Mechanical perturbations can elicit triggered reactions in the absence of a startle response

Forgaard, Christopher J; Franks, Ian M.; Bennett, Kimberly; Maslovat, Dana; Chua, Romeo

doi:10.1007/s00221-017-5134-x

Cited by 5 publications

(3 citation statements)

References 59 publications

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“…It is also known that spinal excitability, as tested through the H-reflex, increases ~25 ms prior to the onset of a voluntary response (MacKinnon and Rothwell, 2000). Given that the fastest voluntary RTs in a compensate task occur during the R3 epoch (Forgaard et al, 2018), the generic R2 increase we have observed on trials with a voluntary response may have resulted from descending modulation of spinal excitability preceding the voluntary response. This mechanism could explain why the R1 response can be facilitated when the voluntary response is temporally cued to occur earlier (Lewis et al, 2006), and why the LLR does not modulate if onset of the voluntary response occurs far beyond the end of this stretch response (Manning et al, 2012).…”

Section: Volition and Llr Facilitationmentioning

confidence: 67%

The influence of kinesthetic motor imagery and effector specificity on the long-latency stretch response

Forgaard

Franks

Maslovat

et al. 2019

Preprint

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New and NoteworthyWe examined volitional modulation of the long-latency stretch response (LLR) using two novel approaches: motor imagery and the execution of contralateral movements. The LLR was only facilitated on imagery or contralateral trials when a voluntary response "leakedout" into stretched muscle suggesting that a voluntary response in the same muscle as the LLR is a prerequisite for facilitation. Our findings also demonstrate an important distinction between the early (R2) and late (R3) portions of the LLR.Feedback response facilitation 2 AbstractThe long-latency "reflexive" response (LLR) following an upper-limb mechanical disturbance is generated by neural circuitry shared with voluntary control. This feedback response supports many task-dependent behaviours and permits the expression of goal-directed corrections at latencies shorter than voluntary reaction time. An extensive body of literature has demonstrated that the LLR shows flexibility akin to voluntary control, but it has never been tested whether instruction-dependent LLR changes can also occur in the absence of an overt voluntary response. The present study used kinesthetic motor imagery (Experiment 1) and instructed participants to execute a voluntary response in a non-stretched contralateral muscle (Experiment 2) to explore the relationship between the overt production of a voluntary response and LLR facilitation. Activity in stretched right wrist flexors were compared to standard "notintervene" and "compensate" conditions. Our findings revealed that on ~40% of imagery and ~50% of contralateral trials, a partial voluntary response "leaked-out" into the stretched right wrist flexor muscle. On these "leaked" trials, the early portion of the LLR (R2) was facilitated and displayed a similar increase to compensate trials. The latter half of the LLR (R3) showed further modulation, mirroring the patterns of voluntary response activity. By contrast, the LLR on "non-leaked" imagery and contralateral trials did not modulate. We suggest that even though a hastened voluntary response cannot account for all instruction-dependent LLR modulation, the overt execution of a voluntary response in the same muscle(s) as the LLR is a pre-requisite for facilitation of this rapid feedback response. Feedback response facilitation

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Section: Volition and Llr Facilitationmentioning

confidence: 67%

The influence of kinesthetic motor imagery and effector specificity on the long-latency stretch response

Forgaard

Franks

Maslovat

et al. 2019

Preprint

Self Cite

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“…EMG activity related to WE was recorded from right extensor carpi radialis muscle (ECR). As the IS can be a source of a startle reaction, surface EMG activity was recorded from the right orbicularis oculi (OOc) and sternocleidomastoid muscles (SCM), which are considered “startle indicator muscles” (Carlsen et al 2011 ; Forgaard et al 2018 ). Filter settings were 10–10,000 Hz.…”

Section: Methodsmentioning

confidence: 99%

The benefit of knowledge: postural response modulation by foreknowledge of equilibrium perturbation in an upper limb task

Castellote,

Kofler,

Mayr

2023

Eur J Appl Physiol

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For whole-body sway patterns, a compound motor response following an external stimulus may comprise reflexes, postural adjustments (anticipatory or compensatory), and voluntary muscular activity. Responses to equilibrium destabilization may depend on both motor set and a subject`s expectation of the disturbing stimulus. To disentangle these influences on lower limb responses, we studied a model in which subjects (n = 14) were suspended in the air, without foot support, and performed a fast unilateral wrist extension (WE) in response to a passive knee flexion (KF) delivered by a robot. To characterize the responses, electromyographic activity of rectus femoris and reactive leg torque was obtained bilaterally in a series of trials, with or without the requirement of WE (motor set), and/or beforehand information about the upcoming velocity of KF (subject`s expectation). Some fast-velocity trials resulted in StartReact responses, which were used to subclassify leg responses. When subjects were uninformed about the upcoming KF, large rectus femoris responses concurred with a postural reaction in conditions without motor task, and with both postural reaction and postural adjustment when WE was required. WE in response to a low-volume acoustic signal elicited no postural adjustments. When subjects were informed about KF velocity and had to perform WE, large rectus femoris responses corresponded to anticipatory postural adjustment rather than postural reaction. In conclusion, when subjects are suspended in the air and have to respond with WE, the prepared motor set includes anticipatory postural adjustments if KF velocity is known, and additional postural reactions if KF velocity is unknown.

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“…Current evidence suggests that the RST is responsible for the increase in the LLR when participants are instructed to resist a perturbation rather than yield (3). Additionally, the StartReact experimental paradigm has shown to elicit a faster than normal planned voluntary EMG response ( ∼ 70 ms post perturbation onset) in the presence of a startling acoustic stimulus prior to a perturbation (19, 20). The decrease in the voluntary response latency is likely contributed by the RST as the only supraspinal pathway able to act with such a short response time (21, 19, 16).…”

Section: Introductionmentioning

confidence: 99%

Inhibitory Effect of Subthreshold TMS on the Long-Latency Response in the Flexor Carpi Radialis

Helm,

Sergi

2024

Preprint

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The corticospinal pathway and several secondary motor pathways contribute to long-latency responses(LLRs). While evidence of the contribution of secondary motor pathways to LLRs is available, it is unknown if these pathways can produce LLRs independently from corticospinal input. Transcranial magnetic stimulation(TMS) can modulate corticospinal excitability during the LLR. Subthreshold TMS would be ideal for inhibition of corticospinal excitability as it would allow to study function of secondary motor pathways using functional imaging methods with low temporal resolution with minimal activation confound. However, the subthreshold TMS parameters that maximally inhibit corticospinal activity are unknown. In this study, twenty-four participants performed a protocol that combined surface electromyography(EMG), robot-evoked wrist perturbations, and subthreshold TMS applied to the motor cortex to study the effect of TMS intensity and latency on the LLR amplitude in the flexor carpi radialis. We tested two TMS intensities of 90% and 95% AMT and three different latencies, defined such that the motor evoked potential (MEP) peak would arrive at 0 ms, 20 ms, or 50 ms prior to perturbation onset (T_1, T_2, T_3, respectively). Subthreshold TMS significantly reduced the LLR amplitude when applied with T_2 (padj=0.0330) and T_3 latencies (padj=0.0002). Overall, our findings indicate that single-pulse, subthreshold TMS delivered to evoke an MEP with timing comprised between 20 ms and 50 ms prior to perturbation onset significantly reduce the corticospinal component of the LLR. The outcome of this work can be used to inform functional neuroimaging protocols to study the causal role of secondary motor pathways on LLRs.

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Mechanical perturbations can elicit triggered reactions in the absence of a startle response

Cited by 5 publications

References 59 publications

The influence of kinesthetic motor imagery and effector specificity on the long-latency stretch response

The influence of kinesthetic motor imagery and effector specificity on the long-latency stretch response

The benefit of knowledge: postural response modulation by foreknowledge of equilibrium perturbation in an upper limb task

Inhibitory Effect of Subthreshold TMS on the Long-Latency Response in the Flexor Carpi Radialis

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