A 68-year-old man presents with a 3-year history of progressive memory loss affecting recent events, with preserved recall of distant memories. His daughter reports increasing difficulty with executive tasks and language. MRI shows bilateral medial temporal and hippocampal atrophy. Cerebrospinal fluid analysis reveals low Aβ42 and elevated phospho-tau. Neuropathological examination would reveal the structure marked **A** in the diagram as intracellular aggregates composed of hyperphosphorylated tau forming paired helical filaments. According to Braak staging, the distribution of these structures initially correlates with pathology in which region?