Neural decoding from surface high-density EMG signals: influence of anatomy and synchronization on the number of identified motor units

Oliveira, Daniela Souza de; Casolo, Andrea; Balshaw, Thomas G.; Maeo, Sumiaki; Lanza, Marcel Bahia; Martin, Neil R.W.; Maffulli, Nicola; Kinfe, Thomas M.; Eskofier, Bjoern M.; Folland, Jonathan P.; Farina, Dario; Vecchio, Alessandro Del

doi:10.1088/1741-2552/ac823d

Cited by 26 publications

(17 citation statements)

References 52 publications

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“…Within this work, we show that the decomposition goodness for both EMG and MMG is negatively correlated with the thickness of subcutaneous fat tissue as well as the contraction intensity. This is consistent with decomposition results from experimentally measured surface EMG signals (e.g., de Oliveira et al, 2022, Del Vecchio et al, 2020, Farina et al, 2008, even if other factors may play a role (Taylor et al, 2022).…”

Section: Insights On Muscle-induced Bio-electromagnetic Fieldssupporting

confidence: 89%

High-density magnetomyography is superior over surface electromyography for the decomposition of motor units: a simulation study

Klotz¹,

Lehmann²,

Negro³

et al. 2023

Preprint

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Studying motor units (MUs) is essential for understanding motor control, the detection of neuromuscular disorders and the control of humanmachine interfaces. Individual motor unit firings are currently identified in vivo by decomposing electromyographic (EMG) signals. Due to our body's electric properties, individual motor units can only be separated to a limited extent with surface EMG. Unlike electrical signals, magnetic fields pass through biological tissues without distortion. This physical property and emerging technology of quantum sensors make magnetomyography (MMG) a highly promising methodology. However, the full potential of MMG to study neuromuscular physiology has not yet been explored. In this work, we perform in silico trials that combine a biophysical model of EMG and MMG with state-of-the-art algorithms for the decomposition of motor units. This allows the prediction of an upper-bound for the motor unit decomposition accuracy. It is shown that non-invasive MMG is superior over surface EMG for the robust identification of the discharge patterns of individual motor units. Decomposing MMG instead of EMG increased the number of identifiable motor units by 71 %. Notably, MMG exhibits a less pronounced bias to detect superficial motor units. The presented simulations provide insights into methods to study the neuromuscular system non-invasively and in vivo that would not be easily feasible by other means. Hence, this study provides guidance for the development of novel biomedical technologies.

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Section: Insights On Muscle-induced Bio-electromagnetic Fieldssupporting

confidence: 89%

High-density magnetomyography is superior over surface electromyography for the decomposition of motor units: a simulation study

Klotz¹,

Lehmann²,

Negro³

et al. 2023

Preprint

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“…More older adults were recruited due to the potential for a smaller motor unit yield due to age‐related motor neurone loss (denervation and reinnervation cycle) (Hepple & Rice, 2016 ). Thicker fat tissue between the muscle and electrodes was also expected, which could potentially reduce the motor unit yield (Oliveira et al., 2022 ). The participants had no history of neurological disorders, were free of lower limb musculoskeletal injuries, and were not taking medications that could influence the monoaminergic system, including serotonin or noradrenaline modulators (e.g.…”

Section: Methodsmentioning

confidence: 99%

Facilitation–inhibition control of motor neuronal persistent inward currents in young and older adults

Orssatto

Fernandes

Blazevich

et al. 2022

The Journal of Physiology

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A well‐coordinated facilitation–inhibition control of motor neuronal persistent inward currents (PICs) via diffuse neuromodulation and local inhibition is essential to ensure motor units discharge at required times and frequencies. Present best estimates indicate that PICs are reduced in older adults; however, it is not yet known whether PIC facilitation–inhibition control is also altered with ageing. We investigated the responses of PICs to (i) a remote handgrip contraction, which is believed to diffusely increase serotonergic input onto motor neurones, and (ii) tendon vibration of the antagonist muscle, which elicits reciprocal inhibition, in young and older adults. High‐density surface electromyograms were collected from soleus and tibialis anterior of 18 young and 26 older adults during triangular‐shaped plantar and dorsiflexion contractions to 20% (handgrip experiments) and 30% (vibration experiments) of maximum torque (rise‐decline rate of 2%/s). A paired‐motor‐unit analysis was used to calculate ∆F, which is assumed to be proportional to PIC strength. ΔF increased in both soleus (0.55 peaks per second (pps), 16.0%) and tibialis anterior (0.42 pps, 11.4%) after the handgrip contraction independent of age. Although antagonist tendon vibration reduced ΔF in soleus (0.28 pps, 12.6%) independent of age, less reduction was observed in older (0.42 pps, 10.7%) than young adults (0.72 pps, 17.8%) in tibialis anterior. Our data indicate a preserved ability of older adults to amplify PICs following a remote handgrip contraction, during which increased serotonergic input onto the motor neurones is expected, in both lower leg muscles. However, PIC deactivation in response to reciprocal inhibition was impaired with ageing in tibialis anterior despite being preserved in soleus. Key points Motor neuronal persistent inward currents (PICs) are facilitated via diffuse neuromodulation and deactivated by local inhibition to ensure motor units discharge at required times and frequencies, allowing normal motor behaviour. PIC amplitudes appear to be reduced with ageing; however, it is not known whether PIC facilitation–inhibition control is also altered. Remote handgrip contraction, which should diffusely increase serotonergic input onto motor neurones, facilitated PICs similarly in both soleus and tibialis anterior of young and older adults. Antagonist tendon vibration, which induces reciprocal inhibition, reduced PICs in soleus in both young and older adults but had less effect in tibialis anterior in older adults. Data from lower‐threshold motor units during low‐force contractions suggest that PIC facilitation is preserved with ageing in soleus and tibialis anterior. However, the effect of reciprocal inhibition on the contribution of PICs to motor neurone discharge seems reduced in tibialis anterior but preserved in soleus.

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“…Previous studies, however, have shown similar physiological differences between RT and UT individuals regardless of sex (56). The additional challenge is employing HDsEMG recordings in a female population which typically results in a substantially smaller yield of discerned MU firings (57), possibly because of sex differences in adipose tissue that acts as a biological low-pass filter (58), although the direct comparison of sexes and factors associated with differences in MU yield remains to be investigated. This decomposition challenge should be addressed in future studies examining neuromuscular characteristics of RT and UT individuals of both sexes (59).…”

Section: Discussionmentioning

confidence: 99%

Motor Unit Discharge Characteristics and Conduction Velocity of the Vastii Muscles in Long-Term Resistance-Trained Men

Škarabot

Folland

Forsyth

et al. 2022

Medicine &Amp; Science in Sports &Amp; Exercise

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PurposeAdjustments in motor unit (MU) discharge properties have been shown after short-term resistance training; however, MU adaptations in long-term resistance-trained (RT) individuals are less clear. Here, we concurrently assessed MU discharge characteristics and MU conduction velocity in long-term RT and untrained (UT) men.MethodsMotor unit discharge characteristics (discharge rate, recruitment, and derecruitment threshold) and MU conduction velocity were assessed after the decomposition of high-density electromyograms recorded from vastus lateralis (VL) and vastus medialis (VM) of RT (>3 yr; n = 14) and UT (n = 13) during submaximal and maximal isometric knee extension.ResultsResistance-trained men were on average 42% stronger (maximal voluntary force [MVF], 976.7 ± 85.4 N vs 685.5 ± 123.1 N; P < 0.0001), but exhibited similar relative MU recruitment (VL, 21.3% ± 4.3% vs 21.0% ± 2.3% MVF; VM, 24.5% ± 4.2% vs 22.7% ± 5.3% MVF) and derecruitment thresholds (VL, 20.3% ± 4.3% vs 19.8% ± 2.9% MVF; VM, 24.2% ± 4.8% vs 22.9% ± 3.7% MVF; P ≥ 0.4543). There were also no differences between groups in MU discharge rate at recruitment and derecruitment or at the plateau phase of submaximal contractions (VL, 10.6 ± 1.2 pps vs 10.3 ± 1.5 pps; VM, 10.7 ± 1.6 pps vs 10.8 ± 1.7 pps; P ≥ 0.3028). During maximal contractions of a subsample population (10 RT, 9 UT), MU discharge rate was also similar in RT compared with UT (VL, 21.1 ± 4.1 pps vs 14.0 ± 4.5 pps; VM, 19.5 ± 5.0 pps vs 17.0 ± 6.3 pps; P = 0.7173). Motor unit conduction velocity was greater in RT compared with UT individuals in both VL (4.9 ± 0.5 m·s−1 vs 4.5 ± 0.3 m·s−1; P < 0.0013) and VM (4.8 ± 0.5 m·s−1 vs 4.4 ± 0.3 m·s−1; P < 0.0073).ConclusionsResistance-trained and UT men display similar MU discharge characteristics in the knee extensor muscles during maximal and submaximal contractions. The between-group strength difference is likely explained by superior muscle morphology of RT as suggested by greater MU conduction velocity.

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Neural decoding from surface high-density EMG signals: influence of anatomy and synchronization on the number of identified motor units

Cited by 26 publications

References 52 publications

High-density magnetomyography is superior over surface electromyography for the decomposition of motor units: a simulation study

High-density magnetomyography is superior over surface electromyography for the decomposition of motor units: a simulation study

Facilitation–inhibition control of motor neuronal persistent inward currents in young and older adults

Motor Unit Discharge Characteristics and Conduction Velocity of the Vastii Muscles in Long-Term Resistance-Trained Men

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