**Core Concept:**
Embolism is the blockage of a blood vessel by a foreign substance, while the posterior cerebral artery (PCA) supplies blood to the posterior aspect of the brain, including the brainstem, cerebellum, and occipital lobes. Memory impairment is a neurological symptom that can occur when blood flow to these regions is compromised.

**Why the Correct Answer is Right:**
In the context of embolism affecting the posterior cerebral artery, memory impairment occurs due to damage to the areas supplied by this artery, particularly the occipital lobes, which are crucial for visual recognition and processing, as well as memory consolidation and retrieval. The damage to these regions leads to impaired cognitive function, including memory difficulties.

**Why Each Wrong Option is Incorrect:**
A. Damage to the anterior cerebral artery (ACA) would not explain memory impairment specifically, as the ACA supplies the frontal lobes, which are primarily involved in higher cognitive functions, executive functions, and motor control.
B. Damage to the middle cerebral artery (MCA) would result in a different set of neurological symptoms, as the MCA supplies the frontal, parietal, and temporal lobes, which are responsible for sensory processing, spatial awareness, and speech respectively.
C. Damage to the internal carotid artery (ICA) would not specifically explain memory impairment, as the ICA supplies the entire brain, including both the anterior and posterior circulation, but not the specific regions associated with memory.

**Why the Correct Answer is Right:**
The correct answer (D) focuses on the posterior cerebral artery, which supplies the occipital lobes, brainstem, and cerebellum, all of which are essential for visual recognition, processing, and memory consolidation. Damage to these regions results in memory impairment as observed in memory deficits following posterior cerebral artery embolism or occlusion.

**Clinical Pearl:**
The posterior cerebral artery is crucial for maintaining visual recognition and processing, as well as memory consolidation and retrieval. Recognizing the specific artery involved can help guide differential diagnosis and anticipate the neurological symptoms resulting from its occlusion or embolism.