Final answer:
H.M. underwent a bilateral lobectomy to remove his medial temporal lobes, including the hippocampus and amygdala, to control his epileptic seizures, which resulted in anterograde amnesia, affecting his ability to form new long-term memories.
Step-by-step explanation:
Henry Molaison, known as patient H.M., had parts of his brain removed to treat severe seizures. Specifically, he underwent a bilateral lobectomy where both the left and right medial temporal lobes were removed, including the hippocampus and amygdala structures. The surgery was an attempt to control his epileptic seizures which were concentrated in these regions of the brain.
The consequence of the operation on H.M. was a profound impact on his memory functions. While the procedure did reduce his seizures, it resulted in H.M. developing anterograde amnesia, a condition where he could no longer form new long-term memories. H.M. could recall most events from prior to the surgery but had a partial loss of earlier memories, known as retrograde amnesia. Despite this, H.M.'s case has provided invaluable insights into the role of the hippocampus and adjacent structures in memory consolidation and learning processes.