In the
field of neurobiology, patient HM is probably one of the most recognized cases
of amnesia. Patient HM had suffered from severe epileptic seizures so he was
given a bilateral medial temporal lobectomy. This removed the region of the
brain, which includes the hippocampus, that is important for declarative memory
storage. Declarative memory can be classified as semantic memory, memory of
facts, or episodic memory, memory of events.
The surgery was a success but
patient HM suffered from anterograde amnesia because he no longer had the
capacity to store new long-term memories. Anterograde amnesia is the
incapability of remembering events that occurred after brain damage. Patient HM
could remember all the memories of his life that happened before the surgery,
like who his wife was and where they lived, but he could not store any
long-term memories after this point. He still had his short term memory intact
so he could carry on conversations, but after a few hours he would not remember
that he had that conversation. The loss of long-term memory made patient HM
only live in the moment and he described the feeling as “like waking from a
dream. I just don’t remember.”
The second most famous amnesiac patient would probably be a patient named EP. The case of patient EP included radical memory loss due to viral encephalitis which caused large lesions in the patient’s medial temporal lobe leading to the loss of his amygdala and hippocampus. The memory loss from patient EP not only affected his ability to store new memories, but it also damaged his old semantic memories. The loss of semantic memory was because the lesions were large enough that it disrupted connectivity in the adjacent brain tissue.
The second most famous amnesiac patient would probably be a patient named EP. The case of patient EP included radical memory loss due to viral encephalitis which caused large lesions in the patient’s medial temporal lobe leading to the loss of his amygdala and hippocampus. The memory loss from patient EP not only affected his ability to store new memories, but it also damaged his old semantic memories. The loss of semantic memory was because the lesions were large enough that it disrupted connectivity in the adjacent brain tissue.
Retrograde amnesiacs usually cannot
remember things from a few months to years prior to the brain damage, but
patient EP could not remember any memories dating all the way back to 50 years
prior to the brain encephalitis. Researchers believe that this is because of
connections in the lateral temporal lobe were damaged. Although these two
amnesiac cases are tragic, they have been able to help researcher better
understand how memories are storied in the human brain.
Posted by Poya Jafari (2)
If you are interested in this subject, you should take Psych 330, Behavioral Neuroscience, or something like that. You spend at least one lecture or two learning about Retrograde amnesia and patient HM!
ReplyDeleteCynthia Bui (1)
Have there been any discoveries on how to go about curing or aiding in memory recall for these types of patients? This is a very interesting topic,and I am taking the psych 330 next semester.
ReplyDeleteTonya Sulham (3)
I wonder how these patient's lives have changed since the surgery in terms of their relationships and jobs. I wonder if the surgery was worth it to them, considering they traded in their memory to stop their seizures. I think this was definitely a breakthrough in medicine, to learn that a piece of someone's brain could be removed to prevent seizures and they could still live happily. I wonder if there is a way that they could prevent lateral temporal lobe damage to prevent the memory loss from occurring in this type of surgery.
ReplyDeleteLindsey Dugas (1)
When were these subjects well known? Are they from the time of Phineas Gage, before, or after?
ReplyDelete-Ashley Sterpka (1)
Patient HM was revealed later to be a man named Henry Molaison who lived from 1926-2008, and he had the lobectomy in 1953. Researchers published papers using the pseudonym HM for Mr. Molaison to keep him anonymous. Patient EP was diagnosed with viral encephalitis in 1992 at the age of 70 and was able to live for another 16 years.
DeletePosted by Poya Jafari (2)
So, does this mean that the doctors didn't know removing the hipppocampus from the patient HM would cause him to suffer from anterograde amnesia? Same for patient EP: were the scientist unaware of the functions of amygdala and hippocampus at that time and they came up with the results after doing the surgery on this patient?
ReplyDeleteThis article is very interesting and scary at the same time!!!
Setareh Sepasi (3)
Before patient HM's surgery, it was only hypothesized that the hippocampus was involved in memory consolidation. Patient HM's case helped scientists determine how memories are stored and what types of memories are associated with the hippocampus. They learned that short-term and procedural memory may not be affected by removing the hippocampus but long-term episodic memory is definitely impaired.
DeletePosted by Poya Jafari (2)
This comment has been removed by the author.
ReplyDeleteThis article provides a solution to one problem at the expense of a different problem and I would be interested to see how the patients feel about the cost outweighing the benefit. I would hope that these procedures can be used as a vehicle to increase our knowledge of improving ways for a higher benefit with respect to the cost.
ReplyDeleteMarshall Moini(2)