Postural responses to target jumps and background motion in a fast pointing task

Abstract

When reaching towards an object while standing, one’s hand responds very quickly to visual perturbations such as the target being displaced or the background moving. Such responses require postural adjustments. When the background moves, its motion might be attributed to self-motion in a stable world, and thereby induce compensatory postural adjustments that affect the hand. The changes in posture associated with a given hand movement response may, therefore, be different for the two types of perturbations. To see whether they are, we asked standing participants to move their hand in the sagittal direction away from their body to targets displayed on a horizontal screen in front of them. The target displacements and background motion were in the lateral direction. We found hand movement responses that were in line with earlier reports, with a latency that was slightly shorter for target displacements than for background motion, and that was independent of target displacement size or background motion speed. The trunk responded to both perturbations with a modest lateral sway. The two main findings were that the upper trunk responded even before the hand did so and that the head responded to background motion but hardly responded to target displacements. These findings suggest that postural adjustments associated with adjusting the hand movement precede the actual adjustments to the movement of the hand, while at the same time, participants try to keep their head stable on the basis of visual information.

A simple interception task used as diagnostic tool of multisensory integration problems in aging

“…The larger screen allowed us to reduce the setup's visual difficulty and the higher background velocity allowed us to increase the multisensory integration demand on participants to potentially increase the differences between the two groups of participants (OA and YA). As hypothesized, and in accordance with results reported in the literature (Saijo et al, 2005;Zhang et al, 2018), the faster background induced a larger illusion effect in YA as compared to the original experiment (Chapter 3) in the baseline and counting conditions (no significant difference in the illusion effect of YA was found for the balance condition between the two experiments, but the trend was in the expected direction). Besides the main difference of the faster background speed (24 cm/s instead of 12 cm/s), other setup differences might have played a role in the increased illusion effect as well.…”

“…The larger screen allowed us to reduce the setup's visual difficulty and the higher background velocity allowed us to increase the multisensory integration demand on participants. We hypothesized that a higher background velocity will increase the illusion effect for YA as compared to the results presented in Chapter 3 (H1), as seen earlier in the literature (Saijo et al, 2005;Zhang et al, 2018). Second, we expect this faster background to increase the differences in results between OA and YA (H2) and show the three different effects of the illusion in OA (normal, reverse and no effect) as seen in the previous chapters (H3).…”

“…In order to increase the effect of the illusion, and therewith possibly its sensitivity to distinguish between individuals and conditions, we used a higher velocity of the background. Previous results showed that a faster background increased the illusion effect caused by this background when intercepting targets on horizontal screens (Saijo et al, 2005;Zhang et al, 2018). Saijo et al (2005) investigated the differences between two background velocities, 7 and 70 cm/s.…”

“…Saijo et al (2005) investigated the differences between two background velocities, 7 and 70 cm/s. Zhang et al (2018) investigated the differences between two background velocities as well, 20 and 60 cm/s. The larger illusion caused by the faster background may be explained by a relatively larger target-background movement difference.…”

Highs and Lows in Motor Control Development

“…However, because residual errors remain in the motor program or because the object properties might change unexpectedly, feedback processing comes into play to correct online actions and reach the desired goal (Buckingham, Ranger, & Goodale, 2011). Such movement preparation and execution imply multisensory integration of both visual and proprioceptive information from the body and the environment (Sober & Sabes, 2003;Zhang, Brenner, Duysens, Verschueren, & Smeets, 2018). Through the emergence of internal models, the last decades have seen the refinement of the concept of online control that is better described as a comparison between a predicted feedback built from a forward model and the proper sensory feedback processing (see Desmurget & Grafton, 2000 for a review).…”