title: Body sway adaptation to addition but not withdrawal of stabilizing visual information is delayed by a concurrent cognitive task.
abstract: The aim of this study was to test the effects of a concurrent cognitive task on the promptness of the sensorimotor integration and reweighting processes following addition and withdrawal of vision. Fourteen subjects stood in tandem while vision was passively added and removed. Subjects performed a cognitive task, consisting of counting backward in steps of three, or were "mentally idle." We estimated the time intervals following addition and withdrawal of vision at which body sway began to change. We also estimated the time constant of the exponential change in body oscillation until the new level of sway was reached, consistent with the current visual state. Under the mentally idle condition, mean latency was 0.67 and 0.46 s and the mean time constant was 1.27 and 0.59 s for vision addition and withdrawal, respectively. Following addition of vision, counting backward delayed the latency by about 300 ms, without affecting the time constant. Following withdrawal, counting backward had no significant effect on either latency or time constant. The extension by counting backward of the time interval to stabilization onset on addition of vision suggests a competition for allocation of cortical resources. Conversely, the absence of cognitive task effect on the rapid onset of destabilization on vision withdrawal, and on the relevant reweighting time course, advocates the intervention of a subcortical process. Diverting attention from a challenging standing task discloses a cortical supervision on the process of sensorimotor integration of new balance-stabilizing information. A subcortical process would instead organize the response to removal of the stabilizing sensory input.NEW & NOTEWORTHYThis study is the first to test the effect of an arithmetic task on the time course of balance readjustment following visual withdrawal or addition. Performing such a cognitive task increases the time delay following addition of vision but has no effect on withdrawal dynamics. This suggests that sensorimotor integration following addition of a stabilizing signal is performed at a cortical level, whereas the response to its withdrawal is "automatic" and accomplished at a subcortical level.
authors.affiliation: Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Pavia, Italy; and jeanlouis.honeine@unipv.it.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Honeine
authors.affiliation: Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Pavia, Italy; and.
authors.forename: Oscar
authors.initials: O
authors.lastname: Crisafulli
authors.affiliation: Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Pavia, Italy; and.|Centro Studi Attività Motorie (CSAM), Fondazione Salvatore Maugeri (IRCSS), Scientific Institute of Pavia, Pavia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Schieppati
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000704:Analysis of Variance; D001683:Biological Clocks / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D055815:Young Adult
keywords: balance; cognitive task; processing time; sensorimotor integration; sensory reweighting; vision