Altered Arm-Body Coordination with Triggered Pointing Responses as Influenced by Task Predictability.

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Reaching movements generate reaction forces impacting postural stability.
• Anticipatory postural adjustments are essential for maintaining balance during voluntary movements.
• The role of target-shift predictability in early postural activity during double-step pointing remains unclear.

Purpose of the Study:

• To investigate the coordination between arm and body motion during double-step pointing movements.
• To determine if early postural activity depends on target-shift predictability.
• To compare the coordination of arm and body motion in response to predictable versus unpredictable target shifts.

Main Methods:

• Participants performed double-step pointing movements while standing.
• Target-shift predictability was manipulated by varying the certainty of the target's direction.
• Kinematic data of arm and body movements were recorded and analyzed.

Main Results:

• A target jump evoked an adjustment in the arm followed by the body, opposing the initial pointing response.
• The arm-then-body response sequence was consistent regardless of target-shift predictability.
• Predictable target-shift directions led to closer timing between arm and body onsets.

Conclusions:

• The coordination of triggered postural corrections is influenced by response predictability.
• Altered coordination in triggered reactions suggests a dependence on predictability for body movement control.
• This study reveals insights into the predictive control mechanisms governing arm and body synergy during perturbed movements.