Final answer:
Patient H.M.'s memory impairments, particularly his inability to remember events two years prior to his surgery and to form new memories post-surgery, are attributed to the removal of his hippocampus and amygdala. This led to anterograde and partial retrograde amnesia as these brain regions are critical for memory consolidation.
Step-by-step explanation:
The case of Henry Molaison, also known as patient H.M., provides critical insights into the process of memory consolidation. After undergoing surgery to remove his hippocampus and amygdala to alleviate seizures, H.M. developed anterograde amnesia, affecting his ability to form new episodic memories, while still retaining some short-term memory and the ability to acquire procedural memories. The hippocampus is known to play a key role in the consolidation of short-term memories into long-term memory; its removal thus prevented H.M. from transferring new experiences into long-term storage, effectively causing his memory impairments.
H.M.'s retrograde amnesia, where he couldn't remember events from the two years before his surgery, demonstrates the theory that recent memories are not fully consolidated and can be lost if the hippocampus is damaged before the consolidation process is complete. Consolidation refers to the process by which the brain converts short-term memories into long-term ones, and since H.M.'s medical temporal lobes were removed, he was unable to consolidate new information, leading to his inability to form new semantic and episodic memories post-surgery.