Joint Position Sense: Tuning Curves & Population Vector (2D)

Knowing your knee angle without looking at it depends on a ring of stretch-sensitive mechanoreceptors, each broadly tuned to fire most strongly near one particular angle across the joint's range of motion. This 2D companion plots every afferent's Gaussian tuning curve directly in angle space and, below it, constructs the population-vector decode as an explicit 2D vector diagram — each receptor contributing a vector along its own preferred angle, scaled by firing rate, summed into the blue estimate needle. Drag the flexion slider to move the joint and watch every tuning curve's read-out ripple, add afferent noise or remove receptors to see position sense degrade the way it does after joint injury or peripheral neuropathy, and compare the live population estimate against the true angle.