he knew his parents and the layout and location of his childhood home, and had apparently normal memories of his childhood. This meant that the operation carried out on H.M. impaired his ability to lay down new memories but spared his general intelligence (for example, he still continued to enjoy doing crossword puzzles—though he could do the same one over and over) and generally spared his memories of events that occurred before his operation.
This showed that Lashley’s theory was wrong: There is a particular part of the brain that is specifically involved in allowing us to create new memories. What part of the brain was it? This is where Scoville and Milner were appropriately cautious. H.M.’s operation damaged both the hippocampus and the amygdala on both sides of the brain. This general region of the brain that houses the hippocampus and amygdala is often referred to as the medial temporal lobe. That is, it’s the part of the brain’s temporal lobe located toward the middle of the brain ( medial in anatomical terminology). But in examining the nine other psychiatric patients who had varying amounts of medial temporal lobe damage, Scoville and Milner noticed that the more the hippocampus was damaged on both sides, the more severe the memory deficit. This led them to suggest that the large extent of hippocampal damage on both sides was likely underlying the severe memory deficit in H.M.; however, they could not rule out the possibility that concurrent damage of the amygdala plus the hippocampus was at the root of the memory loss.
THE FASCINATING STORY OF PATIENT H.M.
Patient H.M. is one of the most fascinating and most extensively studied neurological patients in the learning and memory literature. After Brenda Milner’s work with him, her then graduate student and now professor emerita at MIT Suzanne Corkin studied H.M. for a total of forty-seven years, until his death in 2008. If you want to know more about patient H.M. and his story, I recommend Corkin’s wonderful book, Permanent Present Tense: The Unforgettable Life of the Amnesic Patient H.M. Listen to me interview Suzanne about H.M. on the podcast Transistor by PRX.
But this was not all Milner noticed. Once she characterized the severity of H.M.’s everyday memory loss, she got to work figuring out if there was anything at all he could learn and remember normally. She and others later showed that H.M. had an inability to form any new memories for facts (termed semantic memory) or events (termed episodic memory), typically referred to together as declarative memory—the kind of memory that can be consciously brought to mind. Next Milner revealed that H.M. did have normal memory for some things. Namely, she showed that he still had the ability to learn new motor or perceptual skills at the same rate as people who had not undergone surgery. Milner had him do tests in which he had to learn how to trace a figure accurately while looking in a mirror. H.M. improved steadily day by day but, strikingly, had no memory of ever having done the task before. Similarly, he was able to learn perceptual tasks in which he was given a vague outline of a picture and, after a variable amount of time looking at the incomplete figure, gradually picked out the image. He learned to identify those objects at the same rate as nonpatients as well. This was another revelation in the memory field. This finding suggested that different brain areas outside of the hippocampal region were necessary for these forms of motor and perceptual memory.
So the partnership of Scoville and Milner revolutionized the way we understand memory. Their studies led to our understanding that the medial temporal lobe, which includes the hippocampus, is essential for our ability to form new memories for facts and events. The researchers also showed that memories are not stored in the hippocampus because H.M. retained normal memories of his childhood and demonstrated that different forms of memory,
This showed that Lashley’s theory was wrong: There is a particular part of the brain that is specifically involved in allowing us to create new memories. What part of the brain was it? This is where Scoville and Milner were appropriately cautious. H.M.’s operation damaged both the hippocampus and the amygdala on both sides of the brain. This general region of the brain that houses the hippocampus and amygdala is often referred to as the medial temporal lobe. That is, it’s the part of the brain’s temporal lobe located toward the middle of the brain ( medial in anatomical terminology). But in examining the nine other psychiatric patients who had varying amounts of medial temporal lobe damage, Scoville and Milner noticed that the more the hippocampus was damaged on both sides, the more severe the memory deficit. This led them to suggest that the large extent of hippocampal damage on both sides was likely underlying the severe memory deficit in H.M.; however, they could not rule out the possibility that concurrent damage of the amygdala plus the hippocampus was at the root of the memory loss.
THE FASCINATING STORY OF PATIENT H.M.
Patient H.M. is one of the most fascinating and most extensively studied neurological patients in the learning and memory literature. After Brenda Milner’s work with him, her then graduate student and now professor emerita at MIT Suzanne Corkin studied H.M. for a total of forty-seven years, until his death in 2008. If you want to know more about patient H.M. and his story, I recommend Corkin’s wonderful book, Permanent Present Tense: The Unforgettable Life of the Amnesic Patient H.M. Listen to me interview Suzanne about H.M. on the podcast Transistor by PRX.
But this was not all Milner noticed. Once she characterized the severity of H.M.’s everyday memory loss, she got to work figuring out if there was anything at all he could learn and remember normally. She and others later showed that H.M. had an inability to form any new memories for facts (termed semantic memory) or events (termed episodic memory), typically referred to together as declarative memory—the kind of memory that can be consciously brought to mind. Next Milner revealed that H.M. did have normal memory for some things. Namely, she showed that he still had the ability to learn new motor or perceptual skills at the same rate as people who had not undergone surgery. Milner had him do tests in which he had to learn how to trace a figure accurately while looking in a mirror. H.M. improved steadily day by day but, strikingly, had no memory of ever having done the task before. Similarly, he was able to learn perceptual tasks in which he was given a vague outline of a picture and, after a variable amount of time looking at the incomplete figure, gradually picked out the image. He learned to identify those objects at the same rate as nonpatients as well. This was another revelation in the memory field. This finding suggested that different brain areas outside of the hippocampal region were necessary for these forms of motor and perceptual memory.
So the partnership of Scoville and Milner revolutionized the way we understand memory. Their studies led to our understanding that the medial temporal lobe, which includes the hippocampus, is essential for our ability to form new memories for facts and events. The researchers also showed that memories are not stored in the hippocampus because H.M. retained normal memories of his childhood and demonstrated that different forms of memory,
Similar Books
