**Core Concept**
Wernicke-Korsakoff syndrome is a neuropsychiatric disorder caused by thiamine (vitamin B1) deficiency, often seen in chronic alcoholics. The condition involves damage to specific areas of the brain, leading to cognitive impairment and memory loss.

**Why the Correct Answer is Right**
The correct answer involves identifying the brain area not typically affected by Wernicke-Korsakoff syndrome. The key brain regions involved are the mammillary bodies, thalamus, and hypothalamus. However, the primary visual cortex is usually spared. This is because the condition primarily affects the diencephalon and the limbic system, which are not directly involved in visual processing.

**Why Each Wrong Option is Incorrect**
**Option A:** Mammillary bodies - Incorrect because the mammillary bodies are a critical area affected in Wernicke-Korsakoff syndrome, leading to significant memory and cognitive impairment.

**Option B:** Thalamus - Incorrect because the thalamus is also involved in Wernicke-Korsakoff syndrome, particularly in the Korsakoff's psychosis phase, leading to disturbances in sensory perception and memory.

**Option C:** Hypothalamus - Incorrect because the hypothalamus is affected in Wernicke-Korsakoff syndrome, contributing to endocrine disturbances, temperature regulation issues, and autonomic dysfunction.

**Clinical Pearl / High-Yield Fact**
Wernicke-Korsakoff syndrome can be prevented with thiamine supplementation in individuals at risk, such as chronic alcoholics. Early recognition and treatment are crucial to preventing the progression of the disease.

**Correct Answer: D. Primary visual cortex**