Why is it difficult to learn new things after a brain injury?
In the period right after a brain injury, the problem with learning is new things is that even though the information is present and has been repeated, it doesn't sink in. So a few minutes after something has been presented, the person might not remember that it has even been discussed. Most of us don't have that experience on a day-to-day basis. If you learn something new, you might not remember the details, but at least you remember that it was presented to you. Here, it's as if the tape simply isn't recording. As a result, a few minutes later, when somebody tries to play back what happened, it's blank. There's no information there to recall.
The process of laying down information — committing it to tape — takes some days to actually recover in order for people to begin to be able to play back from their own memory a story that makes sense, one that isn't filled with gaps or with incomplete information.
There are a fair number of studies that have looked at the reasons why that learning is difficult. It may be different in the early period after injury than in the late period. Among the reasons in the early period after injury is, first, damage to the structures that we need to pay attention, to roll tape and commit things to memory, and then also to the systems that help retrieve it.
Those include the upper brain stem – keeping the lights on and beginning to pay attention, a structure we call the hippocampus, which is important for helping to lay down new memory, and then the frontal lobes, to retrieve that which has already been laid down. In addition to damage to those structures, the early period after brain injury is characterized by a huge output of all kinds of neurotransmitters — the stuff that normally helps the brain function well — that are way higher levels than they need to be.
When I teach our residents, I tell them that too much of a good thing is not actually good in this circumstance. When you have too many of the neurotransmitters we usually use for attention and memory, they actually take the system down and make it hard to function normally. That event — the neurotransmitter storm — tends to abate in the first hours to days to weeks after injury with mild or moderate or severe respectively.
Once the storm is over, it appears that some of those neurotransmitters don't simply recover to normal but actually become deficient. In combination with damage to the structures you need for memory, having not enough of the neurotransmitters to help them function is a double whammy on those systems we need to actually learn and remember information easily. So in the late period, the problem is not enough of those chemicals, as opposed to in the early period having too many of them to function normally.
Dr. David Arciniegas is a psychiatrist in Gunnison, Colorado and is affiliated with TIRR Memorial Hermann. He received his medical degree from University of Michigan Medical School and has been in practice for more than 20 years. He is one of 2 doctors at TIRR Memorial Hermann who specialize in Psychiatry.