Final answer:
Brenda's Aunt Shelby's failure to remember details from attending school with Bruce Springsteen is likely retrograde amnesia, a loss of the ability to retrieve stored long-term memories from before a certain point.
Step-by-step explanation:
The inability of Brenda's Aunt Shelby to recall her long-term memories about attending elementary school with Bruce Springsteen is most likely an example of retrograde amnesia. This form of amnesia affects the retrieval of information stored in long-term memory prior to a certain point, which can be due to normal aging, psychological or physical trauma. Since Aunt Shelby is simply struggling to remember past events from many years ago, and not facing difficulty in forming new memories, it is not anterograde amnesia, which involves an inability to form new memories after the point of trauma.
The situation described does not match transient global amnesia, which is a temporary loss of all memory, nor source amnesia, which involves being unable to recall how one obtained a certain piece of information. Retrograde amnesia can vary greatly in severity from mild cases, where specific details may be fuzzy, to severe cases where individuals can't recall large swathes of their personal history.