Abstract

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 rapid reaching? High-contrast, fast-moving targets elicit strong responses in the superior colliculus (SC), a structure associated with express saccades and implicated in rapid electromyographic (EMG) responses on upper limb muscles. To test the influence of stimulus properties on rapid reaches, 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 that has recently been shown to robustly elicit fast visuomotor responses. Our analysis focused on stimulus-locked responses (SLRs) on upper limb muscles. SLRs appear within <100 ms of target presentation, and as the first wave of muscle recruitment they have been hypothesized to arise from the SC. Across 32 subjects studied in both experiments, 97% expressed SLRs in the emerging target paradigm, whereas only 69% expressed SLRs in an immediate response paradigm toward static targets. Faster-moving targets (experiment 1) evoked large-magnitude SLRs, whereas high-contrast fast-moving targets (experiment 2) evoked short-latency, large-magnitude SLRs. In some instances, SLR magnitude exceeded the magnitude of movement-aligned activity. Both large-magnitude and short-latency SLRs were correlated with short-latency reach reaction times. Our results support the hypothesis that, in scenarios requiring expedited responses, a subcortical pathway originating in the SC elicits the earliest wave of muscle recruitment, expediting reaction times.NEW & NOTEWORTHY How does the brain rapidly transform vision into action? Here, by recording upper limb muscle activity, we find that high-contrast and fast-moving targets are highly effective at evoking rapid visually guided reaches. We surmise that a brain stem circuit originating in the superior colliculus contributes to the most rapid reaching responses. When time is of the essence, cortical areas may serve to prime this circuit and elaborate subsequent phases of recruitment.

Highlights

  • To perform a visually guided reach, for example to pick up a baseball, visual information such as the shape and size of the ball is transformed into motor commands that are communicated to the motor periphery

  • Previous work has shown that the emerging target paradigm is highly effective at eliciting rapid visuomotor responses, such as stimulus-locked responses (SLRs) and short-latency reach reaction times (RTs) [8, 19]

  • When examining how the SLR relates to RT, we found a positive correlation between latency and RT in both experiments; shorter-latency SLRs were correlated with more rapid RTs

Read more

Summary

Introduction

To perform a visually guided reach, for example to pick up a baseball, visual information such as the shape and size of the ball is transformed into motor commands that are communicated to the motor periphery. If the ball is thrown to us, time is of the essence and we must perform a rapid reach 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-size, higher-contrast, or lower-spatial frequency targets [1,2,3]. To better understand the most rapid visuomotor transformations for limb control, we and others have recorded electromyographic (EMG) activity from upper limb muscles during rapid visually guided reaches. Doing so has led to the identification of stimulus-locked responses (SLRs) that are the first wave of muscle activity influenced by the visual stimulus [SLRs are termed rapid visuomotor responses

Objectives
Methods
Results
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call