An Emerging Target Paradigm to Evoke Fast Visuomotor Responses on Human Upper Limb Muscles

Kozak, Rebecca A.; Cecala, Aaron L.

doi:10.3791/61428

Cited by 21 publications

(83 citation statements)

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“…One objective of the current study was to identify experimental conditions that can generate robust SLRs in most subjects. Notably, Kozak et al (2020) detected SLRs in all five of the participants that they tested, by adopting a moving target paradigm involving a visual barrier to partially occlude the target trajectory of motion. Here, we observed +SLRs among all but one of the 21 unique subjects tested with different versions of the moving target paradigm.…”

Section: Discussionmentioning

confidence: 99%

“…Our experimental setup had some key differences from that adopted by Kozak et al (2020). In that study, the authors presented the paradigm via a horizontal mirror that reflected a down-facing monitor, which also projected a real-time cursor to provide the participants with the visual feedback of the hand location.…”

Section: Discussionmentioning

confidence: 99%

“…Pruszynski et al (2010) failed to detect SLRs from surface EMG recordings and detected positive SLRs in only 7 out of 16 participants (∼44% prevalence rate) using intramuscular electrodes. Recently, Kozak et al (2020) obtained a 100% SLR detection rate among a sample of five individuals by adopting an emerging target paradigm , which was motivated by earlier oculomotor studies (for review see Fiehler et al 2019). This suggests that the circuit responsible for SLRs can be biased according to task conditions.…”

Section: Introductionmentioning

confidence: 99%

“…In the emerging target paradigm, the stimulus initially fell toward a visual barrier and re-emerged beneath it at a time that was specified by the target velocity. This made the target presentation time predictable via extrapolation of the target trajectory behind the barrier (Kozak et al 2020). Previous studies showed that the collicular response to visual stimuli is more vigorous with moving than static stimuli (Schneider and Kastner 2005; Lau et al 2011), raising the possibility that target motion facilitates SLRs because it provides a higher sensory salience in the superior colliculus itself.…”

Section: Introductionmentioning

confidence: 99%

“…In experiment 1, we used a constant velocity moving target paradigm, akin to that used by Kozak et al (2020), thus making the stimulus onset time predictable via an antiderivative computation of its velocity (Senot et al 2003; Zago et al 2009; Fiehler et al 2019), and a consequent extrapolation for a physically plausible target trajectory. In the second experiment, we kept the target onset time constant but varied the location at which it emerged beneath the barrier.…”

Section: Introductionmentioning

confidence: 99%

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The influence of temporal predictability on express visuomotor responses

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Loeb

Wallis

et al. 2020

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Volitional visuomotor responses in humans are generally thought to manifest 100ms or more after stimulus onset. Under appropriate conditions, however, much faster target-directed responses can be produced at upper limb and neck muscles. These “express” responses have been termed stimulus-locked responses (SLRs) and are proposed to be modulated by visuomotor transformations performed subcortically via the superior colliculus. Unfortunately, for those interested in studying SLRs, these responses have proven difficult to detect consistently across individuals. The recent report of an effective paradigm for generating SLRs in 100% of participants appears to change this. The task required the interception of a moving target that emerged from behind a barrier at a time consistent with the target velocity. Here we aimed to reproduce the efficacy of this paradigm for eliciting SLRs and to test the hypothesis that its effectiveness derives from the predictability of target onset time as opposed to target motion per se. In one experiment, we recorded surface EMG from shoulder muscles as participants made reaches to intercept temporally predictable or unpredictable targets. Consistent with our hypothesis, predictably timed targets produced more frequent and stronger SLRs than unpredictably timed targets. In a second experiment, we compared different temporally predictable stimuli and observed that transiently presented targets produced larger and earlier SLRs than sustained moving targets. Our results suggest that target motion is not critical for facilitating the expression of an SLR and that timing predictability does not rely on extrapolation of a physically plausible motion trajectory. These findings provide support for a mechanism whereby an internal timer, probably located in cerebral cortex, primes the processing of both visual input and motor output within the superior colliculus to produce SLRs.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The influence of temporal predictability on express visuomotor responses

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Loeb

Wallis

et al. 2020

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High contrast, moving targets in an emerging target paradigm promote fast visuomotor responses during visually guided reaching

Kozak,

Corneil

2021

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Humans have a remarkable capacity to rapidly interact with the surrounding environment, often by transforming visual input into motor output on a moment-to-moment basis. But what visual features promote the shortest-latency reach responses? To address this question, we had human subjects perform visually guided reaches to moving targets varied by speed (experiment 1), or speed and contrast (experiment 2) in an emerging target paradigm, which has recently been shown to robustly elicit fast visuomotor responses. Our analysis focused on stimulus-locked responses (SLRs) on upper limb muscles. SLRs represent the first wave of muscle recruitment tied to visual target onset, appearing within <100 ms. Across 32 subjects studied in both experiments, 97% expressed SLRs in the emerging target paradigm. In comparison, 69% of these subjects expressed SLRs in a visually-guided reach paradigm. Within the emerging target paradigm, we found that target speed impacted SLR magnitude, whereas target contrast impacted SLR latency and magnitude. Thus, high contrast, faster-moving targets in the emerging target paradigm robustly recruited the circuitry mediating the most rapid visuomotor transformations for reaching, and such responses were associated with shorter latency RTs. Our results support the hypothesis that a subcortical pathway originating in the superior colliculus may be involved in the earliest wave of muscle recruitment following visual stimulus presentation. In scenarios requiring expedited responses, cortical areas may serve to prime this subcortical pathway, and elaborate subsequent phases of muscle recruitment following the SLR.Significance StatementHumans have a remarkable capacity, when necessary, to rapidly transform vision into action. But how does the brain do this? Here, by studying human subjects reaching to suddenly-appearing targets, we find that the earliest visually-guided actions are produced in response to high-contrast, moving targets. A millisecond-resolution examination of upper limb muscle recruitment shows that motor output can begin within less than 100 ms of target presentation. We surmise that this earliest recruitment arises from a phylogenetically-conserved brainstem circuit originating in the superior colliculus. Rather than being directly involved in the earliest phase of visuomotor actions, cortical areas may prime this brainstem circuit to produce initial muscle recruitment, and then elaborate subsequent phases of recruitment when time is of the essence.

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Trial-by-trial modulation of express visuomotor responses induced by symbolic or barely detectable cues

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Loeb

Wallis

et al. 2021

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Human cerebral cortex can produce visuomotor responses that are modulated by contextual and task-specific constraints. However, the distributed cortical network for visuomotor transformations limits the minimal response time of that pathway. Notably, humans can generate express visuomotor responses that are inflexibly tuned to the target location and occur 80-120ms from stimulus presentation (stimulus-locked responses, SLRs). This suggests a subcortical pathway for visuomotor transformations involving the superior colliculus and its downstream reticulo-spinal projections. Here we investigated whether cognitive expectations can modulate the SLR. In one experiment, we recorded surface EMG from shoulder muscles as participants reached toward a visual target whose location was unpredictable in control conditions, and partially predictable in cue conditions by extrapolating a symbolic cue (75% validity). Valid symbolic cues led to faster and larger SLRs than control conditions; invalid symbolic cues produced slower and smaller SLRs than control conditions. This is consistent with a cortical top-down modulation of the putative subcortical SLR-network. In a second experiment, we presented high-contrast targets in isolation (control) or ~24ms after low-contrast stimuli, which could appear at the same (valid cue) or opposite (invalid cue) location as the target, and with equal probability (50% cue validity). We observed faster SLRs than control with the valid low-contrast cues, whereas the invalid cues led to the opposite results. These findings may reflect exogenous priming mechanisms of the SLR network, potentially evolving subcortically via the superior colliculus. Overall, our results support both top-down and bottom-up modulations of the putative subcortical SLR network in humans.NEW & NOTEWORTHYExpress visuomotor responses in humans appear to reflect subcortical sensorimotor transformation of visual inputs, potentially conveyed via the tecto-reticulo-spinal pathway. Here we show that the express responses are influenced both by symbolic and barely detectable spatial cues about stimulus location. The symbolic cue-induced effects suggest cortical top-down modulation of the putative subcortical visuomotor network. The effects of barely detectable cues may reflect exogenous priming mechanisms of the tecto-reticulo-spinal pathway.

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An Emerging Target Paradigm to Evoke Fast Visuomotor Responses on Human Upper Limb Muscles

Abstract: We present a new behavioual paradigm that elicits robust fast visuomotor responses on human upper limb muscles during visually guided reaches.

Cited by 21 publications

References 4 publications

The influence of temporal predictability on express visuomotor responses

The influence of temporal predictability on express visuomotor responses

High contrast, moving targets in an emerging target paradigm promote fast visuomotor responses during visually guided reaching

Trial-by-trial modulation of express visuomotor responses induced by symbolic or barely detectable cues

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