Q. An 85 year-old man presents to the ER with severe nausea and vomiting and a terrible spinning sensation. He reports that he was just fine when he went to sleep but when he rolled over when he woke up, he suddenly felt violent spinning. If he keeps perfectly still, the spinning will abate but it never fully resolves. He denies any recent sudden head movements or trauma to his neck. On examination, his vital signs are normal. When you assess his eye movements, you detect upward and counterclockwise nystagmus and suspect he is suffering from posterior semicircular canal benign paroxysmal positional vertigo. Which of the following accurately describes what is observed when a normal individual's posterior semicircular canals are activated?