Mapping Of Primary Motor Cortex Research Articles

EMG-projected MEG high-resolution source imaging of human motor execution: Brain-muscle coupling above movement frequencies

Abstract Magnetoencephalography (MEG) is a non-invasive functional imaging technique for pre-surgical mapping. However, movement-related MEG functional mapping of primary motor cortex (M1) has been challenging in presurgical patients with brain lesions and sensorimotor dysfunction due to the large numbers of trials needed to obtain adequate signal to noise. Moreover, it is not fully understood how effective the brain communication is with the muscles at frequencies above the movement frequency and its harmonics. We developed a novel Electromyography (EMG)-projected MEG source imaging technique for localizing early-stage (-100 to 0 ms) M1 activity during ~l min recordings of left and right self-paced finger movements (~1 Hz). High-resolution MEG source images were obtained by projecting M1 activity towards the skin EMG signal without trial averaging. We studied delta (1-4 Hz), theta (4-7 Hz), alpha (8-12 Hz), beta (15-30 Hz), gamma (30-90 Hz), and upper-gamma (60-90 Hz) bands in 13 healthy participants (26 datasets) and three presurgical patients with sensorimotor dysfunction. In healthy participants, EMG-projected MEG accurately localized M1 with high accuracy in delta (100.0%), theta (100.0%), and beta (76.9%) bands, but not alpha (34.6%) or gamma/upper-gamma (0.0%) bands. Except for delta, all other frequency bands were above the movement frequency and its harmonics. In three presurgical patients, M1 activity in the affected hemisphere was also accurately localized, despite highly irregular EMG movement patterns in one patient. Altogether, our EMG-projected MEG imaging approach is highly accurate and feasible for M1 mapping in presurgical patients. The results also provide insight into movement-related brain-muscle coupling above the movement frequency and its harmonics.

Surgical treatment of epilepsy in children with focal cortical dysplasia in central gyri

Assessment of the outcome after epilepsy surgery in children with FCD in central lobules. Nine patients, median age 3.7 ys, IQR=5.7 ys (min 1.8- max 15.7 ys) with FCD in central gyri and DR-epilepsy underwent surgery. Standard preoperative evaluation included MRI and video-EEG. Invasive recordings were used in 2 cases, coupled by fMRI in 2. An ECOG and neuronavigation, as well as stimulation and mapping of primary motor cortex were used routinely during the procedure. Gross total resection was achieved in 7 patients according to postoperative MRI. Six patients with new or worsening of already existing hemiparesis recovered within a year after surgery. At the last FU (med 5 ys) favorable outcome (Engel class IA) has been achieved in 6 cases (66.7%), while two patients with persisting seizures reported seizing less frequently (Engel II-III). Three patients were able to discontinue AED-treatment and four children resumed development with improvement in cognition and behavior.

P467: Combined neurophysiological and imaging assessment of motor cortical areas in EPM1A patients

s of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339 S173 reviewed. A test was defined as successful if the patients’ habitual attacks were captured. Results: Ten patients were identified who had a repeat HVT following unsuccessful inpatient video-telemetry. In 4/10 patients repeat HVT captured their habitual episodes (40%). Conclusion: Investigation with repeat HVT captured the habitual attacks in 40% of patients compared to 8% with repeat inpatient VTs. These results suggest that if repeat telemetry is required, HVT is the most successful option to capture habitual attacks. Further work is needed to confirm diagnostic accuracy and utility of HVT considering parameters such as age and nature of disease (epileptic v. non-epileptic attacks). P467 Combined neurophysiological and imaging assessment of motor cortical areas in EPM1A patients E. Visani1, L. Canafoglia1, D. Rossi Sebastiano1, V. Contarino2, L. D’Incerti2, F. Panzica1, S. Franceschetti1 1Fondazione IRCCS Carlo Besta, Neurophysiology, Milan, Italy; 2Fondazione IRCCS Carlo Besta, Neuroradiology, Milan, Italy Question: To assess functional organization of the motor cortex in patients with cortical myoclonus due to Unverricht-Lundborg disease (EPM1A) using multimodal neurophysiologic and imaging approach. Methods: Seven healthy subjects and nine EPM1A patients were enrolled in the study. TMS-based mapping of primary motor cortex of the hand associated to real-time frameless neuronavigation system was performed. fMRI activation maps related to hand motor task was obtained. Cortical thickness (CTH) analysis were applied on T1-weighted 3D images. Results: Bilaterally resting motor threshold was significantly higher and mean amplitude of the motor evoked potentials was significantly lower in the patients with respect to healthy subjects. There were no differences between groups in the extension of the cortical representation of the ABP muscle, but bilaterally the centers of gravity (CoGs) of EPM1A patients (Fig. 1, filled circles) lied posteriorly than that of healthy subjects (Fig. 1, crossed circles). fMRI did not revealed significant differences between groups, although a slightly posterior localization of activated cluster was found in patients (Fig. 2A, red cluster) with respect to healthy subjects (Fig. 2A, blue cluster). CTH analysis revealed significant alterations in both precentral and paracentral areas bilaterally, resulting in a thinning of these areas in EPM1A patients (Fig. 2B).

Representation of cricothyroid muscles at the primary motor cortex (M1) in healthy subjects, mapped by navigated transcranial magnetic stimulation (nTMS)

ObjectivesTo establish a methodology for mapping of primary motor cortex (M1) for cricothyroid (CTHY) muscles in a group of healthy subjects using three-dimensional (3D) magnetic resonance imaging (MRI) navigated transcranial magnetic stimulation (nTMS). MethodsTwo independent measurements were performed. Twelve right-handed healthy subjects were included in the study. In the first measurement, mapping of the abductor pollicis brevis (APB) muscle was followed by mapping of the M1 for CTHY. This was performed in 11 subjects. Second, to avoid bias concerning using a hand knob as a landmark, mapping of M1 for CTHY muscle was followed by mapping of M1 for APB. This was performed in three healthy subjects.The nTMS was used, with selective recordings of motor evoked potentials (MEPs) from APB muscle and corticobulbar motor evoked potentials (CoMEPs) from the CTHY muscle. For recording the responses from the CTHY muscle two hook wire electrodes (the size of 76 μm of diametre passing through 27 gauge needle) were inserted in the muscle. For the recording of MEPs from APB muscle, surface electrodes were used. ResultsFirst measurement: Stimulation over the left M1 for APB muscles elicits MEPs in the contralateral APB muscle with a mean latency of 22.8±1.69ms. Stimulation over the left M1 for the CTHY muscle elicits CoMEPs in the contralateral CTHY muscle with a mean latency of 11.89±1.26ms. The distance between the cortical representation for APB and CTHY was 25.19±6.52mm, with CTHY muscle representation lateral to the APB muscle.Second measurement: The results of second measurement of the distance between M1 for CTHY and M1 for APB and their cortical localisation were comparable to the results of the first measurement. ConclusionThis is the first study with the aim to determine the exact cortical localisation of CTHY muscle with nTMS. Mapping of M1 for CTHY and APB muscles by nTMS was successfully performed in all healthy subjects. The exact location of the stimulating points over M1 muscles eliciting responses in CTHY and APB muscles was determined and superimposed over 3D MRI images. The data show that M1 for CTHY muscle is about 25mm more lateral with regard to M1 for the APB muscle. SignificanceMapping of M1 for CTHY muscle might represent an important neurophysiologic marker for facilitating preoperative mapping of motor speech-related cortical areas due to the proximity of motor cortical representation for laryngeal muscles and opercular part of the Broca area.

Motor learning transiently changes cortical somatotopy

Learning a complex motor skill is associated with changes in motor cortex representations of trained body parts. It has been suggested that representation changes reflect the storage of a skill, i.e., the motor memory trace. If a reflection of the trace, such modifications should persist after training is stopped for as long as the skill is retained. The objective here was to test the persistence of learning-related changes in the representation of the forelimb of the rat after learning a reaching task using repeated epidural stimulation mapping of primary motor cortex. It is shown that the forelimb representations enlarge after 8 days of training (n=8) but contract while performing arm movements without learning (n=7, p=0.006); hindlimb representations remain unchanged. Enlargement correlated with learning success (r=0.82; p=0.012). Subsequently, after 8 days without training, representation size reverted to baseline while the motor skill was retained. Somatotopy remained unaltered by a second training phase in which performance did not improve further (n=5). These findings suggest that successful acquisition but not storage of a motor skill depends on cortical map changes. The motor memory trace in rats may require changes in motor cortex organization other than those detected by stimulation mapping.

Somatotopic mapping of the human primary motor cortex with functional magnetic resonance imaging.

We applied functional magnetic resonance imaging (FMRI) to map the somatotopic organization of the primary motor cortex using voluntary movements of the hand, arm, and foot. Eight right-handed healthy subjects performed self-paced, repetitive, flexion/extension movements of the limbs while undergoing echo-planar imaging. Four subjects performed movements of the right fingers and toes, while the remaining subjects performed movements of the right fingers and elbow joint. There was statistically significant functional activity in the left primary motor cortex in all subjects. The pattern of functional activity followed a topographic representation: finger movements resulted in signal intensity changes over the convexity of the left motor cortex, whereas toe movements produced changes either at the interhemispheric fissure or on the dorsolateral surface adjacent to the interhemispheric fissure. Elbow movements overlapped the more medial signal intensity changes observed with finger movements. Functionally active regions were confined to the cortical ribbon and followed the gyral anatomy closely. These findings indicate that FMRI is capable of generating somatotopic maps of the primary motor cortex in individual subjects.