title: A Trial-by-Trial Window into Sensorimotor Transformations in the Human Motor Periphery.
abstract: The appearance of a novel visual stimulus generates a rapid stimulus-locked response (SLR) in the motor periphery within 100 ms of stimulus onset. Here, we recorded SLRs from an upper limb muscle while humans reached toward (pro-reach) or away (anti-reach) from a visual stimulus. The SLR on anti-reaches encoded the location of the visual stimulus rather than the movement goal. Further, SLR magnitude was attenuated when subjects reached away from rather than toward the visual stimulus. Remarkably, SLR magnitudes also correlated with reaction times on both pro-reaches and anti-reaches, but did so in opposite ways: larger SLRs preceded shorter latency pro-reaches but longer latency anti-reaches. Although converging evidence suggests that the SLR is relayed via a tectoreticulospinal pathway, our results show that task-related signals modulate visual signals feeding into this pathway. The SLR therefore provides a trial-by-trial window into how visual information is integrated with cognitive control in humans.
  
  
  
  The presentation of a visual stimulus elicits a trial-by-trial stimulus-locked response (SLR) on the human limb within 100 ms. Here, we show that the SLR continues to reflect stimulus location even when subjects move in the opposite direction (an anti-reach). Remarkably, the attenuation of SLR magnitude reflected the cognitive control required to generate a correct anti-reach, with greater degrees of attenuation preceding shorter-latency anti-reaches and no attenuation preceding error trials. Our results are strikingly similar to neurophysiological recordings in the superior colliculus of nonhuman primates generating anti-saccades, implicating the tectoreticulospinal pathway. Measuring SLR magnitude therefore provides an unprecedented trial-by-trial opportunity to assess the influence of cognitive control on the initial processing of a visual stimulus in humans.
authors.affiliation: Department of Psychology and Brain and Mind Institute and.
authors.forename: Chao
authors.identifier: 0000-0002-9294-314X
authors.initials: C
authors.lastname: Gu
authors.affiliation: Department of Neurobiology, Northwestern University, Evanston, Illinois 60208.
authors.forename: Daniel K
authors.identifier: 0000-0002-3179-4072
authors.initials: DK
authors.lastname: Wood
authors.affiliation: Department of Psychology and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5B7, Brain and Mind Institute and.
authors.forename: Paul L
authors.identifier: 0000-0002-1368-032X
authors.initials: PL
authors.lastname: Gribble
authors.affiliation: Department of Psychology and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5B7, Brain and Mind Institute and Robarts Research Institute, University of Western Ontario, London, Ontario, Canada N6A 5B7, and bcorneil@uwo.ca.
authors.forename: Brian D
authors.identifier: 0000-0002-4702-7089
authors.initials: BD
authors.lastname: Corneil
mesh_terms: D000328:Adult; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D013647:Task Performance and Analysis; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: cognitive control; human; reaching; visual processing