Finger interaction during maximal radial and ulnar deviation efforts: experimental data and linear neural network...

Area of Science:

• Neuroscience
• Biomechanics
• Human Motor Control

Background:

• Understanding finger interactions is crucial for grasping and manipulation.
• Previous research has focused primarily on flexion movements, with less attention to lateral (radial/ulnar) deviation.
• The neural mechanisms governing coordinated finger movements remain incompletely understood.

Purpose of the Study:

• To characterize finger force interactions during radial/ulnar deviation, including combined flexion.
• To investigate the phenomena of force enslaving, deficit, and facilitation.
• To explore the neural versus biomechanical origins of these finger interactions.

Main Methods:

• Subjects performed single-finger and multi-finger maximal voluntary contractions (MVCs) in various directions.
• Maximal forces and interaction indices between fingers were quantified.
• A linear neural network model was employed to analyze motor command inputs and finger force outputs.

Main Results:

• Maximal voluntary contractions for radial/ulnar deviation were weaker than for flexion.
• Observed force 'enslaving' (force production in non-instructed fingers) and force 'deficit' (reduced MVC in multi-finger tasks).
• Identified 'preferred direction enslaving' and 'negative deficit' (force facilitation), suggesting neural origins for these phenomena.

Conclusions:

• Finger force control during lateral deviation is influenced by neural factors, as evidenced by preferred direction enslaving.
• Extensive neural interconnections among hand muscles contribute to force facilitation and complex movement patterns.
• A linear neural network model accurately predicts finger forces, aiding in understanding peripheral constraints during prehension.