Proprioception and Movement Control

Proprioception

• Proprioception is the ability to perceive the position and movement of body parts, without visual input.
• It includes sensing force, heaviness, and muscle tension.
• Proprioception is used for tasks like touching one's nose with their fingers, even with eyes closed.

Proprioceptors

• Mechanoreceptors are the basis of proprioception, located in the locomotor system.
• Muscle spindle receptors sense stretching.
• Golgi tendon organs sense tendon tension.
• Joint receptors sense joint position.
• Skin mechanoreceptors contribute to proprioception.
• Efferent copy (sense of effort) helps predict motor command consequences.

Importance of Proprioception

• Crucial for smooth, controlled movements.
• Without accurate proprioception, people may not be able to control movements even if visual information is present.
• They may lose awareness of their body's position.
• Loss of body ownership can occur.

Proprioception and Movement Control

• Proprioceptive information is used at all levels of movement control.
• From basic automatic responses (like the knee-jerk reflex) to more complex, conscious actions (like balancing).
• Proprioception is integrated with other sensory modalities (like vision, touch).
• Balance is often assessed with visual input, however, its assessment can also include vestibular, tactile, and proprioceptive input.
• Balancing is important for performance in sports, and the prevention of injuries, especially for elderly people.

Assessing Proprioception

• Formal tests, such as joint position reproduction, are employed.
• Testing can involve measuring posture stability, and how well someone can maintain balance.
• Visual cues are often involved in balance tests, but balance tests also exist without visual cues.

Rubber Hand Illusion (RHI)

• The RHI demonstrates sensory integration.
• Visual and tactile input can override proprioceptive information.
• Experimenter covers one hand, places a rubber hand in front of participant.
• Touching the rubber hand synchronously with the unseen real hand causes participants to perceive the rubber hand as part of their body.

Proprioceptive Accuracy

• Proprioception accuracy varies among individuals.
• Performance declines with age.
• Proprioception accuracy is linked to motor skill performance and can be useful in diagnosing conditions like Parkinson's disease, and cerebral palsy..
• Proprioceptive training can be used to improve accuracy and regulation of movement.