Voluntary reaction time and long-latency reflex modulation

Forgaard, Christopher J; Franks, Ian M.; Maslovat, Dana; Chin, Laurence; Chua, Romeo

doi:10.1152/jn.00648.2015

Cited by 25 publications

(30 citation statements)

References 46 publications

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“…Furthermore, all these studies explored motor responses in the same passively displaced limb during the time window of LLR [34, 56, 57, 61]. Hence it was difficult to ascertain the suspected startling nature of kinematic stimuli, and, if startle signs were present in OOc or SCM, the superimposition of reflexive or voluntary responses in the limb being moved made a clear characterization of startle responses in the same extremity muscles difficult.…”

Section: Discussionmentioning

confidence: 99%

Evidence for Startle Effects due to Externally Induced Lower Limb Movements: Implications in Neurorehabilitation

Castellote

Kofler²,

Mayr³

et al. 2017

BioMed Research International

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Passive limb displacement is routinely used to assess muscle tone. If we attempt to quantify muscle stiffness using mechanical devices, it is important to know whether kinematic stimuli are able to trigger startle reactions. Whether kinematic stimuli are able to elicit a startle reflex and to accelerate prepared voluntary movements (StartReact effect) has not been studied extensively to date. Eleven healthy subjects were suspended in an exoskeleton and were exposed to passive left knee flexion (KF) at three intensities, occasionally replaced by fast right KF. Upon perceiving the movement subjects were asked to perform right wrist extension (WE), assessed by extensor carpi radialis (ECR) electromyographic activity. ECR latencies were shortest in fast trials. Startle responses were present in most fast trials, yet being significantly accelerated and larger with right versus left KF, since the former occurred less frequently and thus less expectedly. Startle responses were associated with earlier and larger ECR responses (StartReact effect), with the largest effect again upon right KF. The results provide evidence that kinematic stimuli are able to elicit both startle reflexes and a StartReact effect, which depend on stimulus intensity and anticipation, as well as on the subjects' preparedness to respond.

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Section: Discussionmentioning

confidence: 99%

Evidence for Startle Effects due to Externally Induced Lower Limb Movements: Implications in Neurorehabilitation

Castellote

Kofler²,

Mayr³

et al. 2017

BioMed Research International

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“…One g oal of our experimental design was to minimize or eliminate the engagement of voluntary responses to mechanical perturbation in the learning process so that we could attribute any observed learning directly to the neural mechanisms that generate feedback responses rather than learning from whatever mechanisms generate voluntary motor commands. We did this by using very short duration perturbations (20 ms) and instructing participants to not intervene with the perturbations, both of which have been previously shown elicit long-latency stretch reflexes (50-100 ms post-pert urbation) while reducing or eliminating associated voluntary responses (>100 ms post-perturbation) (Asatryan and Feldman, 1965;Crago et al, 1976;Ghez and Shinoda, 1978;Lee and Tatton, 1982;Calancie and Bawa, 1985;Lewis et al, 2005;Pruszynski et al, 2008;Schuurmans et al, 2009;Shemmell et al, 2009;Kurtzer et al, 2010;Forgaard et al, 2015Forgaard et al, , 2016Forgaard et al, , 2019Kurtzer, 2019) . Our paradigm did create the expected response profiles such as no reliable decrease in muscle activity after 100 ms post-perturbation with shoulder fixation, presumably because the evoked response in the voluntary epoch was minimal to begin with (Figure 4 A-B).…”

Section: Limitationsmentioning

confidence: 99%

“…First, we used mechanical perturbations with very short durations (20 ms) previously shown to elicit reflex responses but very weak or non-existent voluntary muscle responses (Ghez and Shinoda, 1978;Lee and Tatton, 1982;Lewis et al, 2005;Schuurmans et al, 2009;Kurtzer et al, 2010;Kurtzer, 2019) . Second, we instructed participants to not intervene with the mechanical perturbations previously shown to substantially reduce or eliminate voluntary muscle responses (Asatryan and Feldman, 1965;Crago et al, 1976;Calancie and Bawa, 1985;Shemmell et al, 2009;Forgaard et al, 2015Forgaard et al, , 2016Forgaard et al, , 2019 .…”

Section: Introductionmentioning

confidence: 99%

Motor learning and transfer: from feedback to feedforward control

Maeda

Gribble

Pruszynski

2019

Preprint

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Previous work has demonstrated that when learning a new motor task, the nervous system modifies feedforward (ie. voluntary) motor commands and that such learning transfers to fast feedback (ie. reflex) responses evoked by mechanical perturbations. Here we show the inverse, that learning new feedback responses transfers to feedforward motor commands. Sixty human participants (34 females) used a robotic exoskeleton and either 1) received short duration mechanical perturbations (20 ms) that created pure elbow rotation or 2) generated self-initiated pure elbow rotations . They did so with the shoulder joint free to rotate (normal arm dynamics) or locked (altered arm dynamics) by the robotic manipulandum. With the sho ulder unlocked, the perturbation evoked clear shoulder muscle activity in the long-latency stretch reflex epoch (50-100ms post-perturbation), as required for countering the imposed joint torques, but little muscle activity thereafter in the so-called voluntary response. After locking the shoulder joint, which alters the required joint torques to counter pure elbow rotation, we found a reliable reduction in the long-latency stretch reflex over many trials. This reduction transferred to feedforward control as we observed 1) a reduction in shoulder muscle activity during self-initiated pure elbow rotation trials and 2) kinematic errors (ie. aftereffects) in the direction predicted when failing to compensate for normal arm dynamics, even though participants never practiced self-initiated movements with the shoulder locked. Taken together, our work shows that transfer between feedforward and feedback control is bidirectional, furthering the notion that these processes share common neural circuits that underlie motor learning and transfer .

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“…In a manner similar to previous studies Ravichandran et al, 2013;Forgaard et al, 2016) (Ravichandran et al, 2013;Forgaard et al, 2015). Integrated values for each epoch were taken from the rectified EMG traces on a trial-by-trial basis.…”

Section: Data Collection and Analysismentioning

confidence: 99%

“…Among many notable examples, the magnitude of the LLR scales based on target location , is sensitive to limb mechanics , and as traditionally investigated, the instruction of how to respond to a perturbation (Hammond, 1956) The issue of whether volitional characteristics of the LLR are produced through feedback gain changes in presumably supraspinal circuitry (Lee and Tatton, 1975;Pruszynski et al, 2014), or the appearance of a flexible feedback response only arises because a voluntary response is triggered early by the perturbation and superimposes onto the LLR (Rothwell et al, 1980;Manning et al, 2012) has been investigated for many years. Recent studies have consistently shown that LLR modulation begins at a shorter latency than the earliest possible voluntary response Forgaard et al, 2015). Despite this, many groups have shown that the magnitude of the LLR remains strongly related to volitional activity (Rothwell et al, 1980;Pruszynski et al, 2008;Manning et al, 2012;Crevecoeur et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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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Voluntary reaction time and long-latency reflex modulation

Cited by 25 publications

References 46 publications

Evidence for Startle Effects due to Externally Induced Lower Limb Movements: Implications in Neurorehabilitation

Evidence for Startle Effects due to Externally Induced Lower Limb Movements: Implications in Neurorehabilitation

Motor learning and transfer: from feedback to feedforward control

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

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