A 72-year-old man with Parkinson disease on maximum-tolerated levodopa-carbidopa and ropinirole presents with worsening freezing episodes and bradykinesia. Vital signs: BP 138/82, HR 68, RR 16, Temp 37°C, SpO2 98% on room air. Motor examination reveals rigidity and postural instability; cognition remains intact. Recent MRI shows no structural lesions. Deep brain stimulation is being considered for symptomatic management. Which of the following structures is a common target for this intervention?

1. A)Subthalamic nucleusGABARITO
2. B)Caudate head
3. C)Mammillary body
4. D)Nucleus accumbens
5. E)Lateral geniculate nucleus