PTSD can result from many different forms of traumatic exposure — for example, sexual abuse or wartime experiences. Flashbacks, which are persistent, intrusive memories of the traumatic event, are a core feature of PTSD.
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Menopause and memory: Know the facts. How to get your child to put away toys. Is a common pain reliever safe during pregnancy? Print This Page Click to Print. Free Healthbeat Signup Get the latest in health news delivered to your inbox! Sign Up. Neuroscientists often refer to this physical representation of a memory as an engram. They think that each engram has a number of synaptic connections, sometimes even in several areas of the brain, and that each neuron and synapse can be involved in multiple engrams.
How the brain forgets, by comparison, has been largely overlooked. Full stop, without exception. He was especially interested in understanding the influence of dopamine-producing neurons that connect with these structures.
Dopamine, a neurotransmitter, is involved in moderating a host of behaviours in the fly brain, and Davis proposed that this chemical messenger might also play a part in memory. Intriguingly, Davis found that dopamine is essential to forgetting 1. He and his colleagues conditioned transgenic flies to associate electric shocks with certain odours, thereby training the insects to avoid them. They then activated the dopaminergic neurons and observed that the flies quickly forgot the association.
Yet blocking the same neurons preserved the memory. Further investigation, involving a technique that enabled the researchers to monitor the activity of neurons in living flies, demonstrated that these dopamine neurons are active for long periods, at least in flies. A few years later, Hardt found something similar in rats.
He was investigating what happens at the synapses of neurons that are involved in long-term memory storage. Researchers know that memories are encoded in the mammalian brain when the strength of the connection between neurons increases. That connection strength is determined by the amount of a particular type of receptor found at the synapse.
Known as AMPA receptors, the presence of these structures must be maintained for a memory to remain intact. They are moved in and out of the synapse constantly and turn over in hours or days.
Yet some memories are still forgotten. Hardt proposed that AMPA receptors can also be removed, which suggests that forgetting is an active process. If that were true, then preventing the removal of AMPA receptors should prevent forgetting.
When Hardt and his colleagues blocked the mechanism behind AMPA-receptor removal in the hippocampi of rats, as expected, they found that the rats were prevented from forgetting the locations of objects 2. To forget certain things, it seemed that the rat brain had to proactively destroy connections at the synapse. The neurotransmitter dopamine is now known to play an essential part in memory. Paul Frankland, a neuroscientist at the Hospital for Sick Children in Toronto, Canada, had also found evidence that the brain is wired to forget.
Frankland was studying the production of new neurons, or neurogenesis, in adult mice. The process had long been known to occur in the brains of young animals, but had been discovered in the hippocampi of mature animals only about 20 years earlier.
Because the hippocampus is involved in memory formation, Frankland and his team wondered whether increasing neurogenesis in adult mice could help the rodents to remember. As contradictory as that initially seemed to Frankland, given the assumption that new neurons would mean more capacity for and potentially better memory, he says it now makes sense. Because the hippocampus is not where long-term memories are stored in the brain, its dynamic nature is not a flaw but a feature, Frankland says — something that evolved to aid learning.
The environment is changing constantly and, to survive, animals must adapt to new situations. Allowing fresh information to overwrite the old helps them to achieve that. Researchers think that the human brain might operate in a similar way. Studies of people with exceptional autobiographical memories or with impaired ones seem to bear this out. People with a condition known as highly superior autobiographical memory HSAM remember their lives in such incredible detail that they can describe the outfit that they were wearing on any particular day.
Those with severely deficient autobiographical memory SDAM , however, are unable to vividly recall specific events in their lives. As a result, they also have trouble imagining what might happen in the future. They can study these images and look for signs of Alzheimer disease. When a person is diagnosed with Alzheimer disease, the doctor may prescribe medicine to help with memory and thinking.
The doctor also might give the person medicine for other problems, such as depression sad feelings that last a long time. Unfortunately, the medicines that the doctors have can't cure Alzheimer disease; they just help slow it down. You might feel sad or angry — or both — if someone you love has Alzheimer disease.
You might feel nervous around the person, especially if he or she is having trouble remembering important things or can no longer take care of himself or herself. You might not want to go visit the person, even though your mom or dad wants you to. You are definitely not alone in these feelings. Try talking with a parent or another trusted adult. Just saying what's on your mind might help you feel better.
You also may learn that the adults in your life are having struggles of their own with the situation. If you visit a loved one who has Alzheimer disease, try to be patient. He or she may have good days and bad days. It can be sad if you can't have fun in the same ways together. Maybe you and your grandmother liked to go to concerts. If that's no longer possible, maybe bring her some wonderful music and listen together.
It's a way to show her that you care — and showing that love is important, even if her memory is failing. Reviewed by: Steven Dowshen, MD.
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