In a series of studies, researchers tested patient H.M., who had his hippocampus and surrounding medial temporal lobe surgically removed to treat severe epilepsy. After surgery, H.M. could recall events from before the operation and could carry on a conversation, but he could not remember new acquaintances even after meeting them dozens of times. Surprisingly, he could learn new motor skills like mirror tracing, even though he had no memory of practicing them.
H.M.'s pattern of deficits provides the strongest evidence that the hippocampus is critical for which process?
- Acheck_circle
Forming new explicit (declarative) long-term memories
- B
Recognizing familiar faces seen before surgery
- C
Producing fluent speech
- D
Storing procedural skills such as bicycle riding
Explanation
H.M. could not form new explicit memories (anterograde amnesia) but retained procedural learning, showing the hippocampus is essential for encoding new declarative memories but not procedural ones. Speech production is associated with Broca's area.