Characterizing off-target corticospinal responses to double-cone transcranial magnetic stimulation

Proessl, Felix; Canino, Maria C; Beckner, Meaghan E.; Sinnott, Aaron M.; Eagle, Shawn R.; LaGoy, Alice D.; Conkright, William R.; Sterczala, Adam J.; Connaboy, Chris; Ferrarelli, Fabio; Germain, Anne; Nindl, Bradley C.; Flanagan, Shawn D.

doi:10.1007/s00221-021-06044-5

Cited by 2 publications

(1 citation statement)

References 57 publications

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“…We performed exploratory analyses of TMS‐evoked contralateral MEPs in the non‐target, resting limb with the goal of providing insight into the potential cortical origins of motor overflow. A recent study found that such “off‐target” MEPs are common (Proessl et al, 2021). We found that for both the paretic and non‐paretic limb, the isometric and dynamic conditions had larger non‐target MEPs than the rest condition (indicative of greater corticomotor excitability).…”

Section: Discussionmentioning

confidence: 99%

Motor overflow in the lower limb after stroke: Insights into mechanisms

Cleland

Madhavan

2022

Eur J of Neuroscience

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Motor overflow (involuntary muscle activation) is common after stroke, particularly in the non‐paretic upper limb. Two potential cortical mechanisms are as follows: (1) The contralesional hemisphere controls both limbs, and (2) inhibition from the ipsilesional to the contralesional hemisphere is diminished. Few studies have differentiated between these hypotheses or investigated motor overflow in the lower limb after stroke. To investigate these potential mechanisms, individuals with chronic stroke performed unilateral isometric and dynamic dorsiflexion. Motor overflow was quantified in the contralateral, resting (non‐target) ankle. Transcranial magnetic stimulation (TMS) was applied, and responses were measured in both legs. Relations between motor overflow, excitability of ipsilateral motor pathways, and interhemispheric inhibition were assessed. Non‐target muscle activity (motor overflow) was greater during isometric and dynamic conditions than rest in both legs (p ≤ 0.001) and was higher in the non‐paretic than the paretic leg (p = 0.03). Some participants (25%) had motor overflow >4SD above the group mean in the non‐paretic leg. Greater motor overflow in the non‐paretic leg was associated with lesser inhibition from the ipsilesional to the contralesional hemisphere (p = 0.04). In both legs, non‐target TMS responses were greater during the isometric and dynamic than the rest condition (p ≤ 0.01) but not when normalized to background muscle activity. Overall, motor overflow occurred in both legs after stroke, suggesting a common bilateral mechanism. Our correlational results suggest that alterations in interhemispheric inhibition may contribute to motor overflow. Furthermore, the lack of differences in non‐target motor evoked potentials MEPs between rest, isometric, and dynamic conditions suggests that subcortical and/or spinal pathways may contribute to motor overflow.

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Section: Discussionmentioning

confidence: 99%

Motor overflow in the lower limb after stroke: Insights into mechanisms

Cleland

Madhavan

2022

Eur J of Neuroscience

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Use-dependent corticospinal excitability is associated with resilience and physical performance during simulated military operational stress

Proessl

Canino

Beckner

et al. 2022

Journal of Applied Physiology

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Simulated military operational stress (SMOS) provides a useful model to better understand resilience in humans as the stress associated with caloric restriction, sleep deficits, and fatiguing exertion degrades physical and cognitive performance. Habitual physical activity may confer resilience against these stressors by promoting favorable use-dependent neuroplasticity, but it is unclear how physical activity, resilience, and corticospinal excitability (CSE) relate during SMOS. PURPOSE: To examine associations between corticospinal excitability, physical activity, and physical performance during SMOS. METHODS: Fifty-three service members (age: 26±5yrs, 13 women) completed a five day and night intervention composed of familiarization, baseline, SMOS (two nights/days), and recovery days. During SMOS, participants performed rigorous physical and cognitive activities while receiving half of normal sleep (two 2h blocks) and caloric requirements. Lower and upper limb CSE were determined with transcranial magnetic stimulation (TMS) stimulus-response curves. Self-reported resilience, physical activity, military-specific physical performance (TMT) and endocrine factors were compared in individuals with high (HIGH) and low CSE based on a median split of lower limb CSE at baseline. RESULTS: HIGH had greater physical activity and better TMT performance throughout SMOS. Both groups maintained physical performance despite substantial psychophysiological stress. Physical activity, resilience, and TMT performance were directly associated with lower limb CSE. CONCLUSION: Individual differences in physical activity coincide with lower (but not upper) limb CSE. Such use-dependent corticospinal excitability directly relates to resilience and physical performance during SMOS. Future studies may use non-invasive neuromodulation to clarify the interplay among CSE, physical activity, and resilience and improve physical and cognitive performance.

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Characterizing off-target corticospinal responses to double-cone transcranial magnetic stimulation

Cited by 2 publications

References 57 publications

Motor overflow in the lower limb after stroke: Insights into mechanisms

Motor overflow in the lower limb after stroke: Insights into mechanisms

Use-dependent corticospinal excitability is associated with resilience and physical performance during simulated military operational stress

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