The neurological patient H.M. has suffered a severe form of which kind of amnesia?

A) anterograde amnesia for declarative memories
B) retrograde amnesia for short-term memories
C) retrograde amnesia for implicit memories
D) anterograde amnesia for procedural memories

H.M. suffered from anterograde amnesia for declarative memories, meaning he was unable to form new memories of facts and events after his surgery to remove parts of his medial temporal lobe, including the hippocampus. He was still able to retain some procedural memories, such as how to ride a bicycle, indicating that his implicit memory was intact. He also had some retrograde amnesia for events prior to his surgery, but this was not as severe as his anterograde amnesia.