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. This 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.

Effect of a Concurrent Cognitive Task, with Stabilizing Visual Information and Withdrawal, on Body Sway Adaptation of Parkinsonian’s Patients in an Off-Medication State: A Controlled Study

“…The positions of the center of pressure (COP) in the mediolateral (ML) and anteroposterior (AP) directions were computed offline using a custom-made MATLAB (MathWorks, Natick, MA, USA) routine and were bandpass filtered between 0.1 and 5 Hz [ 27 ] with a no-lag 2nd order Butterworth filter. The COP trajectories were computed for each of the three trials and then averaged.…”

Postural Control in Bilateral Vestibular Failure: Its Relation to Visual, Proprioceptive, Vestibular, and Cognitive Input

“…Our primary aim was to compare postural control in BVF and healthy control (HC) subjects by systematically modulating visual, SSC, otolith, and proprioceptive input. As postural control might be influenced by focused attention and/or cognitive distraction [dual task ( 29 )] and more challenging balance tasks (tandem stance), we added these conditions to elaborate how these factors might unmask latent postural instability in BVF.…”

Balance in Blind Subjects: Cane and Fingertip Touch Induce Similar Extent and Promptness of Stance Stabilization

“…Of course, a sizeable difference in latency was observed, as expected, between addition and subtraction of the sensory input. The origin of this difference has been discussed at length in previous papers ( Sozzi et al, 2011 , 2012 ; Schieppati et al, 2014 ; Honeine et al, 2017 ). We found here that there was no significant interaction between cane and finger or addition and withdrawal of the haptic stimulus.…”

“…This would imply that lowering (or raising) of the cane by a complex coordinate movement entailing a postural adjustment (although minor, given the light weight of the cane) does not produce a longer latency than the simple lowering (or raising) of the index finger. Since the instruction was to exert a very low force level during the task, we were expecting a stronger control during cane than finger lowering to the haptic surface, possibly accompanied a greater cognitive effort that would have delayed the integration process ( Honeine et al, 2017 ). Again, what matters seems to be the contact itself, producing the sensory haptic volley.…”

“…Do subjects with severe visual impairment have an edge by using the cane compared to using a finger? Or does appropriate cane use require a higher level of conscious control than the finger touching task ( Honeine et al, 2017 ) or larger anticipatory postural adjustments ( Chabran et al, 2001 ) that might attenuate the incoming input ( Starr and Cohen, 1985 ) and interfere with the promptness of stabilization?…”