KIN 313 Lecture 13: Proprioception and Kinaesthesis 1

4 sources of proprioception/kinaesthesis

1. Muscle spindle (velocity and length of muscle)

2. Skin (length and velocity of skin stretch, onset of movement, acceleration, etc)

• FA1 and FA2 tell you what’s going on, FA2 tells acceleration, especially if you hit something.

3. GTO (active tension/force)

4. Joint (pressure, contraction sensitivity of spindles)

• (not good at this other than modulating spindle sensitivity)

kinaesthesis vs proprioception

kinaesthesis = conscious, subject to interpretation

• movement sense: what is my thumb doing, how fast is a limb moving

proprioception = not conscious, more reflexive

• position sense: where is my thumb, where is a limb moving

4 major contributors to Kinaesthesis

1. Sense of position and movement of the limbs

2. sense of tension or force

3. sense of effort or heaviness

4. sensations of body image and posture

How do we know that spindles play a conscious role in position/movement sense?

• Vibration of a muscle causes spindles to fire at the rate of vibration

• this leads to perception that the vibrated muscle is longer than it actually is (increased discharge perceived as representing a longer muscle length)

• causes limb velocity illusions/dissociations (increased velocity code) and limb length/position illusions/dissociations (increased length code)

• size of illusions directly related to frequency of the vibration (faster vibration = more illusion) → illusions = frequency dependent

• shows not only is the spindle code there, but we use it selectively

For fast movements, muscle spindles in agonist muscles go quiet/unloaded → even y drive can’t keep up. so how do we know where our limb is? how was this proven?

Spindles in antagonist still work great bc muscle is lengthening. they work without gamma and will just work extra good with gamma

Showed this by flexing arms at a speed too fast for gamma drive to keep up. Looked at illusions when vibrating antagonist, agonist, or nothing.

At this speed of flexion, vibration of the antagonist caused illusions of the joint being more flexed than in reality, showing the spindles are important in the antagonist. Vibration of the agonist caused no illusion, showing the spindles in the agonist are not used at this speed

How do we know spindles are important to position movement sense

vibratory illusions

and when we removed all other feedback at a joint except spindles, participants could still feel the movement. or dont allow the joint to move but pull on the tendons and they “feel” the movement even tho all they have is spindles

evidence that Joint Receptors play some role in position sense

test position sense after putting slack on the tendon, therefore removing spindles

Control:

• Normal skin, normal joint, no spindles

• faster you moved, faster/sooner/at less degree of change they detected if you moved the joint and what direction

• move slowly, they took longer to notice/needed to reach more angular change before they noticed

Get rid of joint receptors:

• numbed joint receptors, no spindles, only skin

• raised threshold for noticing change

• had to move faster/induce more angular change before they noticed

• showed without joint receptors, theres a slight deficit in position sense

Enhance joint receptors:

• add saline to joint to swell it, increasing its sensitivity

• lowered threshold for noticing change

• could move slower/less angular change and theyd still notice

• showed enhanced joint receptors improve position sense

therefore, joint receptors play a role in position sense (even outside of spindles) because position sense gets worse when you remove the joint receptors and gets better when you enhance them