Q. A 75-year-old male presents to the clinic with concerns of memory loss. He is accompanied by his wife who helps to give collateral information. She notes that over the last 3 years, he has had a gradual decline in his memory. He has difficulties following conversations, remembering appointments, and following through on tasks. He often misplaces objects and is no longer able to drive. Recently, he went for a walk in his neighborhood and he could not remember how to get back to his house. His wife had to drive around the neighborhood to find him. He does not have any abnormal movements of his arms or legs. He does not have a history of falling. He has a family history of dementia in his mother. His vitals are within normal limits. His neurological exam reveals a Mini-Mental State Examination (MMSE) score of 10. He scored a 0 on the orientation and recall portion of the exam. He has difficulties following commands. His speech, cranial nerves, strength testing, deep tendon reflexes, and gait exam are unremarkable. Which the following brain structures is most likely to be affected in this patient?