Neuroscience MCAT Practice Question
A 58-year-old man presents with a 6-month history of progressive incoordination and difficulty with fine motor tasks. He reports dropping objects and having trouble with rapid alternating movements. On examination, he demonstrates dysmetria on finger-to-nose testing, dysdiadochokinesia, and an ataxic gait. Romberg test is negative. Deep tendon reflexes are normal and symmetric, and strength is 5/5 throughout. MRI shows cerebellar atrophy without evidence of acute infarction or demyelination. Serum vitamin B12 and folate levels are normal. What is the primary neurophysiological deficit underlying this patient's symptoms?
Answer choices
- ALoss of proprioceptive relay neurons in the dorsal root ganglia
- BImpaired motor learning and error correction through decreased long-term depression at cerebellar parallel fiber-Purkinje cell synapsesCorrect answer
- CDemyelination of corticospinal tract fibers in the internal capsule
- DDisruption of vestibular nuclei output affecting balance reflexes
- EDamage to the spinocerebellar tracts preventing sensory input to the cerebellum
- FDegeneration of anterior horn cells causing denervation of intrinsic hand muscles
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.