Kleiser, B. | Search bioRxiv

bioRxiv2026

Reliability of Spatiotemporal Neuromuscular Activity Patterns in Magnetomyography Across Force Levels

BackgroundMagnetomyography (MMG) using an optically pumped magnetometer (OPM) provides a contactless and non-invasive approach to assess neuromuscular activity. However, given the limited studies using optically pumped magnetometer magnetomyography (OPM-MMG) and that those primarily used a single OPM, it remains to be characterized how stable individual neuromuscular activity patterns are over time and across different force levels when using multiple OPMs, specifically an array-based MMG. Methods12 healthy subjects performed ramped isometric contractions at 10, 20, 40, 60, and 80% maximal voluntary contraction (MVC), while a 2x3 OPM array recorded MMG signals from the tibialis anterior (TA). For the test-retest reliability, ramps at 20% and 60% MVC were each repeated once. For each subject, Spearmans rank correlation was computed across all OPM sensors between force conditions to assess consistency of feature rankings, and within-subject spatial repeatability between repeated 20% and 60% MVC ramps was quantified using ICC (3,1) (two-way mixed-effects, single-measure, absolute agreement). ResultsIn 9 of 12 subjects, Spearmans rank analyses showed generally high correlations across force levels ({rho} = 0.37 to 0.91, p<0.05), whereas in the remaining 3 subjects, spatial patterns were less stable ({rho} = -0.73 to 0.58, p<0.05). ICC (3,1) between repeated ramps indicated high within-subject spatial repeatability of the array pattern in 9 out of 12 subjects, with ICC > 0.75 at 20% MVC (5 out of 9 subjects) and 60% MVC (6 out of 9 subjects), respectively. In contrast, the remaining 3 subjects showed lower ICCs (20% MVC: -0.28 to 0.51; 60% MVC: 0.22 to 0.80). ConclusionArray-based OPM-MMG shows high within-subject stability of spatial patterns across force levels and strong test-retest repeatability in the majority of subjects (9 out of 12), supporting its use for characterizing force-dependent neuromuscular activity while acknowledging inter-subject variability.

neuroscience↗

bioRxiv2023

Patterns of subregional cerebellar atrophy across epilepsy syndromes: An ENIGMA-Epilepsy study

ObjectiveThe intricate neuroanatomical structure of the cerebellum is of longstanding interest in epilepsy, but has been poorly characterized within the current cortico-centric models of this disease. We quantified cross-sectional regional cerebellar lobule volumes using structural MRI in 1,602 adults with epilepsy and 1,022 healthy controls across twenty-two sites from the global ENIGMA-Epilepsy working group. MethodsA state-of-the-art deep learning-based approach was employed that parcellates the cerebellum into 28 neuroanatomical subregions. Linear mixed models compared total and regional cerebellar volume in i) all epilepsies; ii) temporal lobe epilepsy with hippocampal sclerosis (TLE-HS); iii) non-lesional temporal lobe epilepsy (TLE-NL); iv) genetic generalised epilepsy; and (v) extra-temporal focal epilepsy (ETLE). Relationships were examined for cerebellar volume versus age at seizure onset, duration of epilepsy, phenytoin treatment, and cerebral cortical thickness. ResultsAcross all epilepsies, reduced total cerebellar volume was observed (d=0.42). Maximum volume loss was observed in the corpus medullare (dmax=0.49) and posterior lobe grey matter regions, including bilateral lobules VIIB (dmax= 0.47), Crus I/II (dmax= 0.39), VIIIA (dmax=0.45) and VIIIB (dmax=0.40). Earlier age at seizure onset ({eta}{rho}2max=0.05) and longer epilepsy duration ({eta}{rho}2max=0.06) correlated with reduced volume in these regions. Findings were most pronounced in TLE-HS and ETLE with distinct neuroanatomical profiles observed in the posterior lobe. Phenytoin treatment was associated with reduced posterior lobe volume. Cerebellum volume correlated with cerebral cortical thinning more strongly in the epilepsy cohort than in controls. SignificanceWe provide robust evidence of deep cerebellar and posterior lobe subregional grey matter volume loss in patients with chronic epilepsy. Volume loss was maximal for posterior subregions implicated in non-motor functions, relative to motor regions of both the anterior and posterior lobe. Associations between cerebral and cerebellar changes, and variability of neuroanatomical profiles across epilepsy syndromes argue for more precise incorporation of cerebellum subregions into neurobiological models of epilepsy. Key pointsO_LICerebellar involvement in epilepsy is poorly understood within current cortico-centric models of this disease C_LIO_LIWe used a novel, deep learning segmentation tool to parcellate the cerebellum into 28 anatomical subunits using an international MRI dataset of 1,602 individuals with epilepsy (aged between 18 and 65 years old) including temporal lobe epilepsy with hippocampal sclerosis (TLE-HS, n=562), TLE non-lesional (TLE-NL, n=284), generalised genetic epilepsy (GGE, n=186) and extra temporal focal epilepsy (ETLE, n=251) and 1,022 controls. C_LIO_LIAcross all epilepsies (vs. controls) robust changes in the corpus medullare and posterior lobe "non-motor" regions were observed, with maximal differences in bilateral VIIB and Crus II lobules. Lower volume of these regions correlated with longer disease duration. Anterior "motor lobe" regions were relatively spared. C_LIO_LIFindings were most pronounced in TLE-HS and ETLE groups, with distinct neuroanatomical profiles observed. C_LIO_LICortical thinning was associated with pronounced cerebellar volume loss in TLE-HS epilepsy, relative to controls. C_LI ETHICAL PUBLICATION STATEMENTWe confirm that we have read the Journals position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.

neuroscience↗