When you spin, your endolymph moves against hair cells in your semicircular canals. This tells your brain that you are spinning. But the hair cells respond strongly to changes in movement, and when you continue to spin, there is no change in movement—your vestibular system is telling your body that you aren’t really moving much, rather, the world is spinning, and you are still. This leads to sensory integration issues, and you start to feel dizzy and nauseous. Stopping spinning doesn’t help too much—suddenly your hair cells get a jerk from you stopping spinning, and say that you are moving when you are not, and you get more conflicting sensory information.
When you start spinning again, you get consistent sensory inputs—your vestibular system tells you that you are spinning, and you are. This is a good thing for maybe a spin or two, but then you will start getting conflicting input again, and get dizzier. I’m not sure that it matters which direction you spin. It is possible that the continuing motion of your endolymph (in the direction you were spinning) might be enough to lessen the triggering of hair cells when you start to spin in the same direction, while spinning in the opposite direction (against the flow) gives a stronger trigger. But that is speculation on my part.
Footnote: When dancers turn their heads to focus on a single spot, this works both because they are consistently orienting themselves visually, and because the sudden movements of their head tells their vestibular system that they are spinning—no conflict in sensory input.
When you spin, your endolymph moves against hair cells in your semicircular canals. This tells your brain that you are spinning. But the hair cells respond strongly to changes in movement, and when you continue to spin, there is no change in movement—your vestibular system is telling your body that you aren’t really moving much, rather, the world is spinning, and you are still. This leads to sensory integration issues, and you start to feel dizzy and nauseous. Stopping spinning doesn’t help too much—suddenly your hair cells get a jerk from you stopping spinning, and say that you are moving when you are not, and you get more conflicting sensory information.
When you start spinning again, you get consistent sensory inputs—your vestibular system tells you that you are spinning, and you are. This is a good thing for maybe a spin or two, but then you will start getting conflicting input again, and get dizzier. I’m not sure that it matters which direction you spin. It is possible that the continuing motion of your endolymph (in the direction you were spinning) might be enough to lessen the triggering of hair cells when you start to spin in the same direction, while spinning in the opposite direction (against the flow) gives a stronger trigger. But that is speculation on my part.
Footnote: When dancers turn their heads to focus on a single spot, this works both because they are consistently orienting themselves visually, and because the sudden movements of their head tells their vestibular system that they are spinning—no conflict in sensory input.