Dimensionality of joint torques and muscle patterns for reaching

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Motor behaviors are generated by basic muscle activation patterns, implying a modular organization by the central nervous system (CNS).
• The relationship between muscle pattern dimensionality and joint torque dimensionality is complex due to system redundancy and non-linearity.

Purpose of the Study:

• To investigate the dimensionality of muscle patterns and joint torques during arm reaching movements.
• To compare the spatial, temporal, and spatiotemporal organization of muscle activity and joint torques.

Main Methods:

• Multidimensional decomposition techniques were used to estimate dimensionality.
• Torques and muscle patterns during fast reaching movements in multiple directions were analyzed.

Main Results:

• Torque organization was captured by 2-3 spatial generators and a single temporal generator.
• Muscle pattern dimensionality was higher than torque dimensionality.
• Muscle patterns exhibited asynchronous coordination, unlike the synchronous torque patterns.

Conclusions:

• Higher muscle pattern dimensionality may be necessary for the CNS to manage musculoskeletal non-linearities.
• A limited number of building blocks are used to generate flexible endpoint trajectories with simple kinematic features.