Unilateral Motor Task Research Articles

Greater task difficulty during unilateral motor tasks changes intracortical inhibition and facilitation in the ipsilateral primary motor cortex in young men

This study aimed to clarify the changes in short-interval intracortical inhibition (SICI) and facilitation (ICF) in the ipsilateral primary motor cortex (iM1) when the task difficulty during unilateral force-matching tasks was manipulated. Twelve young male adults matched their left index finger abduction force to a displayed target force. Task difficulty was manipulated by varying the acceptable force range of the mean target force (5% MVC). Briefly, unilateral force-matching tasks with lesser and greater task difficulty (EASY and DIFF, respectively) were assigned acceptable force ranges of ± 7% and ± 0% of the target force, respectively. To evaluate SICI and ICF in iM1, paired-pulse transcranial magnetic stimulation with 2-ms and 10-ms interstimulus intervals was applied to correct motor-evoked potentials (MEPs) from the first dorsal interosseous muscle during each task. Test stimulus intensity to evoke the MEP with a peak-to-peak amplitude of approximately 0.5–1.5 mV for each task was lower in DIFF than in EASY (P = 0.001), indicating that DIFF increased corticospinal excitability of the ipsilateral hemisphere compared with EASY. The MEPs in SICI and ICF were significantly larger in DIFF than in EASY (P < 0.050). These results suggest that greater corticospinal excitability in the ipsilateral hemisphere during DIFF is associated with reduced SICI and increased ICF.

Movement-Related EEG Oscillations of Contralesional Hemisphere Discloses Compensation Mechanisms of Severely Affected Motor Chronic Stroke Patients.

Conventional rehabilitation strategies for stroke survivors become difficult when voluntary movements are severely disturbed. Combining passive limb mobilization, robotic devices and EEG-based brain-computer interfaces (BCI) systems might improve treatment and clinical follow-up of these patients, but detailed knowledge of neurophysiological mechanisms involved in functional recovery, which might help for tailoring stroke treatment strategies, is lacking. Movement-related EEG changes (EEG event-related desynchronization (ERD) in [Formula: see text] and [Formula: see text] bands, an indicator of motor cortex activation traditionally used for BCI systems), were evaluated in a group of 23 paralyzed chronic stroke patients in two unilateral motor tasks alternating paretic and healthy hands ((i) passive movement, using a hand exoskeleton, and (ii) voluntary movement), and compared to nine healthy subjects. In tasks using unaffected hand, we observed an increase of contralesional hemisphere activation for stroke patients group. Unexpectedly, when using paralyzed hand, motor cortex activation was reduced or absent in severely affected group of patients, while patients with moderate motor deficit showed an activation greater than control group. Cortical activation was reduced or absent in damaged hemisphere of all the patients in both tasks. Significant differences related to severity of motor deficit were found in the time course of [Formula: see text]-[Formula: see text] bands power ratio in EEG of contralesional hemisphere while moving affected hand. These findings suggest the presence of different compensation mechanisms in contralesional hemisphere of stroke patients related to the grade of motor disability, that might turn quantitative EEG during a movement task, obtained from a BCI system controlling a robotic device included in a rehabilitation task, into a valuable tool for monitoring clinical progression, evaluating recovery, and tailoring treatment of stroke patients.

Bilateral Interference in Motor Performance in Homologous vs. Non-homologous Proximal and Distal Effectors.

Performance of bimanual motor actions requires coordinated and integrated bilateral communication, but in some bimanual tasks, neural interactions and crosstalk might cause bilateral interference. The level of interference probably depends on the proportions of bilateral interneurons connecting homologous areas of the motor cortex in the two hemispheres. The neuromuscular system for proximal muscles has a higher number of bilateral interneurons connecting homologous areas of the motor cortex compared to distal muscles. Based on the differences in neurophysiological organization for proximal vs. distal effectors in the upper extremities, the purpose of the present experiment was to evaluate how the level of bilateral interference depends on whether the bilateral interference task is performed with homologous or non-homologous effectors as the primary task. Fourteen participants first performed a unilateral primary motor task with the dominant arm with (1) proximal and (2) distal controlled joysticks. Performance in the unilateral condition with the dominant arm was compared to the same effector’s performance when two different bilateral interference tasks were performed simultaneously with the non-dominant arm. The two different bilateral interference tasks were subdivided into (1) homologous and (2) non-homologous effectors. The results showed a significant decrease in performance for both proximal and distal controlled joysticks, and this effect was independent of whether the bilateral interference tasks were introduced with homologous or non-homologous effectors. The overall performance decrease as a result of bilateral interference was larger for proximal compared to distal controlled joysticks. Furthermore, a proximal bilateral interference caused a larger performance decrement independent of whether the primary motor task was controlled by a proximal or distal joystick. A novel finding was that the distal joystick performance equally interfered with either homologous (distal bilateral interference) or non-homologous (proximal bilateral interference) interference tasks performed simultaneously. The results indicate that the proximal–distal distinction is an important organismic constraint on motor control and for understanding bilateral communication and interference in general and, in particular, how bilateral interference caused by homologous vs. non-homologous effectors impacts motor performance for proximal and distal effectors. The results seem to map neuroanatomical and neurophysiological differences for these effectors.

Using Modified Equipment in Field Hockey Leads to Positive Transfer of Learning Effect.

Cross-education is the phenomenon in which repeated practice of a unilateral motor task does not only result in performance improvement of the trained limb, but also in the untrained contralateral limb. The aim of this study was to test whether cross-education or positive transfer of learning is also achieved for tasks in which both limbs contribute in different ways by using modified equipment that switches the limbs’ role. To this end, a reverse field hockey stick was used that requires a mirroring of arm and hand use and dominance (i.e., right hand on top of the hockey stick instead of the left hand). Two groups of young skilled female field hockey players participated in a crossover-design, in which participants received four training sessions with a reverse hockey stick followed by four training sessions with a regular hockey stick, or vice versa. In a pre-test, intermediate test (following the first intervention period), a post-test (after the second intervention period) and a retention test, participants’ performance on a field hockey skill test with a regular hockey stick was measured. The results revealed that training with the reversed hockey stick led to significantly increased improvements compared to training with a regular hockey stick. We conclude that modified equipment can be used to exploit positive transfer of learning by switching the limbs’ roles. The findings are discussed by referring to the symmetry preservation principle in dynamic systems theory and have clear practical relevance for field hockey trainers and players seeking to further improve field hockey skills.

Mechanomyography and acceleration show interlimb asymmetries in Parkinson patients without tremor compared to controls during a unilateral motor task

The mechanical muscular oscillations are rarely the objective of investigations regarding the identification of a biomarker for Parkinson’s disease (PD). Therefore, the aim of this study was to investigate whether or not this specific motor output differs between PD patients and controls. The novelty is that patients without tremor are investigated performing a unilateral isometric motor task. The force of armflexors and the forearm acceleration (ACC) were recorded as well as the mechanomyography of the biceps brachii (MMGbi), brachioradialis (MMGbra) and pectoralis major (MMGpect) muscles using a piezoelectric-sensor-based system during a unilateral motor task at 70% of the MVIC. The frequency, a power-frequency-ratio, the amplitude variation, the slope of amplitudes and their interlimb asymmetries were analysed. The results indicate that the oscillatory behavior of muscular output in PD without tremor deviates from controls in some parameters: Significant differences appeared for the power-frequency-ratio (p = 0.001, r = 0.43) and for the amplitude variation (p = 0.003, r = 0.34) of MMGpect. The interlimb asymmetries differed significantly concerning the power-frequency-ratio of MMGbi (p = 0.013, r = 0.42) and MMGbra (p = 0.048, r = 0.39) as well as regarding the mean frequency (p = 0.004, r = 0.48) and amplitude variation of MMGpect (p = 0.033, r = 0.37). The mean (M) and variation coefficient (CV) of slope of ACC differed significantly (M: p = 0.022, r = 0.33; CV: p = 0.004, r = 0.43). All other parameters showed no significant differences between PD and controls. It remains open, if this altered mechanical muscular output is reproducible and specific for PD.

More Pronounced Bimanual Interference in Proximal Compared to Distal Effectors of the Upper Extremities

Bimanual performance depends on effective and modular bilateral communication between the two bodysides. Bilateral neural interactions between the bodysides could cause bimanual interference, and the neuromuscular system for proximal and distal muscles is differently organized, where proximal muscles have more bilateral interneurons at both cortical and spinal level compared to distal muscles. These differences might increase the potential for bimanual interference between proximal arm muscles, because of greater proportions of bilateral interneurons to proximal muscles. The purpose of the present experiment was to evaluate potential differences in bimanual interference between proximal versus distal effectors in the upper extremities. 14 participants first performed a unilateral primary motor task with dominant arm with (1) a proximal and (2) distal controlled joysticks (condition A). Performance in condition A, was compared with the same effector’s performance when a bimanual interference task was performed simultaneously with the non-dominant arm (condition B). The results showed a significant bimanual interference for both the proximal and distal controlled joysticks. Most interestingly, the bimanual interference was larger for the proximal joystick compared to the distal controlled joystick. The increase in spatial accuracy error was higher for the proximal controlled joystick, compared with the distal controlled joystick. These results indicate that the proximal-distal distinction is an important organismic constraint on motor control, and especially for bilateral communication. There seem to be an undesired bilateral interference for both proximal and distal muscles. The interference is higher in the case of proximal effectors compared distal effectors, and the results seem to map the neuroanatomical and neurophysiological differences for these effectors.

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

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

No Differences in Sub-Cortical Motor Region Activity for Knee Motor Control Following Anterior Cruciate Ligament Reconstruction

PURPOSE: Emerging research has indicated that anterior cruciate ligament reconstruction (ACL-R) is associated with neuroplasticity. It has been speculated that these findings may have future implications on rehabilitation and ACL-R outcomes. However, most of this research has focused on cortical plasticity rather than sub-cortical plasticity. The purpose of this project was to determine the effects of ACL-R on sub-cortical portions of the cortical-subcortical motor loop. METHODS: A healthy group of active participants (n=16, age=23.2±3.5 years, height=1.7±0.1 m, weight=69.7±14.3 kg) and a left ACL-R group (n=15, age=21.7±2.7 years, height=1.7±0.1 m, weight=70.4±15.8 kg, 38.1±27.2 months’ post-surgery) were locally recruited. Functional magnetic resonance imaging (fMRI) and T1 structural imaging were performed to analyze brain activation during a unilateral left (involved) 45° knee extension/flexion at a rate of 1.2 Hz for 4 blocks of 30 seconds interspersed with 30 seconds of rest. The right putamen and right sub-thalamic nuclei (STN) served as seed regions, and the two groups were contrasted using a mixed-effects general linear model with a priori cluster threshold of p<.05. RESULTS: Compared to the control group, the ACL-R group displayed no differences in right putamen and right STN activation during the unilateral motor task. CONCLUSION: These results indicate that ACL-R may not influence the motor control loop at the sub-cortical level. Therefore, motor control and motor learning, as it relates to the subcortical structures, may not be affected by ACL-R. As a result, neurorehabilitation after ACL-R should use priming techniques to target specific cortical regions that previous studies have indicated as being affected by ACL-R.

Abnormal subcortical activity in congenital mirror movement disorder with RAD51 mutation

Congenital mirror movement disorder (CMMD) is characterized by unintended, nonsuppressible, homologous mirroring activity contralateral to the movement on the intended side of the body. In healthy controls, unilateral movements are accompanied with predominantly contralateral cortical activity, whereas in CMMD, in line with the abnormal behavior, bilateral cortical activity is observed for unilateral motor tasks. However, task-related activities in subcortical structures, which are known to play critical roles in motor actions, have not been investigated in CMMD previously. We investigated the functional activation patterns of the motor components in CMMD patients. By using linkage analysis and exome sequencing, common mutations were revealed in seven affected individuals from the same family. Next, using functional magnetic resonance imaging (fMRI) we investigated cortical and subcortical activity during manual motor actions in two right-handed affected brothers and sex, age, education, and socioeconomically matched healthy individuals. Genetic analyses revealed heterozygous RAD51 c.401C>T mutation which cosegregated with the phenotype in two affected members of the family. Consistent with previous literature, our fMRI results on these two affected individuals showed that mirror movements were closely related to abnormal cortical activity in M1 and SMA during unimanual movements. Furthermore, we have found previously unknown abnormal task-related activity in subcortical structures. Specifically, we have found increased and bilateral activity during unimanual movements in thalamus, striatum, and globus pallidus in CMMD patients. These findings reveal further neural correlates of CMMD, and may guide our understanding of the critical roles of subcortical structures for unimanual movements in healthy individuals.

Sensorimotor Cortex Neuroplasticity Following Neuromuscular Training Augmented With Real Time Biofeedback

Non-contact anterior cruciate ligament (ACL) injury is associated with motor coordination errors leading to comprised knee positioning and resultant knee loads that exceed ligament structural integrity. The nature of the ACL injury event (non-contact) and typical occurrence during high neurocognitive demand situations indicate a nervous system mechanism underlying the inciting event associated with injury. A better understanding of the neural contribution to ACL injury prevention training may enhance the ability to target the underlying mechanisms associated with injury risk. However, it is unknown what neuroplastic mechanisms contribute to the improved motor control documented after neuromuscular training. PURPOSE: To compare the knee sensorimotor cortex activation level before and after neuromuscular control training. METHODS: Ten high school female soccer participants from the local community (age: 15.7±0.95 years; height: 168.4±4.60 cm; mass: 59.91±5.62 kg.) were included in the analysis. fMRI data were collected during performance of a unilateral knee motor task of the left knee consisting of repeated cycles of extension-flexion before and after neuromuscular training. The activation level (blood oxygen level dependent signal) was calculated within the sensorimotor cortex as the primary region of interest. The neuromuscular training program consisted of 6 weeks of standardized ACL injury prevention training augmented with real time feedback designed to reduce movement related knee injury risk factors. RESULTS: Sensorimotor cortex activation increased after training (cluster data: voxels:1120; p<.0001; z-max: 8.55; MNI coordinate peak voxel:12,-26,80; %signal difference: 0.37±0.81) relative to pre-training. CONCLUSIONS: The sensorimotor increased activation associated with neuromuscular training is similar to motor recovery after injury and after long-duration (weeks) motor skill training. The increased sensorimotor cortex activation indicates the cortical representation may be functionally increased for knee motor control after the focused intervention. Future work with expanded sample sizes will map whole brain connectivity and other brain region activation changes associated with neuromuscular training.

Neuroplasticity Associated With Anterior Cruciate Ligament Reconstruction.

Study Design Controlled laboratory study. Background Anterior cruciate ligament (ACL) injury may result in neuroplastic changes due to lost mechanoreceptors of the ACL and compensations in neuromuscular control. These alterations are not completely understood. Assessing brain function after ACL injury and anterior cruciate ligament reconstruction (ACLR) with functional magnetic resonance imaging provides a means to address this gap in knowledge. Objective To compare differences in brain activation during knee flexion/extension in persons who have undergone ACLR and in matched controls. Methods Fifteen participants who had undergone left ACLR (38.13 ± 27.16 months postsurgery) and 15 healthy controls matched on age, sex, height, mass, extremity dominance, education level, sport participation, and physical activity level participated. Functional magnetic resonance imaging data were obtained during a unilateral knee motor task consisting of repeated cycles of knee flexion and extension. Results Participants who had undergone ACLR had increased activation in the contralateral motor cortex, lingual gyrus, and ipsilateral secondary somatosensory area and diminished activation in the ipsilateral motor cortex and cerebellum when compared to healthy matched controls. Conclusion Brain activation for knee flexion/extension motion may be altered following ACLR. The ACLR brain activation profile may indicate a shift toward a visual-motor strategy as opposed to a sensory-motor strategy to engage in knee movement. Level of Evidence Cohort, level 3. J Orthop Sports Phys Ther 2017;47(3):180-189. Epub 5 Nov 2016. doi:10.2519/jospt.2017.7003.

The Brain-Behavior relationship after Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament injury may induce neural adaptations that are unresolved with conventional reconstruction and rehabilitation techniques. Visual-motor function appears to be a key driver of this neuroplasticity. However, the relationship between the neuroplasticity after ACLR (anterior cruciate ligament reconstruction) and visually perturbed neuromuscular control is unknown. PURPOSE: To determine if a relationship exists between brain activation during knee movement and visually perturbed drop landing neuromuscular control, and if ACLR alters this relationship. METHODS:Participants consisted of 26 recreationally active individuals from the local university community (13 ACLR, 13 control matched on height, mass, extremity dominance, education level, history and current physical activity level). A drop vertical jump was completed to assess functional neuromuscular control (knee flexion and adduction). Stroboscopic eyewear provided a visually perturbed condition. The effect of disrupting visual feedback was calculated with a mean change score from the full vison to the disrupted condition. Brain functional magnetic resonance imaging was collected during a unilateral knee motor task of the involved or matched control knee consisting of repeated cycles of extension-flexion. The percent signal change of the motor cortex and lingual gyrus were calculated and correlated against the stroboscopic effect on knee flexion and adduction. RESULTS:Lingual gyrus activation was correlated with the stroboscopic effect on knee flexion for the ACLR (r=0.582, p=0.037) and control (r=0.688, p=0.009) cohorts. Motor cortex activation was correlated with the stroboscopic effect on knee adduction for only the ACLR (r=0.683, p=0.005) cohort. CONCLUSIONS: The motor neuroplasticity associated with ACLR is moderately related to visually perturbed drop landing neuromuscular control. These findings indicate visual-motor control maybe a driving factor behind neuromuscular control changes after ACLR, and a possible contributing mechanism to the continued poor neuromuscular control despite current therapy. Additional attention to the sensory-motor and visual-motor interaction after injury and during therapy may provide a means to improve neuromuscular therapy.

Bilateral cerebellar activation in unilaterally challenged essential tremor.

BackgroundEssential tremor (ET) is one of the most common hyperkinetic movement disorders. Previous research into the pathophysiology of ET suggested underlying cerebellar abnormalities.ObjectiveIn this study, we added electromyography as an index of tremor intensity to functional Magnetic Resonance Imaging (EMG-fMRI) to study a group of ET patients selected according to strict criteria to achieve maximal homogeneity. With this approach we expected to improve upon the localization of the bilateral cerebellar abnormalities found in earlier fMRI studies.MethodsWe included 21 propranolol sensitive patients, who were not using other tremor medication, with a definite diagnosis of ET defined by the Tremor Investigation Group. Simultaneous EMG-fMRI recordings were performed while patients were off tremor medication. Patients performed unilateral right hand and arm extension, inducing tremor, alternated with relaxation (rest). Twenty-one healthy, age- and sex-matched participants mimicked tremor during right arm extension. EMG power variability at the individual tremor frequency as a measure of tremor intensity variability was used as a regressor, mathematically independent of the block regressor, in the general linear model used for fMRI analysis, to find specific tremor-related activations.ResultsBlock-related activations were found in the classical upper-limb motor network, both for ET patients and healthy participants in motor, premotor and supplementary motor areas. In ET patients, we found tremor-related activations bilaterally in the cerebellum: in left lobules V, VI, VIIb and IX and in right lobules V, VI, VIIIa and b, and in the brainstem. In healthy controls we found simulated tremor-related activations in right cerebellar lobule V.ConclusionsOur results expand on previous findings of bilateral cerebellar involvement in ET. We have identified specific areas in the bilateral somatomotor regions of the cerebellum: lobules V, VI and VIII.

Age-Specific Effects of Mirror-Muscle Activity on Cross-Limb Adaptations Under Mirror and Non-Mirror Visual Feedback Conditions.

Cross-limb transfer (CLT) describes the observation of bilateral performance gains due to unilateral motor practice. Previous research has suggested that CLT may be reduced, or absent, in older adults, possibly due to age-related structural and functional brain changes. Based on research showing increases in CLT due to the provision of mirror visual feedback (MVF) during task execution in young adults, our study aimed to investigate whether MVF can facilitate CLT in older adults, who are known to be more reliant on visual feedback for accurate motor performance. Participants (N = 53) engaged in a short-term training regime (300 movements) involving a ballistic finger task using their dominant hand, while being provided with either visual feedback of their active limb, or a mirror reflection of their active limb (superimposed over the quiescent limb). Performance in both limbs was examined before, during and following the unilateral training. Furthermore, we measured corticospinal excitability (using TMS) at these time points, and assessed muscle activity bilaterally during the task via EMG; these parameters were used to investigate the mechanisms mediating and predicting CLT. Training resulted in significant bilateral performance gains that did not differ as a result of age or visual feedback (both p > 0.1). Training also elicited bilateral increases in corticospinal excitability (p < 0.05). For younger adults, CLT was significantly predicted by performance gains in the trained hand (β = 0.47), whereas for older adults it was significantly predicted by mirror activity in the untrained hand during training (β = 0.60). The present study suggests that older adults are capable of exhibiting CLT to a similar degree to younger adults. The prominent role of mirror activity in the untrained hand for CLT in older adults indicates that bilateral cortical activity during unilateral motor tasks is a compensatory mechanism. In this particular task, MVF did not facilitate the extent of CLT.

Motor Planning and Sensory Neuroplasticity after ACL Reconstruction

Anterior cruciate ligament (ACL) injury and reconstruction may induce brain motor control adaptations that influence function and injury risk. Traditional neuromuscular control assessment and therapy may not adequately address this neuroplasticity. fMRI (functional magnetic resonance imaging) provides a detailed method to asses brain function to bridge this gap in knowledge. PURPOSE: To investigate the degree of unilateral sensory-motor brain activation during knee extension-flexion between a group with knee ACL reconstruction (ACLR) and a healthy matched control group. METHODS: Participants were matched on height, mass, extremity dominance, education level, history and current physical activity level. Six left ACLR (25.5±1.37 years, 1.70±0.13 m, 75.6±19.2 kg, Tegner activity level 6.0 ± 1.5, 23±18 months post-surgery) and 6 matched healthy controls (23.6±3.14 years, 1.75±0.05 m, 73.5±12.24 kg, Tegner activity level 6.0 ± 1.5) participated. The brain fMRI was collected during a unilateral knee motor task consisting of repeated cycles of extension and flexion while lying supine in the MRI scanner. The differences between the ACLR activation and contralateral side were contrasted followed by comparison with the control group with a general linear model fixed-effects analysis a priori threshold at p <.01 corrected. RESULTS: Patients with ACLR had increased activation in the supplementary motor region (z=3.29±1.063, p<.001) and somatosensory cortex (z=4.72±1.576, p<.001) when compared to their contralateral healthy extremity and the matched controls. CONCLUSIONS:The ACLR side had greater sensory and motor planning specific brain activation compared to the contralateral knee and control group. The increased sensory cortex activation may be due to the disrupted afferent signals from the ACLR. The motor planning increase may be in response to the adapted sensory integration and feed-forward compensation to sustain motor output. The relatively stable motor cortex activation across side and group indicates that the task requires the same amount of motor drive regardless of side or group, but ACLR status influences the level of motor cortex input from sensory and planning areas to generate the same output.

Editorial: "From brain to body: the impact of nervous system declines on muscle performance in aging".

Editorial: "From brain to body: the impact of nervous system declines on muscle performance in aging".

Plasticity Induced by Intermittent Theta Burst Stimulation in Bilateral Motor Cortices Is Not Altered in Older Adults

Numerous studies have reported that plasticity induced in the motor cortex by transcranial magnetic stimulation (TMS) is attenuated in older adults. Those investigations, however, have focused solely on the stimulated hemisphere. Compared to young adults, older adults exhibit more widespread activity across bilateral motor cortices during the performance of unilateral motor tasks, suggesting that the manifestation of plasticity might also be altered. To address this question, twenty young (<35 years old) and older adults (>65 years) underwent intermittent theta burst stimulation (iTBS) whilst attending to the hand targeted by the plasticity-inducing procedure. The amplitude of motor evoked potentials (MEPs) elicited by single pulse TMS was used to quantify cortical excitability before and after iTBS. Individual responses to iTBS were highly variable, with half the participants showing an unexpected decrease in cortical excitability. Contrary to predictions, however, there were no age-related differences in the magnitude or manifestation of plasticity across bilateral motor cortices. The findings suggest that advancing age does not influence the capacity for, or manifestation of, plasticity induced by iTBS.

Using functional MRI alone for localization in focal epilepsy.

In the present study, we developed a method for the purpose of localizing epilepsy related hemodynamic foci for patients suffering intractable focal epilepsy using resting state fMRI alone. We studied two groups of subjects: five patients with intractable focal epilepsy, and ten healthy volunteers performing motor tasks. Spatial independent component analysis (ICA) was performed on the fMRI alone data and a set of independent component (IC) selection criteria was developed to identify epilepsy related ICs. The method was then evaluated in the healthy group with motor tasks. In all five surgery patients, there was at least one identified IC concordant with surgical resection. In the motor task study of healthy subjects, our method revealed components with concordant spatial and temporal features as expected from the unilateral motor tasks. These results suggest the lateralization and localization value of fMRI alone in presurgical evaluation for patients with intractable unilateral focal epilepsy. The proposed method is noninvasive in nature and easy to implement. It has the potential to be incorporated in current presurgical workup for the diagnosis of intractable focal epilepsy patients.

Detection of reduced interhemispheric cortical communication during task execution in multiple sclerosis patients using functional near-infrared spectroscopy.

Multiple sclerosis (MS) impairs brain activity through demyelination and loss of axons. Increased brain activity is accompanied by increases in microvascular hemoglobin oxygen saturation (oxygenation) and total hemoglobin, which can be measured using functional near-infrared spectroscopy (fNIRS). Due to the potentially reduced size and integrity of the white matter tracts within the corpus callosum, it may be expected that MS patients have reduced functional communication between the left and right sides of the brain; this could potentially be an indicator of disease progression. To assess interhemispheric communication in MS, we used fNIRS during a unilateral motor task and the resting state. The magnitude of the change in hemoglobin parameters in the motor cortex was significantly reduced in MS patients during the motor task relative to healthy control subjects. There was also a significant decrease in interhemispheric communication between the motor cortices (expressed as coherence) in MS patients compared to controls during the motor task, but not during the resting state. fNIRS assessment of interhemispheric coherence during task execution may be a useful marker in disorders with white matter damage or axonal loss, including MS.

O41: Mirror movements in multiple sclerosis

s of Oral Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 S41 catheters were placed at T3, T6, T11 and L1. The spinal cord was severed at the T8 level. At the T12-T13 and at the T4-T5 level, progressive compression of the spinal cord was performed with a precise compression device using a pair of parallel sticks sequentially shortening their distances 0.5 mm every 2 minutes. Cord-to-cord evoked potentials (EP), D-wave and epidural somatosensory evoked potentials (SEPs) were obtained with each mean of compression. Results: In all the cases cord-to-cord EPs were obtained, in both cranial and caudal segments. Spinal cord compression causes the loss of the cordto-cord EP with a 5mm compression cranial to the lesion, and with a3 mm compression caudal to the lesion. D-wave was capable of detecting injuries above the acute lesion, while epidural SEPs detected the injuries below the lesion. Conclusion: It is possible to perform IOM using appropriate electrophysiologic techniques in patients with acute spinal cord injuries, both above and below the lesion. The spinal cord segments caudal to the lesion are more sensitive to new injuries than those cranial to the lesion. Pathophysiology and genetics of mirror movements O40 Interand intrahemispheric inhibition and their role in mirror movements pathophysiology A. Kulaga, M. Ostrowska, A. Szczudlik University Hospital, Neurology, Cracow, Poland Question: Mirror movements (MM) are unintendend and unaware movements of the limb, which remains at rest, during performing intentional movements with the contralateral one. The fibers running through corpus callosum play an important role in inhibition of contralateral hemisphere during performing unilateral motor tasks. MM occur with higher frequency in patients with pathology of corpus callosum. The aim of this study was to determinate the role of corpus callosum in MM’s generation in patients with central nervous system disorders with involment of pyramidal tract. Methods: Clinical evaluation of MM was performed in patients with motor neuron disease (n=36), multiple sclerosis (n=25), acute ischemic stroke (n=17) and control group (n=31). Then all the studied groups were subjected to transcranial magnetic stimulation (TMS) in order to assess the excitatory and inhibitory functions of motor cortex. Results: The frequency of MM was higher in patients with multiple sclerosis, patients with motor neuron disease and in stroke patients (in limbs without paresis), compared to control group. The duration of ipsilateral silent period (iSP), which reflects the function of corpus callosum, was significantly shorter in patients with motor neuron disease and in damaged hemisphere in stroke patients compared to control group. The lack of iSP in one hemisphere in all patient groups occurred in conjunction with shorter duration of contralateral silent period (cSP), which reflects the intrahemispheric inhibition. Conclusion: The fibers of corpus callosum play an important, but probably not exclusive role in MM’s pathophysiology. An additional shortening of intrahemispheric inhibition contralateral to pathological interhemispheric inhibition may facilitate MM occurance. O41 Mirror movements in multiple sclerosis C. Cabib1, S. Llufriu2, E. Martinez-Heras2, A. Saiz2, J. Valls-Sole3 1Clinic Hospital of Barcelona, EMG Unit, Barcelona, Spain; 2Clinic Hospital of Barcelona and Centre d’Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Center for Neuroinmunology, Neurology Service., Barcelona, Spain; 3Clinic Hospital of Barcelona, EMG Unit, Department of Neurology, Barcelona,