Preference of Personal to Extrapersonal Space in a Visuomotor Task

The speed of visually triggered movements depends, among other things, on the time needed for visuomotor transformations. We show that it takes on average 20–40 msec less time to respond to visual stimuli when they are projected on the reacting fingers than a few centimeters away from them. The result implies significant preference of the personal space to the extrapersonal space for stimuli used in the initiation of visually triggered movements.Peer reviewe

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

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)

Independent component approach to the analysis of EEG and MEG recordings

Multichannel recordings of the electromagnetic fields emerging from neural currents in the brain generate large amounts of data. Suitable feature extraction methods are, therefore, useful to facilitate the representation and interpretation of the data. Recently developed independent component analysis (ICA) has been shown to be an efficient tool for artifact identification and extraction from electroencephalographic (EEG) and magnetoen- cephalographic (MEG) recordings. In addition, ICA has been ap- plied to the analysis of brain signals evoked by sensory stimuli. This paper reviews our recent results in this field

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

Simultaneous EEG and fMRI: T1-based evaluation of heating in a gel phantom at 3 Tesla

EEG electrodes and leads, comparable to metallic implants, can lead to heating of tissue when used in an MRI scanner. Simultaneous EEG and fMRI experiments are frequently carried out at 3 T or higher fields. High field strength, and thus high-energy RF pulses, added to complex EEG lead configuration increases the risk of severe localized heating, or hot spots. Unlike the skin, the brain lacks thermoreceptors, and the subject might not report anything unusual during the scan although hot spots may occur. In simultaneous EEG and fMRI experiments, the temperature at individual electrode sites can be monitored using optic fibre temperature probes. To complement the isolated surface temperature readings, we aimed to map the whole temperature distribution within a phantom. An EEG-equipped gel phantom was imaged using a T1-weighted sequence before and after running a high-energy MR sequence at 3 T. Changes in T1 intensity profile would indicate a relative temperature increase. In our setting, hot spots were not detected in the relative temperature maps of the phantom. Optic fibre temperature probes at selected electrode sites indicated small temperature increases depending on the MR sequence used. The phantom core temperature remained unchanged. RF energy distribution can vary with electrode configurations and MRI scanners. We suggest that EEG equipments should be tested for safety reasons. The MRI thermometry –inspired relative T1 intensity method provides an easy way to test possible heating within a phantom

Ultra-High Field MRI: Transition to Human 7 T in Finland - Workshop Memorandum

A workshop “Ultra-High Field MRI: Transition to Human 7 T in Finland” was organized at Aalto University on October 8–9, 2015. The organizers included Aalto University School of Science, Finnish Infrastructures for Functional Imaging (FIFI), Aalto NeuroImaging (ANI), Aalto Brain Centre (ABC), and Department of Neuroscience and Biomedical Engineering (NBE). The purpose of the workshop was to demonstrate scientific achievements and possibilities enabled by ultra-high field (UHF) magnetic resonance imaging (MRI). The meeting brought together a group of top-level scientists for two days to give presentations and immerse in discussions. This memorandum not only documents the meeting but also paves the way for making the first human 7 T scanner operational in Finland in the near future

Speech‑derived haptic stimulation enhances speech recognition in a multi‑talker background

Published: 03 October 2023Speech understanding, while effortless in quiet conditions, is challenging in noisy environments. Previous studies have revealed that a feasible approach to supplement speech-in-noise (SiN) perception consists in presenting speech-derived signals as haptic input. In the current study, we investigated whether the presentation of a vibrotactile signal derived from the speech temporal envelope can improve SiN intelligibility in a multi-talker background for untrained, normal-hearing listeners. We also determined if vibrotactile sensitivity, evaluated using vibrotactile detection thresholds, modulates the extent of audio-tactile SiN improvement. In practice, we measured participants’ speech recognition in a multi-talker noise without (audio-only) and with (audio-tactile) concurrent vibrotactile stimulation delivered in three schemes: to the left or right palm, or to both. Averaged across the three stimulation delivery schemes, the vibrotactile stimulation led to a significant improvement of 0.41 dB in SiN recognition when compared to the audio-only condition. Notably, there were no significant differences observed between the improvements in these delivery schemes. In addition, audio-tactile SiN benefit was significantly predicted by participants’ vibrotactile threshold levels and unimodal (audio-only) SiN performance. The extent of the improvement afforded by speech-envelope-derived vibrotactile stimulation was in line with previously uncovered vibrotactile enhancements of SiN perception in untrained listeners with no known hearing impairment. Overall, these results highlight the potential of concurrent vibrotactile stimulation to improve SiN recognition, especially in individuals with poor SiN perception abilities, and tentatively more so with increasing tactile sensitivity. Moreover, they lend support to the multimodal accounts of speech perception and research on tactile speech aid devices.I. Sabina Răutu is supported by the Fonds pour la formation à la recherche dans l’industrie et l’agriculture (FRIA), Fonds de la Recherche Scientifique (FRS-FNRS), Brussels, Belgium. Xavier De Tiège is Clinical Researcher at the FRS-FNRS. This research project has been supported by the Fonds Erasme (Research convention “Les Voies du Savoir 2”, Brussels, Belgium)

Comparing MEG and EEG in detecting the ∼20-Hz rhythm modulation to tactile and proprioceptive stimulation

Modulation of the ∼20-Hz brain rhythm has been used to evaluate the functional state of the sensorimotor cortex both in healthy subjects and patients, such as stroke patients. The ∼20-Hz brain rhythm can be detected by both magnetoencephalography (MEG) and electroencephalography (EEG), but the comparability of these methods has not been evaluated. Here, we compare these two methods in the evaluating of ∼20-Hz activity modulation to somatosensory stimuli. Rhythmic ∼20-Hz activity during separate tactile and proprioceptive stimulation of the right and left index finger was recorded simultaneously with MEG and EEG in twenty-four healthy participants. Both tactile and proprioceptive stimulus produced a clear suppression at 300–350 ms followed by a subsequent rebound at 700–900 ms after stimulus onset, detected at similar latencies both with MEG and EEG. The relative amplitudes of suppression and rebound correlated strongly between MEG and EEG recordings. However, the relative strength of suppression and rebound in the contralateral hemisphere (with respect to the stimulated hand) was significantly stronger in MEG than in EEG recordings. Our results indicate that MEG recordings produced signals with higher signal-to-noise ratio than EEG, favoring MEG as an optimal tool for studies evaluating sensorimotor cortical functions. However, the strong correlation between MEG and EEG results encourages the use of EEG when translating studies to clinical practice. The clear advantage of EEG is the availability of the method in hospitals and bed-side measurements at the acute phase.Peer reviewe