Throwing while looking through prisms. II. Specificity and storage of multiple gaze-throw calibrations

Area of Science:

• Motor control
• Human adaptation
• Visual-motor integration

Background:

• Prism adaptation studies investigate how the brain recalibrates motor commands in response to altered sensory input.
• Understanding short-term and long-term motor learning is crucial for rehabilitation and understanding sensorimotor plasticity.

Purpose of the Study:

• To investigate short-term and long-term motor adaptation to prism-induced visual displacement during a throwing task.
• To determine the specificity of motor learning to body parts and movement types.
• To assess the retention of learned motor recalibrations.

Main Methods:

• Human subjects performed clay ball throws at a visual target while wearing wedge prism spectacles.
• Short-term adaptation was studied by observing changes in throw accuracy and gaze-throw angle over trials.
• Long-term adaptation involved alternating throws with and without prisms over six weeks, followed by retention tests.

Main Results:

• Subjects initially missed targets due to prism-induced gaze deviation but adapted within 10-30 throws.
• A negative aftereffect was observed upon prism removal, requiring further throws to re-adapt.
• Adaptation was specific to the trained hand and throw type (overhand vs. underhand).
• Long-term adaptation allowed subjects to hit targets on the first throw, with and without prisms.
• Learned calibrations persisted for over 27 months and involved coordinated adjustments in eye, head, and trunk angles.

Conclusions:

• The human motor system exhibits rapid and specific adaptation to prism-induced visual perturbations.
• Motor learning through prism adaptation involves recalibration of sensorimotor relationships across multiple body segments.
• Long-term motor adaptations are robust and retained for extended periods, demonstrating significant neuroplasticity.