Stimulus-Locked Responses on Human Upper Limb Muscles and Corrective Reaches Are Preferentially Evoked by Low Spatial Frequencies

Abstract

In situations requiring immediate action, humans can generate visually-guided responses at remarkably short latencies. Here, to better understand the visual attributes that best evoke such rapid responses, we recorded upper limb muscle activity while participants performed visually-guided reaches towards Gabor patches composed of differing spatial frequencies (SFs). We studied reaches initiated from a stable posture (experiment 1, a static condition), or during on-line reach corrections to an abruptly displaced target (experiment 2, a dynamic condition). In both experiments, we detail the latency and prevalence of stimulus-locked responses (SLRs), which are brief bursts of EMG activity that are time-locked to target presentation rather than movement onset. SLRs represent the first wave of EMG recruitment influenced by target presentation, and enable quantification of rapid visuomotor transformations. In both experiments, reach targets composed of low SFs elicited the shortest latency and most prevalent SLRs, with SLR latency increasing and SLR prevalence decreasing for reach targets composed of progressively higher SFs. SLRs could be evoked in either the static or dynamic condition, and when present in experiment 2, were associated with shorter latency and larger magnitude corrections. The results in experiment 2 are consistent with a linkage between the forces produced by SLRs and the earliest portion of on-line reach corrections. Overall, our results demonstrate that stimuli composed of low SFs preferentially evoke the most rapid visuomotor responses that, in the context of rapidly correcting an on-going reaching movement, are associated with earlier and larger on-line reach corrections.

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

“…Despite such large variability, the SLR magnitudes reported here are significantly larger than any reported previously (Pruszynski et al, 2010;Gu et al, 2016;Kozak et al, 2019).…”

“…In contrast, visual responses latencies in the superior colliculus (SC; from which the tecto-reticulo-spinal track originates) precede the SLR (Stuphorn et al, 1999;Rezvani and Corneil, 2008), which makes the SC a potential candidate for mediating the SLR. Further, high contrast (Li and Basso, 2008;Marino et al, 2012;Wood et al, 2015) or low spatial frequency (Chen et al, 2018;Kozak et al, 2019) targets elicit larger-magnitude and shorter-latency visual . CC-BY-NC-ND 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.…”

“…We have previously reported that SLRs may differ in magnitude (Gu et al, 2016) and/or latency (Kozak et al, 2019) depending on task context and stimulus properties, respectively. We examined the data from experiment 1 to investigate the effect of target speed on SLR latency and magnitude.…”

“…However, if the ball is thrown to us, time is of the essence and we must perform a rapid reach in order to catch the ball. In such situations, the latency of the response depends on the visual attributes of the stimulus; for example, earlier responses are elicited by larger or higher contrast targets, or stimuli defined by lower spatial frequencies (Veerman et al, 2008;Wood et al, 2015;Kozak et al, 2019). Other work has suggested that the most rapid visuomotor transformation for reaching is mediated by a tecto-reticulo-spinal pathway, which lies in parallel to the well-studied corticospinal pathway (Day and Lyon, 2000;Pruszynski et al, 2010;Gu et al, 2016;Glover and Baker, 2019).…”

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

“…This experiment was designed to investigate the influence of cognitive expectations on express visuomotor responses. The participants were instructed to reach as fast as possible toward a visual target that appeared as a brief flash of a complete circle, features that facilitate SLRs (Contemori et al 2020; Kozak et al 2019). The target location was unpredictable or partially predictable from the orientation of a symbolic arrow-shaped cue (Figure 1).…”