primary motor cortex activation. Points with induced errors were marked on the corresponding MRI. Next, on the identified SMA hotspot a bimanual finger tapping task and the Nine-Hole Peg Test (NHPT) were performed. Further, the lower extremity was mapped at 20 Hz (140%RMT) using a toe tapping task.

Results

Mean finger tapping scores decreased significantly during stimulation (25.70taps) compared to baseline (30.48; p < 0.01). Bimanual finger tapping led to a significant increase in taps during stimulation (28.43taps) compared to unimanual tapping (p < 0.01). Compared to baseline, completion time for the NHPT increased significantly during stimulation (baseline: 13.6 s, stimulation: 16.4 s; p < 0.01). No differences between hemispheres were observed.

Conclusion

The current study validated and extended a rnTMS based protocol for the mapping of the SMA regarding motor function of upper and lower extremity. This protocol could be beneficial to better understand functional SMA organisation and improve preoperative planning in patients with SMA lesions.

Analysis of functional connectivity using machine learning and deep learning in different data modalities from individuals with schizophrenia

Objective. Schizophrenia(SCZ) is a severe mental disorder associated with persistent or recurrent psychosis, hallucinations, delusions, and thought disorders that affect approximately 26 million people worldwide, according to the World Health Organization. Several studies encompass machine learning (ML) and deep learning algorithms to automate the diagnosis of this mental disorder. Others study SCZ brain networks to get new insights into the dynamics of information processing in individuals suffering from the condition. In this paper, we offer a rigorous approach with ML and deep learning techniques for evaluating connectivity matrices and measures of complex networks to establish an automated diagnosis and comprehend the topology and dynamics of brain networks in SCZ individuals.Approach.For this purpose, we employed an functional magnetic resonance imaging (fMRI) and electroencephalogram (EEG) dataset. In addition, we combined EEG measures, i.e. Hjorth mobility and complexity, with complex network measurements to be analyzed in our model for the first time in the literature.Main results.When comparing the SCZ group to the control group, we found a high positive correlation between the left superior parietal lobe and the left motor cortex and a positive correlation between the left dorsal posterior cingulate cortex and the left primary motor. Regarding complex network measures, the diameter, which corresponds to the longest shortest path length in a network, may be regarded as a biomarker because it is the most crucial measure in different data modalities. Furthermore, the SCZ brain networks exhibit less segregation and a lower distribution of information. As a result, EEG measures outperformed complex networks in capturing the brain alterations associated with SCZ.Significance. Our model achieved an area under receiver operating characteristic curve (AUC) of 100% and an accuracy of 98.5% for the fMRI, an AUC of 95%, and an accuracy of 95.4% for the EEG data set. These are excellent classification results. Furthermore, we investigated the impact of specific brain connections and network measures on these results, which helped us better describe changes in the diseased brain.

Cortico-striatal activity associated with fidget spinner use: an fMRI study

Fidget spinners are said to be a very successful toy, and it's said that it has a good impact on attention for children with ADHD and hand motor control. However, there is limited scientific evidence to support these claims, and there is a lack of data on neurobiological responses to rotating fidget spinners. To better understand the mechanism whereby fidget spinners affect motor behavior, we tried to identify the neural correlates of rotating fidget spinners using functional magnetic resonance imaging and non-magnetic fidget spinners with five types of ease of rotation. As a result, we confirmed that the pre/postcentral gyrus, middle temporal gyrus, supplementary motor area (SMA), cerebellum, and striatum are activated when rotating spinners. Furthermore, the SMA was activated more with easier-to-rotate spinners. Additionally, a psychophysiological interaction analysis revealed increased functional connectivity between the SMA and the caudate while rotating fidget spinners compared to just holding them. These results suggest that the fine motor control associate with spinning a fidget spinner is supported by the cortico-striatal circuits involved in planning and reward.

PMd and action preparation: bridging insights between TMS and single neuron research

Transcranial magnetic stimulation (TMS) research has furthered understanding of human dorsal premotor cortex (PMd) function due to its unrivalled ability to measure the inhibitory and facilitatory influences of PMd over the primary motor cortex (M1) in a temporally precise manner. TMS research indicates that PMd transiently modulates inhibitory output to effector representations within M1 during motor preparation, with the direction of modulation depending on which effectors are selected for response, and the timing of modulations co-varying with task selection demands. In this review, we critically assess this literature in the context of a dynamical systems approach used to model nonhuman primate (NHP) PMd/M1 single-neuron recordings during action preparation. Through this process, we identify gaps in the literature and propose future experiments.

Dynamic involvement of premotor and supplementary motor areas in bimanual pinch force control

Many activities of daily living require quick shifts between symmetric and asymmetric bimanual actions. Bimanual motor control has been mostly studied during continuous repetitive tasks, while little research has been carried out in experimental settings requiring dynamic changes in motor output generated by both hands. Here, we performed functional magnetic resonance imaging (MRI) while healthy volunteers performed a visually guided, bimanual pinch force task. This enabled us to map functional activity and connectivity of premotor and motor areas during bimanual pinch force control in different task contexts, requiring mirror-symmetric or inverse-asymmetric changes in discrete pinch force exerted with the right and left hand. The bilateral dorsal premotor cortex showed increased activity and effective coupling to the ipsilateral supplementary motor area (SMA) in the inverse-asymmetric context compared to the mirror-symmetric context of bimanual pinch force control while the SMA showed increased negative coupling to visual areas. Task-related activity of a cluster in the left caudal SMA also scaled positively with the degree of synchronous initiation of bilateral pinch force adjustments, irrespectively of the task context. The results suggest that the dorsal premotor cortex mediates increasing complexity of bimanual coordination by increasing coupling to the SMA while SMA provides feedback about motor actions to the sensory system.

Recent advances in treatment of spatial neglect: networks and neuropsychology

INTRODUCTION

Spatial neglect remains an underdiagnosed and undertreated consequence of stroke that imposes significant disability. A growing appreciation of brain networks involved in spatial cognition is helping us to develop a mechanistic understanding of different therapies under development.

AREAS COVERED

This review focuses on neuromodulation of brain networks for the treatment of spatial neglect after stroke, using evidence-based approaches including 1) Cognitive strategies that are more likely to impact frontal lobe executive function networks; 2) Visuomotor adaptation, which may depend on the integrity of parietal and parieto- and subcortical-frontal connections and the presence of a particular subtype of neglect labeled Aiming neglect; 3) Non-invasive brain stimulation that may modulate relative levels of activity of the two hemispheres and depend on corpus callosum connectivity; and 4) Pharmacological modulation that may exert its effect primarily via right-lateralized networks more closely involved in arousal.

EXPERT OPINION

Despite promising results from individual studies, significant methodological heterogeneity between trials weakened conclusions drawn from meta-analyses. Improved classification of spatial neglect subtypes will benefit research and clinical care. Understanding the brain network mechanisms of different treatments and different types of spatial neglect will make possible a precision medicine treatment approach.

A systematic review of the neurobiological effects of theta-burst stimulation (TBS) as measured using functional magnetic resonance imaging (fMRI)

Theta burst stimulation (TBS) is associated with the modulation of a range of clinical, cognitive, and behavioural outcomes, but specific neurobiological effects remain somewhat unclear. This systematic literature review investigated resting-state and task-based functional magnetic resonance imaging (fMRI) outcomes post-TBS in healthy human adults. Fifty studies that applied either continuous-or intermittent-(c/i) TBS, and adopted a pretest-posttest or sham-controlled design, were included. For resting-state outcomes following stimulation applied to motor, temporal, parietal, occipital, or cerebellar regions, functional connectivity generally decreased in response to cTBS and increased in response to iTBS, though there were some exceptions to this pattern of response. These findings are mostly consistent with the assumed long-term depression (LTD)/long-term potentiation (LTP)-like plasticity effects of cTBS and iTBS, respectively. Task-related outcomes following TBS were more variable. TBS applied to the prefrontal cortex, irrespective of task or state, also produced more variable responses, with no consistent patterns emerging. Individual participant and methodological factors are likely to contribute to the variability in responses to TBS. Future studies assessing the effects of TBS via fMRI must account for factors known to affect the TBS outcomes, both at the level of individual participants and of research methodology.

Repeated unilateral handgrip contractions alter functional connectivity and improve contralateral limb response times

In humans, motor learning is underpinned by changes in sensorimotor network functional connectivity (FC). Unilateral contractions increase FC in the ipsilateral primary motor cortex (M1) and supplementary motor area (SMA); areas involved in motor planning and execution of the contralateral hand. Therefore, unilateral contractions are a promising approach to augment motor performance in the contralateral hand. In a within-participant, randomized, cross-over design, 15 right-handed adults had two magnetic resonance imaging (MRI) sessions, where functional-MRI and MR-Spectroscopic Imaging were acquired before and after repeated right-hand contractions at either 5% or 50% maximum voluntary contraction (MVC). Before and after scanning, response times (RTs) were determined in both hands. Nine minutes of 50% MVC contractions resulted in decreased handgrip force in the contracting hand, and decreased RTs and increased handgrip force in the contralateral hand. This improved motor performance in the contralateral hand was supported by significant neural changes: increased FC between SMA-SMA and increased FC between right M1 and right Orbitofrontal Cortex. At a neurochemical level, the degree of GABA decline in left M1, left and right SMA correlated with subsequent behavioural improvements in the left-hand. These results support the use of repeated handgrip contractions as a potential modality for improving motor performance in the contralateral hand.

Alterations in Corticocortical Vestibular Network Functional Connectivity Are Associated with Decreased Balance Ability in Elderly Individuals with Mild Cognitive Impairment

The corticocortical vestibular network (CVN) plays an important role in maintaining balance and stability. In order to clarify the specific relationship between the CVN and the balance ability of patients with mild cognitive impairment (MCI), we recruited 30 MCI patients in the community. According to age and sex, they were 1:1 matched to 30 older adults with normal cognitive function. We evaluated balance ability and performed MRI scanning in the two groups of participants. We analyzed functional connectivity within the CVN based on the region of interest. Then, we performed a Pearson correlation analysis between the functional connection and the Berg Balance Scale scores. The research results show that compared with the control group, there were three pairs of functional connections (hMST_R−Premotor_R, PFcm_R−SMA_L, and hMST_L−VIP_R) that were significantly decreased in the CVNs of the MCI group (p < 0.05). Further correlation analysis showed that there was a significant positive correlation between hMST_R−Premotor_R functional connectivity and BBS score (r = 0.364, p = 0.004). The decline in balance ability and increase in fall risk in patients with MCI may be closely related to the change in the internal connection mode of the corticocortical vestibular network.

Beta rhythmicity in human motor cortex reflects neural population coupling that modulates subsequent finger coordination stability

Human behavior is not performed completely as desired, but is influenced by the inherent rhythmicity of the brain. Here we show that anti-phase bimanual coordination stability is regulated by the dynamics of pre-movement neural oscillations in bi-hemispheric primary motor cortices (M1) and supplementary motor area (SMA). In experiment 1, pre-movement bi-hemispheric M1 phase synchrony in beta-band (M1-M1 phase synchrony) was online estimated from 129-channel scalp electroencephalograms. Anti-phase bimanual tapping preceded by lower M1-M1 phase synchrony exhibited significantly longer duration than tapping preceded by higher M1-M1 phase synchrony. Further, the inter-individual variability of duration was explained by the interaction of pre-movement activities within the motor network; lower M1-M1 phase synchrony and spectral power at SMA were associated with longer duration. The necessity of cortical interaction for anti-phase maintenance was revealed by sham-controlled repetitive transcranial magnetic stimulation over SMA in another experiment. Our results demonstrate that pre-movement cortical oscillatory coupling within the motor network unknowingly influences bimanual coordination performance in humans after consolidation, suggesting the feasibility of augmenting human motor ability by covertly monitoring preparatory neural dynamics.

Local Alterations of Left Arcuate Fasciculus and Transcallosal White Matter Microstructure in Schizophrenia Patients with Medication-resistant Auditory Verbal Hallucinations: A Pilot Study

Auditory verbal hallucinations (AVH) in schizophrenia (SZ) have been associated with abnormalities of the left arcuate fasciculus and transcallosal white matter projections linking homologous language areas of both hemispheres. While most studies have used a whole-tract approach, here we focused on analyzing local alterations of the above-mentioned pathways in SZ patients suffering medication-resistant AVH. Fractional anisotropy (FA) was estimated along the left arcuate fasciculus and interhemispheric projections of the rostral and caudal corpus callosum. Then, potential associations between white matter tracts and SZ symptoms were explored by correlating local site-by-site FA values and AVH severity estimated via the Auditory Hallucinations Rating Scale (AHRS). Compared to a sample of healthy controls, SZ patients displayed lower FA values in the rostral portion of the left arcuate fasciculus, near the frontal operculum, and in the left and right lateral regions of the rostral portion of the transcallosal pathways. In contrast, SZ patients showed higher FA values than healthy controls in the medial portion of the latter transcallosal pathway and in the midsagittal section of the interhemispheric auditory pathway. Finally, significant correlations were found between local FA values in the left arcuate fasciculus and the severity of the AVH's attentional salience. Contributing to the study of associations between local white matter alterations of language networks and SZ symptoms, our findings highlight local alterations of white matter integrity in these pathways linking language areas in SZ patients with AVH. We also hypothesize a link between the left arcuate fasciculus and the attentional capture of AVH.

Mirror movements after bimanual intensive therapy in children with unilateral cerebral palsy: A randomized controlled trial

AIM

To investigate potential changes in mirror movements after Hand and Arm Bimanual Intensive Therapy Including Lower Extremity (HABIT-ILE) training in children with unilateral cerebral palsy (CP).

METHOD

Thirty-one children with unilateral CP (mean age 9 years 4 months, SD 4 years 3 months; range 5 years 4 months-17 years 3 months; 14 females, 17 males) were randomized to either a control or treatment group. After allocation, children were assessed three times: before (T1, baseline) and after (T2) a 2-week interval and again at 3 months after T1 (T3) as follow-up. Between T1 and T2, the treatment group received 90 hours of HABIT-ILE training, while the control group continued their customary treatment. Mirror movements were assessed in all children using the Woods and Teuber Scale, as well as the Assisting Hand Assessment, Pediatric Evaluation of Disability Inventory, and Canadian Occupational Performance Measure.

RESULTS

Repeated measures analysis of variance indicated a significant decrease in mirror movements in the more-affected (mean difference = 0.97; 95% confidence interval [CI] = 0.51-1.42; p < 0.001) and less-affected (mean difference = 0.71; 95% CI = 0.37-1.0; p < 0.001) hands of children after HABIT-ILE; these improvements were maintained at the 3-month follow-up. Moreover, the mirror movement changes observed at the second assessment (T2) were inversely correlated with changes in the assessment of activities of daily living, especially in the less-affected hand.

INTERPRETATION

HABIT-ILE decreased the intensity of mirror movements in a group of children with CP. Furthermore, mirror movement changes were associated with bimanual performance and activities of daily living in these children.

WHAT THIS PAPER ADDS

The intensity of mirror movements decreased in both hands after 2 weeks of Hand and Arm Bimanual Intensive Therapy Including Lower Extremity (HABIT-ILE) training. Mirror movement changes were maintained at the 3-month follow-up after HABIT-ILE. Mirror movement changes were associated with improvements in bimanual performance and activities of daily living.

Influence of the Somatic Rubber Hand Illusion on Maximum Grip Aperture

The classic rubber hand illusion (RHI), based on visual, proprioceptive, and tactile feedback, can affect actions. However, it is not known whether these effects still occur if the paradigm is administered without visual feedback. In this study, we used the somatic RHI to test in thirty-two healthy individuals whether the incorporation of the rubber hand based on proprioceptive and tactile information only is sufficient to generate changes in actions. We measured maximum grip aperture (GA) changes towards a target and associated brain activations within the dorsal stream before and after the somatic RHI. Behavioural and neuroimaging data do not support an effect on maximum GA when the RHI is based on proprioceptive and tactile information only.

The Effect of Repetitive Transcranial Magnetic Stimulation of Cerebellar Swallowing Cortex on Brain Neural Activities: A Resting-State fMRI Study

Objective

The effects and possible mechanisms of cerebellar high-frequency repetitive transcranial magnetic stimulation (rTMS) on swallowing-related neural networks were studied using resting-state functional magnetic resonance imaging (rs-fMRI).

Method

A total of 23 healthy volunteers were recruited, and 19 healthy volunteers were finally included for the statistical analysis. Before stimulation, the cerebellar hemisphere dominant for swallowing was determined by the single-pulse TMS. The cerebellar representation of the suprahyoid muscles of this hemisphere was selected as the target for stimulation with 10 Hz rTMS, 100% resting motor threshold (rMT), and 250 pulses, with every 1 s of stimulation followed by an interval of 9 s. The motor evoked potential (MEP) amplitude of the suprahyoid muscles in the bilateral cerebral cortex was measured before and after stimulation to evaluate the cortical excitability. Forty-eight hours after elution, rTMS was reapplied on the dominant cerebellar representation of the suprahyoid muscles with the same stimulation parameters. Rs-fMRI was performed before and after stimulation to observe the changes in amplitude of low-frequency fluctuation (ALFF) and regional homology (ReHo) at 0.01–0.08 Hz, 0.01–0.027 Hz, and 0.027–0.073 Hz.

Results

After cerebellar high-frequency rTMS, MEP recorded from swallowing-related bilateral cerebral cortex was increased. The results of rs-fMRI showed that at 0.01–0.08 Hz, ALFF was increased at the pons, right cerebellum, and medulla and decreased at the left temporal lobe, and ReHo was decreased at the left insular lobe, right temporal lobe, and corpus callosum. At 0.01–0.027 Hz, ALFF was decreased at the left temporal lobe, and ReHo was decreased at the right temporal lobe, left putamen, and left supplementary motor area.

Conclusion

Repetitive transcranial magnetic stimulation of the swallowing cortex in the dominant cerebellar hemisphere increased the bilateral cerebral swallowing cortex excitability and enhanced pontine, bulbar, and cerebellar spontaneous neural activity, suggesting that unilateral high-frequency stimulation of the cerebellum can excite both brainstem and cortical swallowing centers. These findings all provide favorable support for the application of cerebellar rTMS in the clinical practice.

Regional Gray Matter Volume Changes in Brains of Patients With Ulcerative Colitis

BACKGROUND

Ulcerative colitis (UC) and Crohn's disease (CD) are 2 subtypes of inflammatory bowel disease (IBD). Several studies have reported brain abnormalities in IBD patients. This study aims to identify differences of gray matter volume (GMV) between patients with UC and healthy controls (HCs).

METHODS

Fifty-seven patients with UC and 40 HCs underwent structural magnetic resonance imaging. Voxel-based morphometry method was used to detect GMV differences. Receiver operating characteristic (ROC) curve was applied to investigate reliable biomarkers for identifying patients with UC from HCs. Regression analysis was used to examine relationships between the structure alternations and clinical symptoms.

RESULTS

Compared with HCs, patients with UC showed decreased GMV in the insula, thalamus, pregenual anterior cingulate cortex, hippocampus/parahippocampus, amygdala, and temporal pole; they showed increased GMV in the putamen, supplementary motor area, periaqueductal gray, hypothalamus, and precentral gyrus. Receiver operating characteristic analysis showed the highest classification power of thalamus. The inclusion of anxiety and depression as covariates eliminated the differences in the right insula, pregenual anterior cingulate cortex, supplementary motor area, and precentral gyrus. Most of the GMV changes were found in active patients with UC, with few changes in patients with UC in remission. We also found significantly negative correlation between UC duration and GMV in several regions.

CONCLUSION

The current neuroimaging findings were involved in visceral sensory pathways and were partially associated with the levels of anxiety and depression and clinical stage of patients with UC. This study might provide evidence for possible neuromechanisms of UC.

Characterizing Sensorimotor-Related Area Abnormalities in Amyotrophic Lateral Sclerosis: An Intravoxel Incoherent Motion Magnetic Resonance Imaging Study

RATIONALE AND OBJECTIVES

To investigate the microperfusion and water molecule diffusion alterations in sensorimotor-related areas in amyotrophic lateral sclerosis (ALS) using intravoxel incoherent motion (IVIM) magnetic resonance imaging.

MATERIALS AND METHODS

IVIM data were obtained from 43 ALS patients and 31 controls. This study employed the revised ALS Functional Rating Scale (ALSFRS-R) in evaluating disease severity. IVIM-derived metrics were calculated, including diffusion coefficient (D), pseudo-diffusion coefficient, and perfusion fraction. Conventional apparent diffusion coefficient was also computed. Atlas-based analysis was conducted to detect between-group difference in these metrics in sensorimotor-related gray/white matter areas. Spearman correlation analysis was employed to establish correlation between various metrics and ALSFRS-R.

RESULTS

ALS patients had perfusion fraction (× 10^-3) reduction in the left presupplementary motor area (60.72 ± 16.15 vs. 71.15 ± 12.98, p = 0.016), right presupplementary motor area (61.35 ± 17.02 vs. 72.18 ± 14.22, p = 0.016), left supplementary motor area (55.73 ± 12.29 vs. 64.12 ± 9.17, p = 0.015), and right supplementary motor area (56.53 ± 11.93 vs. 63.67 ± 10.03, p = 0.020). Patients showed D (× 10^-6 mm²/s) increase in a white matter tract projecting to the right ventral premotor cortex (714.20 ± 39.75 vs. 691.01 ± 24.53, p = 0.034). A negative correlation between D of right ventral premotor cortex tract and ALSFRS-R score was observed (r = -0.316, p = 0.039).

CONCLUSION

These findings suggest aberrant microperfusion and water molecule diffusion in the sensorimotor-related areas in ALS patients, which are associated with motor impairment in ALS.

Non-linear Functional Brain Co-activations in Short-Term Memory Distortion Tasks

Recent works shed light on the neural correlates of true and false recognition and the influence of time of day on cognitive performance. The current study aimed to investigate the modulation of the false memory formation by the time of day using a non-linear correlation analysis originally designed for fMRI resting-state data. Fifty-four young and healthy participants (32 females, mean age: 24.17 ± 3.56 y.o.) performed in MR scanner the modified Deese-Roediger-McDermott paradigm in short-term memory during one session in the morning and another in the evening. Subjects’ responses were modeled with a general linear model, which includes as a predictor the non-linear correlations of regional BOLD activity with the stimuli, separately for encoding and retrieval phases. The results show the dependence of the non-linear correlations measures with the time of day and the type of the probe. In addition, the results indicate differences in the correlations measures with hippocampal regions between positive and lure probes. Besides confirming previous results on the influence of time-of-day on cognitive performance, the study demonstrates the effectiveness of the non-linear correlation analysis method for the characterization of fMRI task paradigms.

Altered Local Brain Amplitude of Fluctuations in Patients With Myotonic Dystrophy Type 1

This study is aimed at investigating the characteristics of the spontaneous brain activity in patients with myotonic dystrophy type 1 (DM1). A total of 18 patients with DM1 and 18 healthy controls (HCs) were examined by resting-state functional MRI. Combined methods include amplitude of low-frequency fluctuations (ALFFs), the fractional amplitude of low-frequency fluctuations (fALFFs), and Wavelet transform-based ALFFs (Wavelet-ALFFs) with standardization, percent amplitude of fluctuation (PerAF) with/without standardization were applied to evaluate the spontaneous brain activity of patients with DM1. Compared with HCs, patients with DM1 showed decreased ALFFs and Wavelet-ALFFs in the bilateral precuneus (PCUN), angular gyrus (ANG), inferior parietal, but supramarginal and angular gyri (IPL), posterior cingulate gyrus (PCG), superior frontal gyrus, medial (SFGmed), middle occipital gyrus (MOG), which were mainly distributed in the brain regions of default mode network (DMN). Decreased ALFFs and Wavelet-ALFFs were also seen in bilateral middle frontal gyrus (MFG), inferior frontal gyrus, opercular part (IFGoperc), which were the main components of the executive control network (ECN). Patients with DM1 also showed decreased fALFFs in SFGmed.R, the right anterior cingulate and paracingulate gyri (ACGR), bilateral MFG. Reduced PerAF in bilateral PCUN, ANG, PCG, MOG, and IPLL as well as decreased PerAF without standardization in PCUNR and bilateral PCG also existed in patients with DM1. In conclusion, patients with DM1 had decreased activity in DMN and ECN with increased fluctuations in the temporal cortex and cerebellum. Decreased brain activity in DMN was the most repeatable and reliable with PCUN and PCG being the most specific imaging biomarker of brain dysfunction in patients with DM1.

MRI of Transcallosal White Matter Helps to Predict Motor Impairment in Multiple Sclerosis

Background Altered callosal integrity has been associated with motor deficits in patients with multiple sclerosis (MS), but its contribution to disability has, to the knowledge of the authors, not been investigated by using multiparametric MRI approaches. Purpose To investigate structural and functional interhemispheric MRI substrates of global disability at different milestones and upper limb motor impairment in MS. Materials and Methods In this cross-sectional study, healthy control patients and patients with MS (between January 1, 2008, and December 31, 2016) were retrospectively selected from our hospital database. Clinical assessment included Expanded Disability Status Scale (EDSS), nine-hole peg test, and digital finger tapping test. By using structural and resting-state functional MRI sequences, probabilistic tractography of hand corticospinal tract fibers, and transcallosal fibers between hand-motor cortices (hereafter, referred to as hand-M1), supplementary motor areas (SMAs), premotor cortices (PMCs), and voxel-mirror homotopic connectivity (VMHC) were analyzed. Random forest analyses identified the MRI predictors of clinical disability at different milestones (EDSS scores of 3.0, 4.0, 6.0) and upper limb motor impairment (nine-hole peg test and finger tapping test z scores < healthy control patients 5th percentile). Results One-hundred thirty healthy control patients (median age, 39 years; interquartile range, 31-50 years; 70 women) and 340 patients with MS (median age, 43 years; interquartile range, 33-51 years; 213 women) were studied. EDSS 3.0 predictors (n = 159) were global measures of atrophy and lesions together with damage measures of corticospinal tracts and transcallosal fibers between PMCs and SMAs (accuracy, 86%; P = .001-.01). For EDSS 4.0 (n = 131), similar predictors were found in addition to damage in transcallosal fibers between hand-M1 (accuracy, 89%; P = .001-.049). No MRI predictors were found for EDSS 6.0 (n = 70). Nine-hole peg test (right, n = 161; left, n = 166) and finger tapping test (right, n = 117; left, n = 111) impairments were predicted by damage in transcallosal fibers between SMAs and PMCs (accuracy range, 69%-77%; P = .001-.049). VMHC abnormalities did not explain clinical outcomes. Conclusion Structural, not functional, abnormalities at MRI in transcallosal premotor and motor white matter fibers predicted severity of global disability and upper limb motor impairment in patients with multiple sclerosis. The informative role of such predictors appeared less evident at higher disability levels. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Barkhof and Pontillo in this issue.

Identification of a Brain Network Underlying the Execution of Freely Chosen Movements

Action selection refers to the decision regarding which action to perform in order to reach a desired goal, that is, the "what" component of intention. Whether the action is freely chosen or externally instructed involves different brain networks during the selection phase, but it is assumed that the way an action is selected should not influence the subsequent execution phase of the same movement. Here, we aim to test this hypothesis by investigating whether the modality of movement selection influences the brain networks involved during the execution phase of the movement. Twenty healthy volunteers performed a delayed response task in an event-related functional magnetic resonance imaging design to compare freely chosen and instructed unimanual or bimanual movements during the execution phase. Using activation analyses, we found that the pre-supplementary motor area (preSMA) and the parietal and cerebellar areas were more activated during the execution phase of freely chosen as compared to instructed movements. Connectivity analysis showed an increase of information flow between the right posterior parietal cortex and the cerebellum for freely chosen compared to instructed movements. We suggest that the parieto-cerebellar network is particularly engaged during freely chosen movement to monitor the congruence between the intentional content of our actions and their outcome.

Neural mechanisms mediating cross education: With additional considerations for the ageing brain

CALVERT, G.H.M., and CARSON, R.G. Neural mechanisms mediating cross education: With additional considerations for the ageing brain. NEUROSCI BIOBEHAV REV 21(1) XXX-XXX, 2021. - Cross education (CE) is the process whereby a regimen of unilateral limb training engenders bilateral improvements in motor function. The contralateral gains thus derived may impart therapeutic benefits for patients with unilateral deficits arising from orthopaedic injury or stroke. Despite this prospective therapeutic utility, there is little consensus concerning its mechanistic basis. The precise means through which the neuroanatomical structures and cellular processes that mediate CE may be influenced by age-related neurodegeneration are also almost entirely unknown. Notwithstanding the increased incidence of unilateral impairment in later life, age-related variations in the expression of CE have been examined only infrequently. In this narrative review, we consider several mechanisms which may mediate the expression of CE with specific reference to the ageing CNS. We focus on the adaptive potential of cellular processes that are subserved by a specific set of neuroanatomical pathways including: the corticospinal tract, corticoreticulospinal projections, transcallosal fibres, and thalamocortical radiations. This analysis may inform the development of interventions that exploit the therapeutic utility of CE training in older persons.

Amble Gait EEG Points at Complementary Cortical Networks Underlying Stereotypic Multi-Limb Co-ordination

Background

Walking is characterized by stable antiphase relations between upper and lower limb movements. Such bilateral rhythmic movement patterns are neuronally generated at levels of the spinal cord and brain stem, that are strongly interconnected with cortical circuitries, including the Supplementary Motor Area (SMA).

Objective

To explore cerebral activity associated with multi-limb phase relations in human gait by manipulating mutual attunement of the upper and lower limb antiphase patterns.

Methods

Cortical activity and gait were assessed by ambulant EEG, accelerometers and videorecordings in 35 healthy participants walking normally and 19 healthy participants walking in amble gait, where upper limbs moved in-phase with the lower limbs. Power changes across the EEG frequency spectrum were assessed by Event Related Spectral Perturbation analysis and gait analysis was performed.

Results

Amble gait was associated with enhanced Event Related Desynchronization (ERD) prior to and during especially the left swing phase and reduced Event Related Synchronization (ERS) at final swing phases. ERD enhancement was most pronounced over the putative right premotor, right primary motor and right parietal cortex, indicating involvement of higher-order organization and somatosensory guidance in the production of this more complex gait pattern, with an apparent right hemisphere dominance. The diminished within-step ERD/ERS pattern in amble gait, also over the SMA, suggests that this gait pattern is more stride driven instead of step driven.

Conclusion

Increased four-limb phase complexity recruits distributed networks upstream of the primary motor cortex, primarily lateralized in the right hemisphere. Similar parietal-premotor involvement has been described to compensate impaired SMA function in Parkinson’s disease bimanual antiphase movement, indicating a role as cortical support regions.

Congenital Mirror Movements Associated With Brain Malformations

BACKGROUND

Congenital mirror movements are involuntary movements of a side of the body imitating intentional movements on the opposite side, appearing in early childhood and persisting beyond 7 years of age. Congenital mirror movements are usually idiopathic but have been reported in association with various brain malformations.

METHODS

We describe clinical, genetic, and radiologic features in 9 individuals from 5 families manifesting congenital mirror movements.

RESULTS

The brain malformations associated with congenital mirror movements were: dysplastic corpus callosum in father and daughter with a heterozygous p.Met1* mutation in DCC; hypoplastic corpus callosum, dysgyria, and malformed vermis in a mother and son with a heterozygous p.Thr312Met mutation in TUBB3; dysplastic corpus callosum, dysgyria, abnormal vermis, and asymmetric ventricles in a father and 2 daughters with a heterozygous p.Arg121Trp mutation in TUBB; hypoplastic corpus callosum, dysgyria, malformed basal ganglia and abnormal vermis in a patient with a heterozygous p.Glu155Asp mutation in TUBA1A; hydrocephalus, hypoplastic corpus callosum, polymicrogyria, and cerebellar cysts in a patient with a homozygous p.Pro312Leu mutation in POMGNT1.

CONCLUSION

DCC, TUBB3, TUBB, TUBA1A, POMGNT1 cause abnormal axonal guidance via different mechanisms and result in congenital mirror movements associated with brain malformations.

Loss of floor plate Netrin-1 impairs midline crossing of corticospinal axons and leads to mirror movements

In humans, execution of unimanual movements requires lateralized activation of the primary motor cortex, which then transmits the motor command to the contralateral hand through the crossed corticospinal tract (CST). Mutations in NTN1 alter motor control lateralization, leading to congenital mirror movements. To address the role of midline Netrin-1 on CST development and subsequent motor control, we analyze the morphological and functional consequences of floor plate Netrin-1 depletion in conditional knockout mice. We show that depletion of floor plate Netrin-1 in the brainstem critically disrupts CST midline crossing, whereas the other commissural systems are preserved. The only associated defect is an abnormal entry of CST axons within the inferior olive. Alteration of CST midline crossing results in functional ipsilateral projections and is associated with abnormal symmetric movements. Our study reveals the role of Netrin-1 in CST development and describes a mouse model recapitulating the characteristics of human congenital mirror movements.

Scalp Acupuncture Enhances the Functional Connectivity of Visual and Cognitive-Motor Function Network of Patients with Acute Ischemic Stroke

Design

A parallel-group randomized controlled trial. Participants. 30 hemiplegic patients with middle cerebral artery acute infarction of the dominant hemisphere. Interventions. 30 patients were divided into 2 groups randomly. 15 patients in the treatment group (TG) were treated with ISSA, needling at the parietal midline (MS5) and left anterior/posterior parietal-temporal oblique lines (MS6 and MS7), combined with western routine treatment. While another 15 patients in the control group (CG) received routine treatment only. Main Outcome Measures. (1) Functional connectivity (FC): patients received brain scan using 3.0 T MRI after the treatment for 1 week. Based on the Matlab2012a platform, SPM12 software and DPABI software were used to process the scanning data and finally the functional connectivity of the brain was obtained. (2) National Institute of Health Stroke Scale (NIHSS) score.

Results

The difference in the NIHSS score between the two groups of patients before and after treatment was statistically significant (tNIHSS = 2.225; PNIHSS = 0.038), indicating that TG had a better effect. Centered to the seed region of the left supplementary motor area (SMA) (-5.32, 4.85, 61.38), FC increased at the left middle cerebellar peduncle, left cerebellum posterior lobe (uvula and declive), vermis, fusiform gyrus, lingual gyrus, inferior occipital gyrus, calcarine, cuneus, precuneus, BA7, BA18 and BA19, etc. Centered to the seed region of the left parahippocampal gyrus (PG) (-21.17, -15.95, -20.70), FC increased at the left precuneus, inside-paracingulate, inferior parietal gyrus, paracentral lobule, BA5, BA6, BA7, and BA40, right median cingulate, precuneus, BA19, BA23, and BA31, etc.

Conclusions

It is indicated that ISSA can regulate the brain functional connection in patients with middle cerebral artery acute infarction in the dominant hemisphere and specifically strengthen the connections between visual, cognitive, motor control, and planning-related brain regions, which may be related to the recovery of movement in the mechanism. This trial is registered with ChiCTR-IOR-15007672.

Corticospinal Fibers With Different Origins Impact Motor Outcome and Brain After Subcortical Stroke

BACKGROUND AND PURPOSE

Motor deficit is the most common disability after stroke, and early prediction of motor outcome is critical for early interventions. Here, we constructed a fine map of the corticospinal tract (CST) for early prediction of motor outcome and for understanding the secondary brain changes after subcortical stroke.

METHODS

Diffusion spectrum imaging data from 50 healthy adults were used to reconstruct fine maps of CST with different origins, including primary motor area (M1), primary sensory area (S1), premotor cortex, and supplementary motor area (SMA). Their diffusion properties correlated with motor functions in healthy adults. The impacts of the impairments of different CST on motor outcomes and on structural and functional changes of brain were investigated in 136 patients with subcortical stroke by combining CST damage-symptom association study and voxel-based lesion-symptom mapping.

RESULTS

In healthy adults, the isotropy of M1 fiber correlated with walking endurance and that of SMA fiber with motor dexterity. In chronic stroke patients, the integrity of M1 and SMA fibers showed the most significant correlation with motor deficits. The percentage of early damage of M1 and SMA fibers correlated with that of chronic motor deficits. Voxel-based lesion-symptom mapping revealed that acute stroke lesions in the bilateral M1 and right SMA fibers were associated with chronic motor deficits. The early damage of M1 fiber negatively correlated with the integrity of M1-M1 fiber, and the early damage of SMA fiber negatively correlated with gray matter volume of the contralateral cerebellum in the chronic stage.

CONCLUSIONS

The CST that originated from the M1 and SMA are closely associated with motor outcomes and brain structural changes, and the fine maps of CST from these 2 cortical areas are useful in assessing and predicting long-term motor outcome in patients with subcortical stroke.

Evidence for asymmetric inhibitory activity during motor planning phases of sensorimotor synchronization

Sensorimotor synchronization (SMS) is frequently dependent on coordination of excitatory and inhibitory activity across hemispheres, as well as the cognitive control over environmental distractors. However, the timing (motor planning versus execution) and cortical regions involved in these processes remain actively debated. Functional magnetic resonance imaging data were therefore analyzed from 34 strongly right-handed healthy adults performing a cued (to initiate motor planning) SMS task with either their right or left hand (motor execution phase) based on spatially congruent or incongruent visual stimuli. Behavioral effects of incongruent stimuli were limited to the first stimulus. Functionally, greater activation was observed in left sensorimotor cortex (SMC) and right cerebellar Lobule V for congruent versus incongruent stimuli. A negative blood-oxygen level dependent response, a putative marker of neural inhibition, was present in bilateral SMC, right supplemental motor area (SMA) and bilateral cerebellar Lobule V during the motor planning, but not execution phase. The magnitude of the inhibitory response was greater in right cortical regions and cerebellar Lobule V. Homologue connectivity was associated with inhibitory activity in the right SMA, suggesting that individual differences in intrinsic connectivity may mediate transcallosal inhibition. In summary, results suggest increased inhibition (i.e., greater negative BOLD response) within the right relative to left hemisphere, which was released once motor programs were executed. Both task and intrinsic functional connectivity results highlight a critical role of the left SMA in interhemispheric inhibition and motor planning.

Altered Resting-State Functional Connectivity of Multiple Networks and Disrupted Correlation With Executive Function in Major Depressive Disorder

Background: Major depressive disorder (MDD) is one of the most common and costly psychiatric disorders. In addition to significant changes in mood, MDD patients face an increased risk of developing cognitive dysfunction. It is important to gain an improved understanding of cognitive impairments and find a biomarker for cognitive impairment diagnosis in MDD.

Methods: One hundred MDD patients and 100 normal controls (NCs) completed resting-state fMRI (rs-fMRI) scan, in which 34 MDD patients and 34 NCs had scores in multiple cognitive domains (executive function, verbal fluency, and processing speed). Twenty-seven regions of interest from the default mode network (DMN), central executive network (CEN), salience network (SN), and limbic system (LS) were selected as seeds for functional connectivity (FC) analyses with the voxels in the whole brain. Finally, partial correlations were conducted for cognitive domain scores and FCs with significant differences between the MDD and NC groups.

Results: Significant FC differences between groups were identified among the seeds and clusters in the DMN, CEN, LS, visual network, somatomotor network, ventral attention network, and dorsal attention network. In the MDD patients, the magnitude of the Stroop interference effect was positively correlated with the illness duration, and the illness duration was negatively correlated with the FC between the right ventral hippocampal gyrus and the left inferior frontal gyrus. However, the correlation between the Stroop interference effect and the FC of the right anterior prefrontal cortex with the left cerebellum_4_5 was disrupted in these patients.

Conclusions: The MDD patients have altered FCs among multiple brain networks and a disrupted correlation between the FC of prefrontal cortex and executive function. The disrupted correlation could present before the symptoms develop and may be the core process in the development of executive function impairment.

Cortical Functional Domains Show Distinctive Oscillatory Dynamic in Bimanual and Mirror Visual Feedback Tasks

It is believed that Mirror Visual Feedback (MVF) increases the interlimb transfer but the exact mechanism is still a matter of debate. The aim of this study was to compare between a bimanual task (BM) and a MVF task, within functionally rather than geometrically defined cortical domains. Measure Projection Analysis (MPA) approach was applied to compare the dynamic oscillatory activity (event-related synchronization/desynchronization ERS/ERD) between and within domains. EEG was recorded in 14 healthy participants performing a BM and an MVF task with the right hand. The MPA was applied on fitted equivalent current dipoles based on independent components to define domains containing functionally similar areas. The measure of intradomain similarity was a "signed mutual information," a parameter based on the coherence. Domain analysis was performed for joint tasks (BM and MVF) and for each task separately. MVF created 9 functional domains while MB task had only 4 functionally distinctive domains, two over the left hemispheres and two bilateraly. For all domains identified for BM task alone, similar domains could be identified in MVF and joint tasks analysis. In addition MVF had domains related to motor planning on the right hemisphere and to self-recognition of action. For joint tasks analysis, seven domains were identified, with similar functions for the left and the right hand with exception of a domain covering BA32 (self-recognition of action) of the left hand only. In joint task domain analysis, the ERD/ERS showed a larger difference between domains than between tasks. All domains which involved the sensory cortex had a visible beta ERS at the onset of movement, and post movement beta ERS. The frequency of ERD varied between domains. Largest difference between tasks existed in domains responsible for the awareness of action. In conclusion, functionally distinctive domains have different ERD/ERS patterns, similar for both tasks. MVF activates contralateral hemisphere in similar manner to BM movements, while at the same time also activating the ipsilateral hemisphere. Significance: Following stroke cortical activation and interhemispheric inhibition from the contralesional side is reduced. MVF creates stronger ipsilateral activity than BM, which is highly relevant of neurorehabilitation of movements.

The supplementary motor area modulates interhemispheric interactions during movement preparation

The execution of coordinated hand movements requires complex interactions between premotor and primary motor areas in the two hemispheres. The supplementary motor area (SMA) is involved in movement preparation and bimanual coordination. How the SMA controls bimanual coordination remains unclear, although there is evidence suggesting that the SMA could modulate interhemispheric interactions. With a delayed-response task, we investigated interhemispheric interactions underlying normal movement preparation and the role of the SMA in these interactions during the delay period of unimanual or bimanual hand movements. We used functional MRI and transcranial magnetic stimulation in 22 healthy volunteers (HVs), and then in two models of SMA dysfunction: (a) in the same group of HVs after transient disruption of the right SMA proper by continuous transcranial magnetic theta-burst stimulation; (b) in a group of 22 patients with congenital mirror movements (CMM), whose inability to produce asymmetric hand movements is associated with SMA dysfunction. In HVs, interhemispheric connectivity during the delay period was modulated according to whether or not hand coordination was required for the forthcoming movement. In HVs following SMA disruption and in CMM patients, interhemispheric connectivity was modified during the delay period and the interhemispheric inhibition was decreased. Using two models of SMA dysfunction, we showed that the SMA modulates interhemispheric interactions during movement preparation. This unveils a new role for the SMA and highlights its importance in coordinated movement preparation.