title: Information and control strategy to solve the degrees-of-freedom problem for nested locomotion-to-reach.
abstract: Locomoting-to-reach to a target is a common visuomotor approach behavior that consists of two nested component actions: locomotion and reaching. The information and control strategies that guide locomotion and reaching in isolation are well studied, but their interaction during locomoting-to-reach behavior has received little attention. We investigated the role of proportional rate control in unifying these components into one action. Individuals use this control strategy with hand-centric disparity-based τ information to guide seated reaching (Anderson and Bingham in Exp Brain Res 205:291-306. doi: 10.1007/s00221-010-2361-9 , 2010) and use it with sequential information to perform targeted locomotion to bring an outstretched arm and hand to a target; first with eye-centric τ information and then hand-centric τ information near the target (Anderson and Bingham in Exp Brain Res 214:631-644. doi: 10.1007/s00221-011-2865-y , 2011). In the current study, participants performed two tasks: locomoting to bring a rigidly outstretched arm and hand to a target (handout), and locomoting to initiate and guide a reach to a target (locomoting-to-reach). Movement trajectories were analyzed. Results show that participants used proportional rate control throughout both tasks, in the sequential manner that was found by Anderson and Bingham (Exp Brain Res 214:631-644. doi: 10.1007/s00221-011-2865-y , 2011). Individual differences were found in the moment at which this information switch occurred in the locomoting-to-reach task. Some participants appeared to switch to proportional rate control with hand-τ once the hand came into view and others switched once the reaching component was complete and the arm was fully outstretched. In the locomoting-to-reach task, participants consistently initiated reaches when eye-τ specified a time-to-contact of 1.0 s. Proportional rate control provides a solution to the degrees-of-freedom problem in the classic manner, by making multiple things one.
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, 1101 E 10th St, Bloomington, IN, 47405, USA, ajfath@indiana.edu.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Fath
authors.forename: Brian S
authors.initials: BS
authors.lastname: Marks
authors.forename: Winona
authors.initials: W
authors.lastname: Snapp-Childs
authors.forename: Geoffrey P
authors.initials: GP
authors.lastname: Bingham
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology*; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009068:Movement / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult