A 38-year-old woman from Bangalore is evaluated for progressive clumsiness over 6 weeks. She reports difficulty with rapid alternating movements of her hands and feet. On examination, she performs finger-to-nose and heel-to-shin tests with marked overshoot and oscillation of the limbs. She also demonstrates dysdiadochokinesia (inability to perform rapid alternating pronation-supination of the forearms). Her gait is relatively preserved, and she has no vertigo. Fundoscopy reveals no optic atrophy. MRI brain shows focal lesion in the right cerebellar hemisphere. Which of the following BEST explains the patient's clinical findings?