Obstacle avoidance and a perturbation sensitivity model for motor planning

Area of Science:

• Neuroscience
• Biomechanics
• Human Motor Control

Background:

• Human reaching movements are complex, involving planning and execution.
• Previous studies suggested movement planning relies solely on visual space kinematics.
• The role of biomechanical factors in motor planning remained unclear.

Purpose of the Study:

• To investigate whether the central nervous system (CNS) plans human reaching movements based on visual space or incorporates biomechanical details.
• To determine if motor planning optimizes trajectory plans using specific details of the biomechanical system.
• To explore the influence of obstacle orientation on reaching movement trajectories.

Main Methods:

• Developed a novel obstacle avoidance paradigm for studying human reaching movements.
• Participants performed reaching tasks around a fixed-tip obstacle.
• Rotated the obstacle, start, and target locations to test for rotational symmetry in movement paths.

Main Results:

• Systematic variations in movement paths were observed despite rotationally symmetric visual task constraints.
• Observed path asymmetries suggest motor planning accounts for factors beyond visual space.
• Models incorporating anisotropic arm sensitivity or inertial properties best explained the observed trajectory variations.

Conclusions:

• Human arm movement planning is not solely based on visual space kinematics.
• The CNS incorporates biomechanical details, such as inertial properties, to optimize reaching trajectories and avoid obstacles.
• Motor control strategies are influenced by the physical characteristics of the musculoskeletal system.