Modulation of initial movement for double potential targets with specific time constraints

Ryoji Onagawa,Kazutoshi Kudo

doi:10.1038/s41598-021-01777-3

Abstract

In goal-directed behavior, individuals are often required to plan and execute a movement with multiple competing reach targets simultaneously. The time constraint assigned to the target is an important factor that affect the initial movement planning, but the adjustments made to the starting behavior considering the time constraints specific to each target have not yet been clarified. The current study examined how humans adjusted their motor planning for double potential targets with independent time constraints under a go-before-you-know situation. The results revealed that the initial movements were modulated depending on the time constraints for potential targets. However, under tight time constraints, the performance in the double-target condition was lower than the single-target condition, which was a control condition implemented to estimate performance when one target is ignored. These results indicate that the initial movement for multiple potential targets with independent time constraints can be modified, but the planning is suboptimal.

Highlights

In goal-directed behavior, individuals are often required to plan and execute a movement with multiple competing reach targets simultaneously
Several studies have investigated motor planning for multiple potential goals using the “Go-before-you-know paradigm,” in which a participant is required to launch a movement with multiple potential goals and the final goal is revealed after movement development1–10
In situations where the severities of the time constraints were comparable, the initial movement was directed toward the average direction of the potential targets, and in situations where there was a substantial difference in the severities of the time constraints, the initial movement was directed toward the target direction with a more severe time constraint

Summary

Introduction

In goal-directed behavior, individuals are often required to plan and execute a movement with multiple competing reach targets simultaneously. Based on this discrete view, several models have been created to solve the redundancy problem (for instance, when reaching for an object, there are numerous hand trajectories, joint movements, and muscle activation patterns that can be executed on a single target) To solve this problem, optimization based on various costs, such as jerks, torque-changes, variabilities of the final hand position, and effort have been proposed, and these perspectives have contributed greatly to our understanding of human motor control principles. Be selected when the advantage of the strategy disappears, such as when the distance between targets is large, when severe constraints on speed are imposed, or when the information on the targets is updated in s tages27 These findings suggest that the averaging behavior in motor planning in the presence of multiple goals may not exist as a control policy in itself, but is rather a behavior that reflects optimization for task accomplishment

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