**Core Concept:**
Embolism is the obstruction of a blood vessel by a foreign substance or blood clot. Posterior cerebral artery (PCA) is one of the four major cerebral arteries supplying blood to the brain, particularly the occipital and parietal lobes. Memory impairment is a potential complication of embolism affecting the PCA due to damage to specific brain regions involved in memory processing.

**Why the Correct Answer is Right:**
In the context of embolism affecting the PCA, memory impairment occurs due to damage to the hippocampus and entorhinal cortex. These regions are crucial for the formation, consolidation, and retrieval of memories. Damage to these areas can disrupt these memory processes leading to cognitive impairment, specifically affecting long-term declarative memory.

**Why Each Wrong Option is Incorrect:**
A. Angiography is a diagnostic imaging procedure that involves injecting contrast media into the bloodstream to visualize blood vessels, not a cause of memory impairment.
B. The thalamus is involved in sensory processing and motor control, not directly responsible for memory.
C. The cerebellum is responsible for motor control and balance, not directly related to memory impairment.
D. The basal ganglia are involved in motor control, coordination, and learning, not directly related to memory impairment.

**Clinical Pearl / High-Yield Fact:**
The posterior cerebral artery supplies blood to the occipital and parietal lobes, which are responsible for visual perception, processing, and integration of sensory information. Embolism affecting the PCA can lead to visual and cognitive deficits, including memory impairment. Understanding the role of the hippocampus and entorhinal cortex in memory formation and retrieval is crucial for recognizing and managing potential complications of PCA embolism.