Final answer:
Magnocellular cells are part of the dorsal stream involved in motion perception, responding to the direction of movement and playing a vital role in the perception of 3-D motion.
Step-by-step explanation:
Magnocellular cells are involved in motion perception, as they respond preferentially to bars moving in a particular direction. These cells are part of the dorsal stream, which includes connections between cortical areas from the occipital to parietal lobes that are responsible for the perception of visual motion and guiding movement of the body in relation to that motion. The dorsal stream's ability to perceive motion is essential for understanding how the brain perceives 3-D motion. This perception is made possible by mechanisms such as retinal disparity and the comparison of visual stimuli between the two eyes, which can also be related to proprioception and the vestibular system.