**Core Concept**
Vascular dementia is a type of dementia that results from reduced blood flow to the brain, typically due to a series of small strokes or changes in the brain's blood vessels. This condition is often associated with cognitive decline, particularly in executive function and memory.

**Why the Correct Answer is Right**
The correct answer is related to the primary cognitive symptoms of vascular dementia. Memory deficits are a hallmark of this condition, often manifesting as difficulty learning new information, recalling recent events, or finding the right words. This is due to the damage caused by reduced blood flow to the brain's temporal lobes, which are critical for memory processing. In contrast, emotional lability and visual hallucinations are more commonly associated with dementia with Lewy bodies, while disorientation and personality deterioration can be seen in various forms of dementia.

**Why Each Wrong Option is Incorrect**
* **Option A:** Disorientation is a symptom that can be seen in various forms of dementia, including Alzheimer's disease, but it is not as specific to vascular dementia as memory deficits.
* **Option C:** Emotional lability is a symptom that is more commonly associated with dementia with Lewy bodies, a different type of dementia that is characterized by fluctuations in cognitive function and visual hallucinations.
* **Option D:** Visual hallucinations are also more commonly seen in dementia with Lewy bodies, which is a distinct clinical entity from vascular dementia.
* **Option E:** Personality deterioration can be seen in various forms of dementia, including Alzheimer's disease, but it is not as specific to vascular dementia as memory deficits.

**Clinical Pearl / High-Yield Fact**
Vascular dementia is often referred to as "multi-infarct dementia" due to the underlying pathology of small strokes or changes in the brain's blood vessels, which can lead to cognitive decline.

**Correct Answer:** b. Memory deficits