Basal Ganglia Circuits — Physiology

A 45-year-old man with a unilateral subthalamic nucleus (STN) lesion from a small stroke presents with contralateral hemiballismus, while a patient with bilateral striatal dopamine depletion (advanced Parkinson disease) presents with bradykinesia and rigidity. Which feature best discriminates the circuit dysfunction underlying these two presentations?

In the basal ganglia circuits, the direct pathway is characterized by which neurotransmitter released from the striatum to the globus pallidus internus (GPi)?

Which is the most common excitatory neurotransmitter released by the thalamocortical neurons projecting to the motor cortex in the basal ganglia circuit?

A 42-year-old woman from Mumbai presents with involuntary choreiform movements of her limbs, emotional lability, and cognitive decline over the past 18 months. Her father died at age 55 with similar symptoms. Genetic testing confirms a CAG trinucleotide repeat expansion in the huntingtin gene. Which basal ganglia circuit dysfunction best explains her hyperkinetic movement disorder, and what is the underlying neurochemical imbalance?

A 52-year-old woman from Mumbai presents with involuntary choreiform movements of the limbs, emotional lability, and cognitive decline over 18 months. Family history reveals her father died of a similar illness at age 55. Genetic testing confirms CAG trinucleotide repeat expansion in the huntingtin gene. Which investigation is most appropriate to assess the structural and functional integrity of the basal ganglia circuits and correlate with disease severity?