A 63-year-old man comes to the emergency department after sudden onset of severe vertigo, nausea, and vomiting. He says the room is “spinning,” and he has difficulty walking without holding onto the wall. On exam, he has truncal ataxia and gaze-evoked nystagmus. When asked to touch his finger to his nose, his movements are relatively accurate. Strength and sensation are intact. Head impulse test is normal. MRI shows an acute infarct involving the flocculonodular lobe of the cerebellum.

Which of the following structures is the most direct downstream target of the deep cerebellar nucleus that primarily receives Purkinje cell output from this cerebellar region?