Neuroanatomy: basal ganglia circuitry: practice question

A Anatomy question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Anatomy · Neuroanatomy: basal ganglia circuitry

Sample item

In Parkinson disease, loss of dopaminergic input to the striatum produces bradykinesia through which change in basal ganglia circuitry?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Excess inhibitory output from globus pallidus internus

Loss of dopamine weakens the direct pathway and strengthens the indirect pathway, so the subthalamic nucleus becomes overactive and the globus pallidus internus inhibits the thalamus excessively. Reduced thalamocortical drive explains the difficulty initiating movement.

Option by option

  • A. Excess inhibitory output from globus pallidus internus (correct)

    Correct. Excessive pallidal inhibition lowers thalamic drive to the motor cortex.

  • B. Increased thalamic excitation of motor cortex

    Thalamic excitation of the cortex is reduced in this state, not increased.

  • C. Reduced excitatory drive from subthalamic nucleus

    The subthalamic nucleus becomes overactive, not underactive, once the indirect pathway dominates.

  • D. Disinhibition of thalamus by the direct pathway

    The direct pathway is weakened in Parkinson disease, so it cannot disinhibit the thalamus.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is A, Excess inhibitory output from globus pallidus internus. Loss of dopamine weakens the direct pathway and strengthens the indirect pathway, so the subthalamic nucleus becomes overactive and the globus pallidus internus inhibits the thalamus excessively.

Why is "Increased thalamic excitation of motor cortex" not the answer?

Thalamic excitation of the cortex is reduced in this state, not increased.

Why is "Reduced excitatory drive from subthalamic nucleus" not the answer?

The subthalamic nucleus becomes overactive, not underactive, once the indirect pathway dominates.

Why is "Disinhibition of thalamus by the direct pathway" not the answer?

The direct pathway is weakened in Parkinson disease, so it cannot disinhibit the thalamus.

What concept does this question test?

It tests Neuroanatomy: basal ganglia circuitry in Anatomy. Reduced thalamocortical drive explains the difficulty initiating movement.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Neuroanatomy: basal ganglia circuitry?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.