Anticipatory action planning for stepping onto competing potential targets

Abstract

The brain plans an anticipatory action for performing tasks successfully and effortlessly even if there are multiple possible options. There is increasing evidence that, when multiple actions are possible, the brain considers two factors when planning an anticipatory action—the probabilistic value and the action cost for each potential action. When the action involves maintaining upright balance, such as standing, stepping, or walking, the action cost for maintaining postural stability could be considered dominantly. We addressed this issue by using a “go-before-you-know” task to step onto a target on the floor. In this task, two potential targets were located on the medial or lateral side of the stepping foot, and the true target was cued only after participants shifted their loads to leave that foot. Participants initiated their stepping actions without knowing which of the potential targets would be the true one. The results showed that, for the majority of participants, lateral displacements of the center of pressure (COP) with two potential targets were similar to those when a single target exists on the individual’s medial side. Given that mediolateral postural stability became more destabilized with stepping onto the medial target than stepping onto the lateral target, they were likely to plan their mediolateral components of the postural adjustments for the worst-case scenario (i.e., falling). Additionally, posterior COP movements with two potential targets became smaller than those with a single target, suggesting an effort to create extra time to determine the true target and to adjust the swing foot. Based on these findings, we concluded that action costs for maintaining postural stability were considered dominantly for planning an anticipatory action to accomplish a stepping task successfully while ensuring upright balance.

Optical mapping of ground reaction force dynamics in freely behavingDrosophila melanogasterlarvae

“…The fact that this redistribution occurs hundreds of milliseconds before the start of a head sweep suggests that it may be part of an active preparatory behaviour, as opposed to a biomechanical consequence of the behaviour itself. Similar types of preparatory behaviours involving redistribution of body mass have been observed in caterpillars before cantilevering behaviours (Lin et al, 2011), adult flies during fast escape behaviours (Card & Dickinson, 2008) and humans during stepping (Watanabe & Higuchi, 2022). In addition to redistributing body mass to regions in between protopodia, we also observed unexpected tripod-shaped transient substrate interactions in posterior terminal regions of larvae immediately before forward waves and headsweeps.…”

“…This redistribution occurs hundreds of milliseconds before the start of a head sweep, suggesting that it may be part of an active preparatory behaviour. Similar preparatory behaviours have been observed in caterpillars before cantilevering behaviours (Lin et al, 2011), adult flies during fast escape behaviours (Card & Dickinson, 2008) and humans during stepping (Watanabe & Higuchi, 2022).…”

Optical mapping of ground reaction force dynamics in freely behaving Drosophila melanogaster larvae

“…This redistribution occurs hundreds of milliseconds before the start of a headsweep, suggesting that it may be part of an active preparatory behaviour. Similar preparatory behaviours have been observed in caterpillars before cantilevering behaviours ( Lin et al, 2011 ), adult flies during fast escape behaviours ( Card and Dickinson, 2008 ), and humans during stepping ( Watanabe and Higuchi, 2022 ). More detailed characterisation of this behaviour remains a challenge owing to the changing position of the mouth hooks.…”

Instability during Stepping and Distance between the Center of Mass and the Minimal Moment Axis: Effect of Age and Speed

“…It is noteworthy that these age-related changes were more pronounced in the sagittal plane. Furthermore, although both age groups increased angular momentum with increasing speed during stepping, the age-related changes previously observed at spontaneous speed were exacerbated at faster speeds [21]. Taken together, these results suggest that the greater variation in angular momentum with age and speed generates larger values of angular momentum derivatives and consequently contributes to increasing the distance between the COM and the MMA.…”

“…In this context, some authors recently studied instability during stepping. Using the COP trajectory, Watanabe and Higuchi [21] demonstrated that action costs for maintaining postural stability are considered dominantly for planning the stepping. The margin of stability [22] was also analyzed during stepping in different situations, and the higher risk of falls in frail individuals such as older adults were highlighted.…”