Reproducibility of corticokinematic coherence

Corticokinematic coherence (CKC) between limb kinematics and magnetoencephalographic (MEG) signals reflects cortical processing of proprioceptive afference. However, it is unclear whether strength of CKC is reproducible across measurement sessions. We thus examined reproducibility of CKC in a follow-up study. Thirteen healthy right-handed volunteers (7 females, 21.7 +/- 4.3 yrs) were measured using MEG in two separate sessions 12.6 +/- 1.3 months apart. The participant was seated and relaxed while his/her dominant or non-dominant index finger was continuously moved at 3 Hz (4 min for each hand) using a pneumatic movement actuator. Finger kinematics were recorded with a 3-axis accelerometer. Coherence was computed between finger acceleration and MEG signals. CKC strength was defined as the peak coherence value at 3 Hz form a single sensor among 40 pre-selected Rolandic gradiometers contralateral to the movement. Pneumatic movement actuator provided stable proprioceptive stimuli and significant CKC responses peaking at the contralateral Rolandic sensors. In the group level, CKC strength did not differ between the sessions in dominant (Day-1 0.40 +/- 0.19 vs. Day-2 0.41 +/- 0.17) or non-dominant (0.35 +/- 0.16 vs. 0.36 +/- 0.17) hand, nor between the hands. Intraclass-correlation coefficient (ICC) values indicated excellent inter-session reproducibility for CKC strength for both dominant (0.86) and non-dominant (0.97) hand. However, some participants showed pronounced inter-session variability in CKC strength, but only for the dominant hand. CKC is a promising tool to study proprioception in long-term longitudinal studies in the group level to follow, e.g., integrity of cortical proprioceptive processing with motor functions after stroke.Peer reviewe

Quantification of cortical proprioceptive processing through a wireless and miniaturized EEG amplifier

Corticokinematic coherence (CKC) is computed between limb kinematics and cortical activity (e.g. MEG, EEG), and it can be used to detect, quantify and localize the cortical processing of proprioceptive afference arising from the body. EEG-based studies on CKC have been limited to lab environments due to bulky, non-portable instrumentations. We recently proposed a wireless and miniaturized EEG acquisition system aimed at enabling EEG studies outside the laboratory. The purpose of this work is to compare the EEG-based CKC values obtained with this device with a conventional wired-EEG acquisition system to validate its use in the quantification of cortical proprioceptive processing. Eleven healthy right-handed participants were recruited (six males, four females, age range: 24-40 yr). A pneumatic-movement actuator was used to evoke right index-finger flexion-extension movement at 3 Hz for 4 min. The task was repeated both with the wireless-EEG and wired-EEG devices using the same 30-channel EEG cap preparation. CKC was computed between the EEG and finger acceleration. CKC peaked at the movement frequency and its harmonics, being statistically significant (p < 0.05) in 8-10 out of 11 participants. No statistically significant differences (p < 0.05) were found in CKC strength between wireless-EEG (range 0.03-0.22) and wired-EEG (0.02-0.33) systems, that showed a good agreement between the recording systems (3 Hz: r = 0.57, p = 0.071, 6 Hz: r = 0.82, p = 0.003). As expected, CKC peaked in sensors above the left primary sensorimotor cortex contralateral to the moved right index finger. As the wired-EEG device, the tested wireless-EEG system has proven feasible to quantify CKC, and thus can be used as a tool to study proprioception in the human neocortex. Thanks to its portability, the wireless-EEG used in this study has the potential to enable the examination of cortical proprioception in more naturalistic conditions outside the laboratory environment. Clinical Relevance - Our study will contribute to provide innovative technological foundations for future unobtrusive EEG recordings in naturalistic conditions to examine human sensorimotor system

Sensorimotor Mapping With MEG: An Update on the Current State of Clinical Research and Practice With Considerations for Clinical Practice Guidelines

Published: November 2020In this article, we present the clinical indications and advances in the use of magnetoencephalography to map the primary sensorimotor (SM1) cortex in neurosurgical patients noninvasively. We emphasize the advantages of magnetoencephalography over sensorimotor mapping using functional magnetic resonance imaging. Recommendations to the referring physicians and the clinical magnetoencephalographers to achieve appropriate sensorimotor cortex mapping using magnetoencephalography are proposed. We finally provide some practical advice for the use of corticomuscular coherence, corticokinematic coherence, and mu rhythm suppression in this indication. Magnetoencephalography should now be considered as a method of reference for presurgical functional mapping of the sensorimotor cortex.X. De Ti ege is Post-doctorate Clinical Master Specialist at the Fonds de la Recherche Scientifique (FRS-FNRS, Brussels, Belgium). M. Bourguignon has been supported by the program Attract of Innoviris (Grant 2015-BB2B-10), by the Spanish Ministry of Economy and Competitiveness (Grant PSI2016- 77175-P), and by the Marie Sk1odowska-Curie Action of the European Commission (Grant 743562). H. Piitulainen has been supported by the Academy of Finland (Grants #266133 and #296240), the Jane and Aatos Erkko Foundation, and the Emil Aaltonen Foundation. The authors thank Professor Riitta Hari for her support in most of the research works published by the authors and presented in this article. The MEG project at the CUB H^opital Erasme is financially supported by the Fonds Erasme (Research convention “Les Voies du Savoir,” Fonds Erasme, Brussels, Belgium)

Effect of interstimulus interval on cortical proprioceptive responses to passive finger movements

Accepted manuscript online: 28 October 2016Shortening of the interstimulus interval (ISI) generally leads to attenuation of cortical sensory responses. For proprioception, however, this ISI effect is still poorly known. Our aim was to characterize the ISI dependence of movement-evoked proprioceptive cortical responses and to find the optimum ISI for proprioceptive stimulation. We measured, from 15 healthy adults, magnetoencephalographic responses to passive flexion and extension movements of the right index finger. The movements were generated by a movement actuator at fixed ISIs of 0.5, 1, 2, 4, 8, and 16 s, in separate blocks. The responses peaked at ~ 70 ms (extension) and ~ 90 ms (flexion) in the contralateral primary somatosensory cortex. The strength of the cortical source increased with the ISI, plateauing at the 8-s ISI. Modeling the ISI dependence with an exponential saturation function revealed response lifetimes of 1.3 s (extension) and 2.2 s (flexion), implying that the maximum signal-to-noise ratio (SNR) in a given measurement time is achieved with ISIs of 1.7 s and 2.8 s respectively. We conclude that ISIs of 1.5–3 s should be used to maximize SNR in recordings of proprioceptive cortical responses to passive finger movements. Our findings can benefit the assessment of proprioceptive afference in both clinical and research settings.This work was supported by the Academy of Finland (Grants #131483 and #263800 to Riitta Hari and Grants #266133 and #296240 to Harri Piitulainen), Tekes – the Finnish Funding Agency for Technology and Innovation (Grant 1104/10), the European Research Council (Advanced Grant #232946 to Riitta Hari), the Emil Aaltonen Foundation (Eero Smeds), and the Research Programs Unit of the University of Helsinki (Eero Smeds)

Movement Kinematics Dynamically Modulates the Rolandic ~ 20-Hz Rhythm During Goal-Directed Executed and Observed Hand Actions

First Online: 14 February 2018This study investigates whether movement kinematics modulates similarly the rolandic α and β rhythm amplitude during executed and observed goal-directed hand movements. It also assesses if this modulation relates to the corticokinematic coherence (CKC), which is the coupling observed between cortical activity and movement kinematics during such motor actions. Magnetoencephalography (MEG) signals were recorded from 11 right-handed healthy subjects while they performed or observed an actor performing the same repetitive hand pinching action. Subjects’ and actor’s forefinger movements were monitored with an accelerometer. Coherence was computed between acceleration signals and the amplitude of α (8–12 Hz) or β (15–25 Hz) oscillations. The coherence was also evaluated between source-projected MEG signals and their β amplitude. Coherence was mainly observed between acceleration and the amplitude of β oscillations at movement frequency within bilateral primary sensorimotor (SM1) cortex with no difference between executed and observed movements. Cross-correlation between the amplitude of β oscillations at the SM1 cortex and movement acceleration was maximal when acceleration was delayed by ~ 100 ms, both during movement execution and observation. Coherence between source-projected MEG signals and their β amplitude during movement observation and execution was not significantly different from that during rest. This study shows that observing others’ actions engages in the viewer’s brain similar dynamic modulations of SM1 cortex β rhythm as during action execution. Results support the view that different neural mechanisms might account for this modulation and CKC. These two kinematic-related phenomena might help humans to understand how observed motor actions are actually performed.Xavier De Tiège is Postdoctorate Clinical Master Specialist at the Fonds de la Recherche Scientifique (FRS-FNRS, Brussels, Belgium). This work was supported by the program Attract of Innoviris (Grant 2015-BB2B-10 to Mathieu Bourguignon), the Spanish Ministry of Economy and Competitiveness (Grant PSI2016-77175-P to Mathieu Bourguignon), the Marie Skłodowska-Curie Action of the European Commission (grant #743562 to Mathieu Bourguignon), a “Brains Back to Brussels” grant to Veikko Jousmäki from the Institut d’Encouragement de la Recherche Scientifique et de l’Innovation de Bruxelles (Brussels, Belgium), European Research Council (Advanced Grant #232946 to Riitta Hari), the Fonds de la Recherche Scientifique (FRS-FNRS, Belgium, Research Credits: J009713), and the Academy of Finland (grants #131483 and #263800). The MEG project at the ULB-Hôpital Erasme (Brussels, Belgium) is financially supported by the Fonds Erasme

Cortical Processes Related to Motor Stability and Proprioception in Human Adults and Newborns

Accurate control of motor performance requires close co-operation between the motor and sensory functions of the human nervous system. Proprioceptive information about the positions and movements of one s own body parts needs to be carefully monitored to allow fine-tuning of motor output. At the same time, the brain needs to block the influence of distracting external stimuli, such as movements of other persons and various sounds, on the ongoing movements. My thesis focuses on the cortical processes related to these phenomena. In the first studies of this thesis, we explored motor stability by recording brain and muscle activity with magnetoencephalography (MEG) and electromyography, respectively, from healthy adults who were maintaining a steady finger pinch. We analyzed the effects of simple auditory and visual distractors as well as observed movements of another person on the functional state of the primary motor (MI) cortex. All studied stimuli caused transient enhancement of the coupling between cortical and muscular activity at ~20 Hz, reflecting the maintenance of stable motor output. As expected based on earlier studies, movement observation also caused mirror activation in the MI cortex of the viewer, demonstrated by MEG-power suppression at ~7 and ~15 Hz. Importantly, these two simultaneous but opposite processes occurred at distinct frequency bands, suggesting that they were mediated by different populations of MI neurons. The results might explain how the human brain blocks the effects of external distractors on motor behavior and prevents unintentional imitation of observed movements. The latter part of my thesis focuses on cortical activity evoked by proprioceptive afference in adults and newborns. In adults, we recorded MEG responses to proprioceptive input elicited by passive finger extensions and flexions. The amplitudes of the ~70-ms (extension) and ~90-ms (flexion) responses in the primary somatosensory cortex increased by a factor of ~3 and ~6, respectively, when the interstimulus interval was prolonged from 0.5 to 8 s. These findings suggest an optimum interstimulus interval of 1.5 3.0 s for future applications in research and in the clinic. Finally, we showed using electroencephalography that proprioceptive stimulation with continuous passive hand movements elicits a prominent cortical response already at the neonatal phase. Such a passive-movement-based stimulation method could help assess the integrity of somatosensory pathways in neurologically impaired newborns. This thesis improves understanding of the cortical mechanisms essential for proper motor control. The gained knowledge can ultimately benefit diagnostics, treatment, and follow-up of motor-system impairments ranging from movement disorders to neonatal cerebrovascular problems.Täsmällinen liikkeiden säätely edellyttää tiivistä yhteistyötä aivojen liike- ja aistitoimintojen välillä. Yhtäältä aivojen on tarkasti seurattava asentotunnon (proprioseptiikka) välittämää tietoa eri kehonosien asennoista ja liikkeistä, jotta motoriikan hienosäätely olisi mahdollista. Toisaalta taas aivojen täytyy välttää ulkoisten ärsykkeiden, kuten erilaisten äänten ja vaikkapa ympärillä olevien ihmisten liikkeiden, liiallista vaikutusta ihmisen omiin liikkeisiin. Väitöskirjani paneutuu näihin ilmiöihin liittyviin aivokuoritason toimintoihin. Ensimmäisissä osatöissä tutkimme motorista vakautta ulkoisten häiriöärsykkeiden aikana mittaamalla terveiden aikuisten koehenkilöiden aivo- ja lihastoimintaa magnetoenkefalografialla (MEG) ja elektromyografialla samalla kun he puristivat pinsettiotteella voima-anturia tasaisella, kevyellä voimalla. Esitimme koehenkilöille tehtävän aikana yksinkertaisia kuulo- ja näköärsykkeitä sekä näytimme toisen henkilön käden liikkeitä. Primaarilta liikeaivokuorelta (MI) ja käden lihaksista mitattujen signaalien välillä esiintyvä ~20 Hz:n taajuinen niin kutsuttu kortikomuskulaarinen koherenssi voimistui kaikkien esitettyjen häiriöärsykkeiden jälkeen merkkinä MI alueen toiminnan vakauttamisesta. Toisen henkilön käden liike aiheutti lisäksi peilautumista katsojan omalla MI alueella, kuten jo aiemmissa tutkimuksissa on näytetty. Tästä peilautumisesta osoituksena oli MEG:n tehon vaimeneminen ~7 ja ~15 Hz:n taajuuksilla. Nämä samanaikaiset mutta vastakkaiset prosessit esiintyivät eri taajuuksilla viitaten siihen, että ne olivat lähtöisin eri hermosolupopulaatioista. Tuloksemme voivat selittää sen, kuinka aivot torjuvat ulkoisten häiriöärsykkeiden suorat vaikutukset ihmisen omiin liikkeisiin ja estävät muiden ihmisten liikkeiden tahattoman matkimisen. Väitöskirjani jälkimmäinen osa tarkastelee proprioseptiivisten ärsykkeiden herättämää aivoaktivaatiota aikuisilla ja vastasyntyneillä. Mittasimme aikuisilta passiivisten sormen ojennus- ja koukistusliikkeiden synnyttämiä MEG-vasteita tutkien erityisesti sitä, kuinka liikeärsykkeiden antotiheys vaikuttaa vasteiden voimakkuuteen. Voimakkaimmat vastehuiput esiintyivät primaarilla tuntoaivokuorella ~70 (ojennus) ja ~90 ms (koukistus) liikkeen alun jälkeen, ja niiden amplitudi kasvoi noin kolmin- (ojennus) ja kuusinkertaisiksi (koukistus), kun peräkkäisten liikkeiden välistä aikaa pidennettiin 0.5 sekunnista 8 sekuntiin. Tulosten perusteella optimaalinen liikeärsykkeiden välinen aika näiden aivovasteiden mittaamiseen on 1.5 3 s. Tietoa voidaan hyödyntää tulevissa sovelluksissa niin tutkimuksessa kuin kliinisessäkin työssä. Viimeisessä osatyössä osoitimme, että elektroenkefalografialla voi mitata passiivisen liikkeen synnyttämiä aivovasteita myös vastasyntyneiltä. Tällaisilla mittauksilla voidaan kenties tulevaisuudessa selvittää vastasyntyneiden potilaiden tuntojärjestelmän toimintaa aivovaurioiden ja muiden neurologisten häiriöiden yhteydessä. Väitöskirjani edistää ymmärrystä liikkeiden säätelyyn liittyvistä aivokuoritason mekanismeista. Uusi tieto voi lopulta johtaa parempaan diagnostiikkaan, hoitoon ja seurantaan esimerkiksi liikehäiriöissä sekä vastasyntyneiden aivoverenkiertohäiriöissä

Localization of Sensorimotor Cortex Using Navigated Transcranial Magnetic Stimulation and Magnetoencephalography

The mapping of the sensorimotor cortex gives information about the cortical motor and sensory functions. Typical mapping methods are navigated transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG). The differences between these mapping methods are, however, not fully known. TMS center of gravities (CoGs), MEG somatosensory evoked fields (SEFs), corticomuscular coherence (CMC), and corticokinematic coherence (CKC) were mapped in ten healthy adults. TMS mapping was performed for first dorsal interosseous (FDI) and extensor carpi radialis (ECR) muscles. SEFs were induced by tactile stimulation of the index finger. CMC and CKC were determined as the coherence between MEG signals and the electromyography or accelerometer signals, respectively, during voluntary muscle activity. CMC was mapped during the activation of FDI and ECR muscles separately, whereas CKC was measured during the waving of the index finger at a rate of 3-4 Hz. The maximum CMC was found at beta frequency range, whereas maximum CKC was found at the movement frequency. The mean Euclidean distances between different localizations were within 20 mm. The smallest distance was found between TMS FDI and TMS ECR CoGs and longest between CMC FDI and CMC ECR sites. TMS-inferred localizations (CoGs) were less variable across participants than MEG-inferred localizations (CMC, CKC). On average, SEF locations were 8 mm lateral to the TMS CoGs (p <0.01). No differences between hemispheres were found. Based on the results, TMS appears to be more viable than MEG in locating motor cortical areas.Peer reviewe

Corticokinematic coherence as a new marker for somatosensory afference in newborns

Objective: Somatosensory evoked potentials have high prognostic value in neonatal intensive care, but their recording from infants is challenging. Here, we studied the possibility to elicit cortical responses in newborns by simple passive hand movements. Methods: We examined 13 newborns (postnatal age 1-46 days) during clinically indicated 19-channel electroencephalography (EEG) recordings in the neonatal intensive care unit; EEG indications included birth asphyxia and suspected epileptic seizures. The experimenter moved the infant's wrist or fingers at 1 or 2 Hz for 5-10 min, separately on both sides. We measured movement kinematics with an accelerometer attached to the infant's hand and computed coherence between the EEG and acceleration signals (corticokinematic coherence, CKC). Results: Statistically significant CKC (amplitude 0.020-0.511) with characteristic scalp topography was observed in all infants at twice the movement frequency. CKC was contralaterally dominant on the central scalp (median laterality index 0.48 for right-hand and -0.63 for left-hand movements). Conclusions: Passive movements elicit cortical responses that can be readily observed in clinical EEG recordings from newborns in the intensive-care environment. (C) 2017 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd.Peer reviewe

Proprioceptive and tactile processing in individuals with Friedreich ataxia: an fMRI study

ObjectiveFriedreich ataxia (FA) neuropathology affects dorsal root ganglia, posterior columns in the spinal cord, the spinocerebellar tracts, and cerebellar dentate nuclei. The impact of the somatosensory system on ataxic symptoms remains debated. This study aims to better evaluate the contribution of somatosensory processing to ataxia clinical severity by simultaneously investigating passive movement and tactile pneumatic stimulation in individuals with FA.MethodsTwenty patients with FA and 20 healthy participants were included. All subjects underwent two 6 min block-design functional magnetic resonance imaging (fMRI) paradigms consisting of twelve 30 s alternating blocks (10 brain volumes per block, 120 brain volumes per paradigm) of a tactile oddball paradigm and a passive movement paradigm. Spearman rank correlation tests were used for correlations between BOLD levels and ataxia severity.ResultsThe passive movement paradigm led to the lower activation of primary (cSI) and secondary somatosensory cortices (cSII) in FA compared with healthy subjects (respectively 1.1 ± 0.78 vs. 0.61 ± 1.02, p = 0.04, and 0.69 ± 0.5 vs. 0.3 ± 0.41, p = 0.005). In the tactile paradigm, there was no significant difference between cSI and cSII activation levels in healthy controls and FA (respectively 0.88 ± 0.73 vs. 1.14 ± 0.99, p = 0.33, and 0.54 ± 0.37 vs. 0.55 ± 0.54, p = 0.93). Correlation analysis showed a significant correlation between cSI activation levels in the tactile paradigm and the clinical severity (R = 0.481, p = 0.032).InterpretationOur study captured the difference between tactile and proprioceptive impairments in FA using somatosensory fMRI paradigms. The lack of correlation between the proprioceptive paradigm and ataxia clinical parameters supports a low contribution of afferent ataxia to FA clinical severity

IFCN-endorsed practical guidelines for clinical magnetoencephalography (MEG)

Magnetoencephalography (MEG) records weak magnetic fields outside the human head and thereby provides millisecond-accurate information about neuronal currents supporting human brain function. MEG and electroencephalography (EEG) are closely related complementary methods and should be interpreted together whenever possible. This manuscript covers the basic physical and physiological principles of MEG and discusses the main aspects of state-of-the-art MEG data analysis. We provide guidelines for best practices of patient preparation, stimulus presentation, MEG data collection and analysis, as well as for MEG interpretation in routine clinical examinations. In 2017, about 200 whole-scalp MEG devices were in operation worldwide, many of them located in clinical environments. Yet, the established clinical indications for MEG examinations remain few, mainly restricted to the diagnostics of epilepsy and to preoperative functional evaluation of neurosurgical patients. We are confident that the extensive ongoing basic MEG research indicates potential for the evaluation of neurological and psychiatric syndromes, developmental disorders, and the integrity of cortical brain networks after stroke. Basic and clinical research is, thus, paving way for new clinical applications to be identified by an increasing number of practitioners of MEG. (C) 2018 International Federation of Clinical Neurophysiology. Published by Elsevier B.V.Peer reviewe