How a lateralized brain supports symmetrical bimanual tasks

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Bimanual object manipulation requires precise coordination of opposing forces.
• Understanding how the lateralized brain manages this bimanual coordination is crucial.

Purpose of the Study:

• To investigate how the brain assigns roles to each hand during coordinated bimanual tasks.
• To determine the factors influencing the choice of the dominant hand.

Main Methods:

• Functional magnetic resonance imaging (fMRI) to observe brain activity.
• Electromyography (EMG) and transcranial magnetic brain stimulation (TMS) for neurophysiological analysis.
• Behavioral experiments involving tool manipulation to control a cursor.

Main Results:

• The brain flexibly assigns one hand as the prime actor, with the other assisting.
• Hand assignment shifts based on the directional relationship between hand forces and cursor movement.
• This flexible role assignment is reflected in midline shifts of activity in motor control areas and muscles.

Conclusions:

• The dominant hand in bimanual tasks is determined by spatial dynamics, not fixed handedness.
• The motor system exhibits flexible role assignment at multiple levels, from cortical areas to individual muscles.