Ipsilateral Motor Areas Research Articles

Parieto-motor functional connectivity is impaired in Parkinson's disease

BackgroundBradykinesia in Parkinson's disease is associated with a difficulty in selecting and executing motor actions, likely due to alterations in the functional connectivity of cortico-cortical circuits. Objective/HypothesisOur aims were to analyse the functional interplay between the posterior parietal cortex and the ipsilateral primary motor area in Parkinson's disease using bifocal transcranial magnetic stimulation, to evaluate its modulation by dopaminergic treatment and its relationship to a simple choice reaction task. MethodsWe studied 12 Parkinson's disease patients with and without dopaminergic treatment and 12 healthy controls. A paired-pulse transcranial magnetic stimulation protocol was applied over the right posterior parietal cortex and the right primary motor area using different conditioning stimulus intensities and interstimulus intervals. Reaction and movement times were studied by a simple choice reaction task. ResultsIn controls, we observed a significant facilitation of motor evoked potential amplitudes at 4 ms interstimulus interval when conditioning stimulus intensity was set to 90% of resting motor threshold. This functional interaction was not observed in Parkinson's disease patients without dopaminergic treatment and was not restored with treatment. Moreover, correlation analyses revealed that Parkinson's disease patients with less impaired parieto-motor interaction were faster in executing reaching movements in a choice reaction time task, suggesting that the functional parieto-motor impairment described here could be related to bradykinesia observed in Parkinson's disease patients. ConclusionsParieto-motor functional connectivity is impaired in Parkinson's disease. The reduced efficacy of this connection could be related to presence of bradykinesia previously observed in Parkinson's disease.

Age-related changes in causal interactions between cortical motor regions during hand grip

Brain activity during motor performance becomes more widespread and less lateralized with advancing age in response to ongoing degenerative processes. In this study, we were interested in the mechanism by which this change in the pattern of activity supports motor performance with advancing age. We used both transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) to assess age related changes in motor system connectivity during isometric hand grip. Paired pulse TMS was used to measure the change in interhemispheric inhibition (IHI) from contralateral M1 (cM1) to ipsilateral M1 (iM1) during right hand grip. Dynamic Causal Modelling (DCM) of fMRI data was used to investigate the effect of age on causal interactions throughout the cortical motor network during right hand grip. Bayesian model selection was used to identify the causal model that best explained the data for all subjects. Firstly, we confirmed that the TMS and DCM measures both demonstrated a less inhibitory/more facilitatory influence of cM1 on iM1 during hand grip with advancing age. These values correlated with one another providing face validity for our DCM measures of connectivity. We found increasing reciprocal facilitatory influences with advancing age (i) between all ipsilateral cortical motor areas and (ii) between cortical motor areas of both hemispheres and iM1. There were no differences in the performance of our task with ageing suggesting that the ipsilateral cortical motor areas, in particular iM1, play a central role in maintaining performance levels with ageing through increasingly facilitatory cortico-cortical influences.

Impaired cortical deactivation during hand movement in the relapsing phase of multiple sclerosis: a cross-sectional and longitudinal fMRI study

Background: Little is known about the cortical activation changes during clinical relapses in multiple sclerosis (MS). Objective: To assess cross-sectional and longitudinal differences in functional magnetic resonance imaging (fMRI) cortical patterns between the relapsing and stable phases of MS. Methods: We studied 32 patients with relapsing–remitting MS with mild disability: 19 within 48 h of symptom onset of a new relapse (G1) and 13 in the stable phase, relapse-free for at least 6 months (G2). All patients underwent fMRI twice, upon entry (time 1) and 30–50 days later (time 2), during right-hand movement. Results: No between-group differences were observed in age, disability or T2 lesion load. Between-group analysis showed a significant difference in the ipsilateral precentral gyrus (IPG) activation at time 1. Activity differences in the IPG expressed reduced deactivation in G1 compared with G2. Longitudinal changes in brain activity in the IPG were significantly greater in G1 than G2. G1 patients with a slow clinical recovery (n = 8) showed different activity at baseline and greater activity changes over time in the IPG than patients with a fast recovery (n = 11). Conclusion: This study shows that the relapsing phase is associated with reduced brain deactivation in the IPG, which is more marked in patients with a slow clinical recovery. Increased cortical excitability associated with inflammation may determine functional modifications within the ipsilateral motor area.

Arterial spin labeling for motor activation mapping at 3T with a 32-channel coil: Reproducibility and spatial accuracy in comparison with BOLD fMRI

Functional arterial spin labeling (fASL) is an innovative biomarker of neuronal activation that allows direct and absolute quantification of activation-related CBF and is less sensitive to venous contamination than BOLD fMRI. This study evaluated fASL for motor activation mapping in comparison with BOLD fMRI in terms of involved anatomical area localization, intra-individual reproducibility of location, quantification of neuronal activation, and spatial accuracy. Imaging was performed at 3T with a 32-channel coil and dedicated post-processing tools were used. Twelve healthy right-handed subjects underwent fASL and BOLD fMRI while performing a right hand motor activation task. Three sessions were performed 7days apart in similar physiological conditions. Our results showed an activation in the left primary hand motor area for all 36 sessions in both fASL and BOLD fMRI. The individual functional maps for fASL demonstrated activation in ipsilateral secondary motor areas more often than the BOLD fMRI maps. This finding was corroborated by the group maps. In terms of activation location, fASL reproducibility was comparable to BOLD fMRI, with a distance between activated volumes of 2.1mm and an overlap ratio for activated volumes of 0.76, over the 3 sessions. In terms of activation quantification, fASL reproducibility was higher, although not significantly, with a CVintra of 11.6% and an ICC value of 0.75. Functional ASL detected smaller activation volumes than BOLD fMRI but the areas had a high degree of co-localization. In terms of spatial accuracy in detecting activation in the hand motor area, fASL had a higher specificity (43.5%) and a higher positive predictive value (69.8%) than BOLD fMRI while maintaining high sensitivity (90.7%). The high intra-individual reproducibility and spatial accuracy of fASL revealed in the present study will subsequently be applied to pathological subjects.

Functional role of ipsilateral motor areas in multiple sclerosis

BackgroundIn patients with multiple sclerosis (MS), motor tasks are associated with increased activation of ipsilateral motor cortical areas. The authors examined the role of two ipsilateral motor areas during performance...

Brain oscillatory activity during motor imagery in EEG-fMRI coregistration

The purpose of the present work was to investigate the correlation between topographical changes in brain oscillatory activity and the blood oxygenation level-dependent (BOLD) signal during a motor imagery (MI) task using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) coregistration. EEG was recorded in 7 healthy subjects inside a 1.5 T MR scanner during the imagination of the kinesthetic experience of movement. A Fast Fourier Transform was applied to EEG signal in the rest and active conditions. We used the event-related-synchronization (ERS)/desynchronization (ERD) approach to characterize where the imagination of movement produces a decrease in alpha and beta power. The mean alpha map showed ERD decrease localized over the contralateral sensory motor area (SM1c) and a light desynchronization in the ipsilateral sensory motor area (SM1i); whereas the mean beta map showed ERD decrease over the supplementary motor area (SMA). fMRI showed significant activation in SMA, SM1c, SM1i. The correlation is negative in the contralateral side and positive in the ipsilateral side. Using combined EEG-fMRI signals we obtained useful new information on the description of the changes in oscillatory activity in alpha and beta bands during MI and on the investigation of the sites of BOLD activity as possible sources in generating these rhythms. By correlating BOLD and ERD/ERS we may identify more accurately which regions contribute to changes of the electrical response.

Cerebral activation is correlated to regional atrophy of the spinal cord and functional motor disability in spinal cord injured individuals

Recovery of function following lesions in the nervous system requires adaptive changes in surviving circuitries. Here we investigate whether changes in cerebral activation are correlated to spinal cord atrophy and recovery of functionality in individuals with incomplete spinal cord injury (SCI).19 chronic SCI individuals and 7 age-comparable controls underwent functional magnetic resonance imaging (fMRI) while performing rhythmic dorsiflexion of the ankle. A significant negative correlation was found between the activation in the ipsilateral motor (M1) and bilateral premotor cortex (PMC) on one hand and the functional ability of the SCI participants measured by the clinical motor score on the other. There was no significant correlation between activation in any other cerebral area and the motor score.Activation in ipsilateral somatosensory cortex (S1), M1 and PMC was negatively correlated to the width of the spinal cord in the left–right direction, where the corticospinal tract is located, but not in the antero-posterior direction. There was a tendency for a negative correlation between cerebral activation in ipsilateral S1, M1 and PMC and the amplitude of motor evoked potentials in the tibialis anterior muscle elicited by transcranial magnetic stimulation, but this did not reach statistical significance. There was no correlation between motor score or spinal cord dimensions and the volume of the cortical motor areas.The observations show that lesion of descending tracts in the lateral part of the spinal cord results in increased activation in ipsilateral motor and sensory areas, which may help to compensate for the functional deficit following SCI.

Fatiguing intermittent lower limb exercise influences corticospinal and corticocortical excitability in the nonexercised upper limb

It has recently been reported that unilateral fatiguing exercise affects not only the motor area innervating the exercising muscle but also the ipsilateral motor area innervating homologous nonexercised muscle. This study was designed to clarify the effects of fatiguing intermittent lower limb exercise on the excitability of the motor cortex representation of nonexercised muscles in the arm. Eight subjects performed an intermittent leg press exercise composed of three bouts of 5-minute leg press (T1, T2, and T3) at 50% of maximal voluntary contraction separated by a 2-minute rest. Motor-evoked potentials (MEP), short interval intracortical inhibition (SICI), and intracortical facilitation (ICF), using paired-pulse transcranial magnetic stimulation, were assessed in two nonexercised arm muscles (first dorsal interosseous muscle: FDI, n = 8; biceps brachii muscle: BB, n = 6) and one exercised leg muscle (quadriceps femoris muscle: QF, n = 6) before and immediately after each bout of exercise and for 30 minutes during recovery after the end of the third exercise bout (Experiment 1). Experiment 2 was the same as Experiment 1, except that the test pulse intensity was adjusted to produce a given amplitude of MEP(TEST) at each time point. MEPs and SICI in the exercised QF muscle were depressed at all time points during and after fatigue. In contrast, MEPs in nonexercised arm muscles were facilitated from T1-T3 (T3, only FDI), but were then depressed for up to 20 minutes in the recovery period. SICI was reduced in both muscles during T1-T3 and remained depressed until 20 minutes into recovery. ICF was unchanged in arm muscles but depressed in QF over T1-T3. The current study indicates that muscle fatigue induced by exercise of a large lower limb muscle group has powerful effects on the excitability of both SICI and the corticospinal projection to muscles of the nonexercised upper limb.

Changes in cerebral activity after decreased upper-limb hypertonus: an EMG-fMRI study

Whereas several studies have used functional magnetic resonance imaging (fMRI) to investigate motor recovery, whether therapy to decrease post-stroke hypertonus alters central motor patterns remains unclear. In this study, we used continuous electromyography (EMG)-fMRI to investigate possible changes in movement-related brain activation in patients receiving Botulinum toxin (BoNT-A) for hand-muscle hypertonus after chronic stroke. We studied eight stroke patients all of whom had hemiparesis and associated upper-limb hypertonus. All patients underwent an fMRI-EMG recording and clinical-neurological assessment before BoNT-A and 5 weeks thereafter. The handgrip motor task during imaging was fixed across both patients and controls. The movements were metronome paced, movement amplitude and force were controlled with a plastic orthosis, dynamometer and EMG recording. An age-matched control group was recruited from among healthy volunteers underwent the same fMRI-EMG recording. Before BoNT-A, while patients moved the paretic hand, fMRI detected wide bilateral activation in the sensorymotor areas (SM1), in the supplementary motor area (SMA) and cerebellum. After BoNT-A blood oxygenation level-dependent (BOLD) activation decreased in ipsilateral and contralateral motor areas and became more lateralized. BOLD activation decreased also in ipsilateral cerebellar regions and in the SMA. Changes in peripheral upper-limb hypertonus after BoNT-A were associated to an improvement in active movements and more lateralized and focalized activation of motor areas. The clinical and EMG-fMRI coregistration technique we used to study hand-muscle hypertonus in patients receiving BoNT-A after chronic stroke should be useful in future studies seeking improved strategies for post-stroke neurorehabilitation.

Graded cutaneous electrical vs thermal stimulation in humans shows different insular and cingulate cortex activation

Pain can result from various sensory input modalities. To elucidate the differences of cortical responses to graded electrical and thermal stimulation, functional magnetic resonance imaging (fMRI) results of two studies using the same stimulation paradigms but different modalities with 15 healthy subjects each are compared. During painful electrical stimulation contralateral dorsal posterior insula and ventral posterior anterior cingulate cortex (ACC) activated more. During thermal stimulation, there was more activation in ipsilateral primary motor area (MI)/primary sensory area (SI) complex and premotor areas as well as dorsal posterior ACC. Thus electrostimulation preferably activates structures of the lateral pain projection system resulting in contralateral dorsal posterior insula and ventral posterior ACC activation. During thermal stimulation, more dorsal areas of the posterior ACC activated. The activation of ipsilateral MI/SI complex and premotor areas may be attributed to the slower perception of thermal stimuli and resulting re-evaluation. This has to be taken into account in the interpretation of other cross-modality studies as well.

Loss of laterality in chronic cocaine users: An fMRI investigation of sensorimotor control

Movement disturbances are often overlooked consequences of chronic cocaine abuse. The purpose of this study was to systematically investigate sensorimotor performance in chronic cocaine users and characterize changes in brain activity among movement-related regions of interest (ROIs) in these users. Functional magnetic resonance imaging data were collected from 14 chronic cocaine users and 15 age- and gender-matched controls. All participants performed a sequential finger-tapping task with their dominant, right hand interleaved with blocks of rest. For each participant, percent signal change from rest was calculated for seven movement-related ROIs in both the left and right hemisphere. Cocaine users had significantly longer reaction times and higher error rates than controls. Whereas the controls used a left-sided network of motor-related brain areas to perform the task, cocaine users activated a less lateralized pattern of brain activity. Users had significantly more activity in the ipsilateral (right) motor and premotor cortical areas, anterior cingulate cortex and the putamen than controls. These data demonstrate that, in addition to the cognitive and affective consequences of chronic cocaine abuse, there are also pronounced alterations in sensorimotor control in these individuals, which are associated with functional alterations throughout movement-related neural networks.

The role of ipsilateral primary motor cortex in movement control and recovery from brain damage

The role of ipsilateral motor areas for movement control is not yet fully understood. The relevance of these areas to the recovery of motor function following a brain lesion is a matter of dispute. It has recently been stated that increased ipsilateral activation following brain damage is maladaptive and hindering the process of recovery. Others have presented evidence that ipsilateral motor areas subserve motor recovery. A recent study published in Experimental Neurology [Lotze, M., Sauseng, P., Staudt, M., 2009. Functional relevance of ipsilateral motor activation in congenital hemiparesis as tested by fMRI-navigated TMS. Exp. Neurol., 217, 440-443.] on patients with congenital hemiparesis presents evidence for the importance of ipsilateral primary motor cortex and dorsal premotor cortex to movement control even in the absence of direct ipsilateral descending output in this special set of patients. This comment briefly summarizes the relevant findings supporting both views and discusses potential causes for the prima facie contradictory findings.

Functional role of ipsilateral motor areas in a simple reaction task in multiple sclerosis

Background: Multiple sclerosis (MS) is a chronic neurological disease that is characterized by both demyelination and axonal injury within the central nervous system (CNS). Neuroplastic changes appear to play a role in functional compensation of brain lesions. These may involve reorganisation of cortical representations on a large anatomical scale. We studied the role of 2 ipsilateral motor areas on performance of a simple reaction time (SRT) task in patients with MS and matched controls using a virtual lesion approach. Moreover, we assessed the relationship between SRT changes following virtual lesion induction and motor impairment in MS patients.

High gamma mapping using EEG

High gamma (HG) power changes during motor activity, especially at frequencies above 70 Hz, play an important role in functional cortical mapping and as control signals for BCI (brain–computer interface) applications. Most studies of HG activity have used ECoG (electrocorticography) which provides high-quality spatially localized signals, but is an invasive method. Recent studies have shown that non-invasive modalities such as EEG and MEG can also detect task-related HG power changes. We show here that a 27 channel EEG (electroencephalography) montage provides high-quality spatially localized signals non-invasively for HG frequencies ranging from 83 to 101 Hz. We used a generic head model, a weighted minimum norm least squares (MNLS) inverse method, and a self-paced finger movement paradigm. The use of an inverse method enables us to map the EEG onto a generic cortex model. We find the HG activity during the task to be well localized in the contralateral motor area. We find HG power increases prior to finger movement, with average latencies of 462 ms and 82 ms before EMG (electromyogram) onset. We also find significant phase-locking between contra- and ipsilateral motor areas over a similar HG frequency range; here the synchronization onset precedes the EMG by 400 ms. We also compare our results to ECoG data from a similar paradigm and find EEG mapping and ECoG in good agreement. Our findings demonstrate that mapped EEG provides information on two important parameters for functional mapping and BCI which are usually only found in HG of ECoG signals: spatially localized power increases and bihemispheric phase-locking.

Alterations in voluntary movement execution in Huntington's disease are related to the dominant motor system — Evidence from event-related potentials

Huntington's disease is an autosomal dominant neurogenetic disorder leading to striatal atrophy, characterized by involuntary movements. Voluntary movements also deteriorate, but the neurophysiological mechanisms are less understood. We investigated voluntary movement execution and its neural correlates by means of movement-related potentials (MRPs) in symptomatic HD (HD), presymptomatic HD (pHD) and controls. Reaction times (RTs) revealed hand differences in controls and HD, but not in pHDs. Response-locked MRPs above the contralateral primary motor area (M1) were similar across all groups. Yet, the HD-group showed, selectively for the right hand, a second contralateral (left) activation after the response, followed by similar activation over the ipsilateral (right) motor area, which is normally inhibited. Similarly parietal processes were reversed for right hand movements. In strong contrast, pHDs showed an increased inhibition of the ipsilateral hemisphere. The results suggest modulations of inhibitory processes in HD dependent on disease stage. Importantly, these modulations occur after the response and are restricted to right-hand responses, or the dominant motor system (left hemisphere). Since also cognitive processes preceding the MRPs changed, the results suggest a cognitive contribution to the emergence of voluntary movement dysfunction. The pattern in the pHD-group, namely an increased inhibition of the ipsilateral hemisphere and similar RTs between the hands suggest compensatory mechanisms in presymptomatic stages of the disease. Despite neurophysiological alterations originating in the dominant left hemisphere in HDs, they also affect the right hemisphere, probably due to a dysfunction in interhemispheric inhibition in HD.

Dynamic intra- and interhemispheric interactions during unilateral and bilateral hand movements assessed with fMRI and DCM

Any motor action results from a dynamic interplay of various brain regions involved in different aspects of movement preparation and execution. Establishing a reliable model of how these areas interact is crucial for a better understanding of the mechanisms underlying motor function in both healthy subjects and patients. We used fMRI and dynamic causal modeling to reveal the specific excitatory and inhibitory influences within the human motor system for the generation of voluntary hand movements. We found an intrinsic balance of excitatory and inhibitory couplings among core motor regions within and across hemispheres. Neural coupling within this network was specifically modulated upon uni- and bimanual movements. During unimanual movements, connectivity towards the contralateral primary motor cortex was enhanced while neural coupling towards ipsilateral motor areas was reduced by both transcallosal inhibition and top-down modulation. Bimanual hand movements were associated with a symmetric facilitation of neural activity mediated by both increased intrahemispheric connectivity and enhanced transcallosal coupling of SMA and M1. The data suggest that especially the supplementary motor area represents a key structure promoting or suppressing activity in the cortical motor network driving uni- and bilateral hand movements. Our data demonstrate that fMRI in combination with DCM allows insights into intrinsic properties of the human motor system and task-dependent modulations thereof.

Stimulus context and motor preparation in attention-deficit/hyperactivity disorder

Aim To investigate (1) whether and how local stimulus context variation may modify behavioural and preparatory motor processes in children, and (2) if these effects differ between healthy children and children with attention-deficit/hyperactivity disorder (ADHD) aged 9–12 years. Methods Behavioural parameters and contingent negative variation (CNV) at cortical motor electrodes were recorded during a cued continuous performance task (AX-CPT) in three stimulus context conditions (Go, NoGo, neutral). Stimulus context was varied on the basis of stimulus types preceding the cue letter A. Results In all children, responses were slowed in both the NoGo- and Go-conditions relative to the neutral condition. Stimulus context affected preparatory motor processes in both groups but differentially. ADHD children showed smaller CNV potentials and a functionally irrelevant over-activation of the ipsilateral motor area. Conclusions Local stimulus context may modify behavioural and preparatory motor processes in children. In ADHD, local context variations may disrupt behaviour due to inefficient regulation of supervisory higher control systems.

Facial motor cortex plasticity in patients with unilateral peripheral facial paralysis

Hand motor representation area expands towards the area of the perioral facial motor cortex in patients with peripheral facial paralysis (PFP) and in hemifacial spasm cases treated with botulinum toxin. In this current study, we aimed to investigate the changes both in the ipsilateral and contralateral facial motor cortex areas in patients with PFP with transcranial magnetic stimulation (TMS). Thirty healthy individuals and 41 patients with unilateral PFP with partial or total axonal degeneration participated in this study. Motor evoked potentials (MEPs) of perioral muscles elicited by TMS of the intracranial portion of the facial nerve and motor cortex, were recorded. TMS was delivered through a figure-of-eight coil. Mapping of the cortical representation of perioral muscles were also studied in 13 of 41 patients and in 10 of control subjects. Mean amplitude of the intact perioral MEPs elicited by the ipsilateral hemisphere TMS, was significantly higher in patients than the control subjects. There was also a mild enlargement of the mean cortical representation area of intact perioral muscles on both hemispheres though it was not significant. We have concluded that there was a cortical reorganization in the hemisphere contralateral to the paralytic side resulting in an increase at corticofugal output related to intact perioral muscles.

Effect of corpus callosum damage on ipsilateral motor activation in patients with multiple sclerosis: A functional and anatomical study

Functional MRI (fMRI) studies have shown increased activation of ipsilateral motor areas during hand movement in patients with multiple sclerosis (MS). We hypothesized that these changes could be due to disruption of transcallosal inhibitory pathways. We studied 18 patients with relapsing-remitting MS. Conventional T1- and T2-weighted images were acquired and lesion load (LL) measured. Diffusion tensor imaging (DTI) was performed to estimate fractional anisotropy (FA) and mean diffusivity (MD) in the body of the corpus callosum (CC). fMRI was obtained during a right-hand motor task. Patients were studied to evaluate transcallosal inhibition (TCI, latency and duration) and central conduction time (CCT). Eighteen normal subjects were studied with the same techniques. Patients showed increased MD (P < 0.0005) and reduced FA (P < 0.0005) in the body of the CC. Mean latency and duration of TCI were altered in 12 patients and absent in the others. Between-group analysis showed greater activation in patients in bilateral premotor, primary motor (M1), and middle cingulate cortices and in the ipsilateral supplementary motor area, insula, and thalamus. A multivariate analysis between activation patterns, structural MRI, and neurophysiological findings demonstrated positive correlations between T1-LL, MD in the body of CC, and activation of the ipsilateral motor cortex (iM1) in patients. Duration of TCI was negatively correlated with activation in the iM1. Our data suggest that functional changes in iM1 in patients with MS during a motor task partially represents a consequence of loss of transcallosal inhibitory fibers.

A cluster-based quantitative procedure in an fMRI study of Parkinson's disease

Parkinson's disease is a neurological disorder associated with disfunction of dopaminergic pathways of the basal ganglia. In this study, we report the effects of decreasing plasma concentrations of the dopamine-agonist apomorphine on the size and extents of activity clusters observed with functional magnetic resonance imaging during a simple motor task. Eight patients at advanced disease stage and six healthy volunteers were studied during four consecutive sessions. We observed consistent activations in the primary sensorimotor area of the contralateral side and in the supplementary motor area of both patients and controls during the first session. During subsequent sessions, while the drug concentration gradually decreased in patients, they showed a fragmentation of the activity areas, with an overall decrease of involved volume and a decline of activity in the supplementary motor area. The appearing of activity in the ipsilateral motor area matched a partial recovery of supplementary motor area activation. During the last session, when patients showed severe dyskinesia, a widespread region of positive and negative correlations between signal and task was observed. We conclude that the lack of subcortical circuitry is partially reversible by apomorphine and that when the drug effects are reduced, there is a possible mechanism recruitment of alternate subcortical pathways.