Okay, let's tackle this question. The question is about which part of the brain is affected when there's an embolism in the posterior cerebral artery, leading to memory impairment. First, I need to remember the territories supplied by the posterior cerebral artery. The posterior cerebral artery mainly supplies the occipital lobe and parts of the temporal lobe. But memory is more associated with the medial temporal lobe structures like the hippocampus and amygdala.

Wait, the posterior cerebral artery does supply the hippocampus, right? Because the medial temporal lobe, including the hippocampus, is part of the limbic system and is supplied by the posterior cerebral artery. So if there's an embolism here, that area would be damaged, leading to memory issues. The hippocampus is crucial for forming new memories.

The options aren't provided, but common distractors might include the parietal lobe, thalamus, or other areas. For example, if an option says "parietal lobe," that's incorrect because the parietal lobe is more involved in sensory processing and spatial awareness. The thalamus is a relay station, but it's supplied by other arteries. The anterior cerebral artery supplies the medial frontal lobe, which isn't related to memory. The middle cerebral artery affects the lateral temporal and frontal lobes, which are more involved in language and motor functions.

The clinical pearl here is that the posterior cerebral artery territory includes the hippocampus, so infarction here leads to anterograde amnesia. This is a classic sign of Wernicke's encephalopathy, but that's due to thiamine deficiency. Wait, no, Wernicke's is more about the mammillary bodies and thalamus. Maybe the key point is that the hippocampus is supplied by the posterior cerebral artery, and damage here causes memory impairment. So the correct answer would be the medial temporal lobe structures, specifically the hippocampus. The wrong options would be other regions supplied by different arteries.

So, the core concept is knowing the vascular supply of the hippocampus and its role in memory. The correct answer is the hippocampus, and the incorrect options are other brain regions not supplied by the posterior cerebral artery. The clinical pearl is that posterior cerebral artery embolism can lead to memory deficits due to hippocampal damage.

**Core Concept**
The posterior cerebral artery (PCA) supplies the medial temporal lobe, including the hippocampus and amygdala, which are critical for memory formation. Embolism in this artery disrupts blood flow, leading to ischemic damage in these structures.

**Why the Correct Answer is Right**
The hippocampus, a key structure for declarative memory consolidation, is a terminal branch of the PCA. Ischemia here results in anterograde amnesia (inability to form new memories). The PCA also supplies the medial temporal lobe’s parahippocampal gyrus, further linking its territory to memory impairment.

**Why Each Wrong Option is Incorrect**
**Option A:** *Parietal lobe* is supplied by the middle and anterior cerebral arteries, not the PCA. Damage here affects sensory integration, not memory.
**Option B:** *Thalamus* is perfused by the posterior cerebral and basilar arteries but primarily serves as a sensory relay; its damage causes sensory

✓ Correct Answer: A. Hippocampal gyrus