Q. A 70 year-old male presents to the emergency room with altered mental status. His wife notes that the patient has difficulties with orientation and keeping up with conversations that started two days ago. His past medical history includes chronic alcohol use disorder drinking 5-6 beers daily for the last 25 years. His vitals are normal. On neurological examination, the patient is disoriented to person, place, and time. He is noted to confabulate answers during the examination. His cranial nerve testing reveals gaze evoked binocular horizontal nystagmus. He has a wide-based gait. The remainder of his neurological and medical exam is unremarkable. Which of the following structures below is most likely to be affected in this patient?