Final answer:
The hippocampus is the brain area that is affected first in Alzheimer's disease, leading to deficits in memory.
Step-by-step explanation:
The hippocampus is one of the earliest brain areas to be affected by Alzheimer's disease (AD). The hippocampus is responsible for learning and memory, so when it is damaged, it can lead to deficits in memory. For example, individuals with AD may have trouble remembering where they placed objects, recent conversations, and appointments.