Final answer:
H.M.'s memory loss after his surgery is best described as Anterograde amnesia (declarative memory), as he couldn't form new episodic or semantic memories but could learn new procedural tasks without recalling the learning process.
Step-by-step explanation:
The memory loss suffered by H.M. after his surgery is best described as Anterograde amnesia (declarative memory). H.M. was unable to form new episodic or semantic memories, which fall under declarative memory, after the bilateral removal of his hippocampus and amygdala. Although he exhibited some retrograde amnesia, it was the anterograde amnesia that was most prominent and was characterized by his inability to remember reading a magazine or recognizing new people. However, H.M. was still able to form new procedural memories, which are nondeclarative in nature, demonstrated by his increased efficiency at solving a puzzle despite not remembering previous attempts.