I’ve been developing an interest in the role that the frontal lobes play in memory. We traditionally think of memory as heavily based in the medial temporal lobes. At least, the medial temporal lobes are larely responsible for the creation of new memories. Without the hippocampus and the surrounding area people have anterograde amnesia, which is the inability to form new memories. The classic and most well known example of this is the patient H.M. Researchers recognize the role that other areas of the brain have in memory but most memory research has focused on the medial temporal lobes – at least until recently (with recently being the last 20 years or so). New ideas take a while to develop and gain acceptance so some of these ideas about the role of other brain areas in memory creation are still developing.
For example, we now know that when information needs to be organized, such as in something like the Rey-Osterrieth Complex Figure (read here for a short description of the test) or with a list learning task with words from specific semantic categories, the frontal lobes are involved.
If the frontal lobes are heavily involved in the organization of information it follows that memory tests that require more organization of material should be affected by dysfunctioning of the frontal lobes. Some researchers are now trying to place certain functions with greater specificity within the frontal lobes. This isn’t really phrenology because the methods of phrenology were entirely suspect. Phrenologists extrapolated personality and cognitive characteristics of people based of measurements of their skulls. Many researchers who are interested in localizing brain functions do so by testing people with specific brain
lesions (injuries). If enough patients have damage to X part of the brain and subsequently have Y deficits, then we can assume that X is necessary for Y to occur (but is not necessarily sufficient for Y to occur). Phrenologists never looked at the brain or the head in this manner. Paul Broca was one of the first, with his patient Tan, to systematically look at the relationship between brain injury and behavior.
For a long time many people believed (and many still do) that certain areas of the frontal lobes, specifically the most anterior areas of the frontal lobes, are essentially superfluous. They base this idea on cases where
people have had damage to this area of the brain but apparently suffered no ill effects. Research has consistently not supported that view. We don’t have any non-necessary brain. What we do have are tests and measures that are not sufficiently sensitive nor specific. The brain is also very complex and most functions rely on networks of brain structures. We are also learning that the white matter in the brain is very involved in behavior and cognition (this is my own area of research). The more we learn, the more we realize our ignorance about the brain. There are layers upon layers to be unwrapped and understood about the brain.
Image by Debbi in California.
The frontal lobes serve to make sure our memories are appropriate and socially acceptable. When the frontal lobe is damaged, you get a disorder like confabulation where memories are blown out of proportion and might sound absurd. Usually the confabulator is not lying. However, since their frontal lobes are damaged they are not able to censor or inhibit tangential and irrelavent memories, so things get expressed indiscriminantly. Also, you can get grandiosity with prefrontal cortex damage. People with narcissitic personality disorder often have memories which aggrandize their own life disproportionately to what they actually accomplished. So the frontal lobes serve to make sure that our memories are weighed correctly so we don’t emphasize or minimize things too much in comparison with another person’s memory
http://en.wikipedia.org/wiki/Confabulation
We know that emotions from the limbic system have an effect on encoding new memories, but what role does the frontal lobe play in encoding new memories?
We can see frontal lobe damage that can change the way we recall memories, so must there not also be a change in encoding process?
“but what role does the frontal lobe play in encoding new memories?”
I’m not positive about that. This blogger though has quite a few good posts about memory. Here’s one about the medial prefrontal cortex.
http://mindblog.dericbownds.net/2007/06/new-steps-in-memory-consolidation.html
I can speculate about a possible role of the PFC in memory consolidation. The prefrontal cortex is involved in generating interest in the world around you. Lesions of both the dorsolateral and medial prefrontal are associated with apathy or a lack of interest in your environment. The PFC serves to highlight salient things in the environment and make them interesting. Apathy is common in depression and negative schizophrenia and is associated with a lack of activity in the PFC. If you are apathetic, the days in the week may run together and all seem the same. So if your not interested in things in the environment, you are less likely to remember them. Conversely if you have a high amount of interest in the environment, your memory encoding is going to be that much greater. Taking a drug like amphetamine (adderall) increases PFC activity and can make studying more salient or interesting. So it can definitely improve a person’s memory in that way.
“The dorsolateral and medial prefrontal cortex are critical for immediate memory processing. The possibility has been raised that those two areas may also contribute to long-term memory formation.”
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WNM-4NY4WKW-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=de709f14f2c12788087714951c4af88f
From wikipedia:
http://en.wikipedia.org/wiki/Working_memory
“The PFC has been found to be active in a variety of tasks that require executive functions[35]. This has led some researchers to argue that the role of PFC in working memory is in controlling attention, selecting strategies, and manipulating information in working memory, but not in maintenance of information.”
I think that when your prefrontal cortex isn’t functioning properly your memory tends to be fragmentary and more difficult to piece together. So the prefrontal cortex serves to make sure your memories are placed in the correct context and time sequencing. This could be due to a poorer working memory that is associated with dorsolateral PFC deficits. Working memory is your ability to hold and manipulate information temporarily. Working memory can be measured by tests like the n-back. So a person with a good working memory might be able to store 3 or 4 items while a person with a poorer working memory might only be able to store 1. The fewer items you are able to store, the more disorganized your long term memory becomes. If you have a poorer working memory, then your long term memory encoding is also likely to be poor.
Sorry for the long post. I do find memory an interesting topic. I think its an extremely complex subject and not all researchers can even agree on the exact mechanisms of memory consolidation.
Interesting. I like the part where you say that we don’t have any non necessary brain. I feel like printing this and taking it to my son’s next appointment with his neurosurgeon. That way when he tells me that big ole arachnoid cyst that is displacing his left temporal lobe isn’t causing his cognitive problems I can throw this at him. Well this and the neuropsychological exam that shows he has poor executive functioning, terrible working memory, and such a wide scatter score they can’t give me an IQ….should be a fun visit.
Almost as exciting as the visit where he explained that Arachnoid Cysts only caused headaches. Then I asked if space occupying lesions caused cognitive problems. He said yes. I asked if an A.C was a space occupying lesion? He said yes, then left the room.
Good times…..good times…..
The aim of science is to discover and illuminate truth. And that, I take it, is the aim of literature, whether biography or history or fiction. It seems to me, then, that there can be no separate literature of science. Rachel Carson, author of Silent Spring
My son is 20 now but at the age of 7 his father picked him up by the neck and threw him into the wall head first. That night he had his first seizure. The Dr’s told him that they should get better with age however they have gotten so much worse. All of his EEG’S show damage to the right frontal lobe. I was unhappy with his medical care and found a highly respected Neurologist. He was the first Dr that did an MRI and found trauma to the back of his head. The Dr. asked if he knew how this happened and he said that his 250 pound father repeatedly hit him in the back of the head and then threw him into a wall. DCF was involved but did nothing. We have been divorced now for 17 years. All Michael does is sit in his room day and night and watches TV. We have just applied for SSI due to the fact that he can’t work or go to school because his memory is not working. The Neurologist wants him to go to Mayo clinic and be tested to see where it is coming from and if he can have brain surgery.
Does anybody have experience with this-if so PLEASE HELP ME -THIS IS A HUGE DECISION.