Final answer:
The Medial Vestibulospinal Tract is responsible for the reflex activation of neck muscles to regulate head position in response to semicircular canal stimulation, contributing to balance and visual attention coordination.
Step-by-step explanation:
The tract responsible for regulating head position by reflex activation of neck muscles in response to stimulation of the semicircular canals is the Medial Vestibulospinal Tract. This tract is part of the vestibulospinal system, which connects the brain stem nuclei of the vestibular system with the spinal cord allowing posture, movement, and balance to modulate based on equilibrium information from the vestibular system. The vestibulospinal tract in particular assists in the coordination of eye and head movements to maintain visual attention and balance.