A bilateral lesion of the mammillary bodies (as seen in Wernicke encephalopathy) primarily damages which functional circuit?

• A Dorsal stream visual processing
• B Reward circuitry via connections to nucleus accumbens
• C Papez circuit — the mammillothalamic tract to the anterior thalamic nucleus, cingulate, entorhinal cortex, hippocampus ✓
• D Hypothalamic-pituitary axis for osmoreception

Explanation

The mammillary bodies receive input from the hippocampus via the fornix and project via the mammillothalamic tract to the anterior thalamic nucleus. This is a key relay in the Papez circuit (hippocampus → fornix → mammillary bodies → mammillothalamic tract → anterior thalamus → cingulate gyrus → parahippocampal/entorhinal cortex → hippocampus), which underlies episodic memory consolidation. Bilateral mammillary body damage in Wernicke-Korsakoff syndrome causes anterograde amnesia (failure to form new memories) with relatively intact remote memories and immediate recall, characteristic of Korsakoff amnestic syndrome.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.