We are always discussing how the brain works to create memories, but do not often test the waters in how our brain holds the memories we have already stored there. Healthy brains are able to store memories in different regions – depending on what the memory is used for. What about people who have sustained brain damage? What happens to the memories they create?
In order to understand how the brain stores and recalls memory you can use the picture of a family reunion or wedding for example, and recall people and activities during that event. A normal person will be able to recognize the faces of the people they know and put a name to them. They will recall something that may have been taken place when the picture was taken. People who have anterograde amnesia, however, can recall the pictures and activities perfectly, before they sustained their brain trauma, but are not able to make new memories. They live permanently in the present. Their speech and general knowledge is intact, but forming new memories is not possible. This is because the activity they can recall was not stored in the hippocampus. 
Eleanor Maguire, Professor of Cognitive Neuroscience at the Wellcome Trust Centre for Neuroimaging at UCL, London says: “If they (people with anterograde amnesia) so a couple of hours of tests with me, for example, and I leave the room for ten minutes and come back, they can’t remember anything about me or what they had been doing. They can’t live alone because they can’t remember if they turned the gas off or paid their bills. Sometimes, which is very sad, if a spouse dies, they can’t remember their loved one is now gone.”
Maguire and her team of researchers are extremely interested in how the hippocampus works with people who have experienced brain trauma. In order to see how damaged brains the researchers have to first find out how normal brains process memory. Volunteers had their brains scanned using an fMRI (Functional Magnetic Resonance Imaging) scanner and a computer studied the patterns created while the subjects viewed three short films of people performing everyday tasks, and then when they were asked to memorize what they saw.
Even though the brain uses a network of connections to support memory, the computers worked best at analyzing the data from the fMRI scans when there was activity in the hippocampus. This would then conclude the hippocampus region is most important in recalling episodic memories, and our memories are encoded within the brain predictably. The researchers were then able to identify the exact circuits used to recall a particular memory in the brain. “That is very exciting because it means we can look at specific memory traces,” says Maguire.
From this information Maguire believes it is possible to find out precisely which areas of the brain hold certain memories, how this trace varies with time, and what happens to it as a result of traumatic brain injury.
Confirming that the hippocampus plays a key role in recalling past events, Maguire and her colleagues also found another interesting discovery, that people with brain damage had trouble imagining, visualizing or describing in detail everyday situations. Their ability to construct future and fictitious events was also severely impaired. “The role played by the hippocampus in processing memory was far broader than merely reliving past experiences,” Maguire says. “It also seems to support the ability to imagine any kind of experience including possible future events. That is why, in this sense, people with damage to the hippocampus are forced to live in the present.”
She is also eager to apply her work to novel treatments for memory disorders. “We have found that structural changes can occur in healthy human brains. Perhaps in the future we could use that kind of understanding to help people with hippocampal damage.” But, of course, many other circuits are involved in memory. “When we use fMRI, other brain regions are engaged also. We still don’t know a great deal about what they are doing. Until we do, it won’t be possible to design a memory rehabilitation programme with confidence.”
This article was shared by two time USA Memory Champion and memory speaker, Ron White.
Resources:
Welcome Trust – Mapping Memories: Eleanor Maguire and Brain Mapping: http://www.wellcome.ac.uk/News/2011/Features/WTVM052016.htm