Archive for January 9th, 2012
Forming and storing a memory is a multistep process that involves several parts of the brain. A memory is not a single entity, like a book on a shelf. Instead, memory is the aggregation of multiple streams of sensory information, filtered through the perception of the person observing or participating in the event. Each of the different components of memory is stored and processed in a different region of the brain.
Because memory storage and retrieval is so complex, even healthy people can experience memory loss or memory distortion from time to time. Dr. Daniel Schacter, a professor of psychology at Harvard University, has identified seven common “sins” of memory. Some of these memory flaws become more pronounced with age, but — unless they are extreme and persistent — they are not considered indicators of Alzheimer’s disease or other memory-impairing illnesses.
Memory has a use-it-or-lose-it quality. People are most likely to retain memories that they call up and use frequently. Those memories that are not retrieved as frequently tend to fade away.
Transience is the term scientists use to describe the tendency to forget some facts or events over time. Although transience might seem like a sign of memory weakness, brain scientists regard it as beneficial because it clears the brain of unused memories, making way for newer, more useful ones.
Everyone experiences transience of memory. For example, people are most likely to forget information soon after they learn it — particularly if they don’t need it again (such as memorizing a phone number used only once or twice).
This type of forgetting occurs when people don’t pay close enough attention to something. Someone might forget where he just put a pen because he didn’t focus on where he put it in the first place. He was thinking of something else (or, perhaps, nothing in particular), so his brain didn’t encode the information securely. Absentmindedness also involves forgetting to do something at a prescribed time, like taking medicine or keeping an appointment.
One way people can avoid this problem is to identify things that can serve as cues to remind them to do something. For example, if the doctor says to take a medicine at bedtime, an individual might use another regular bedtime activity as a reminder cue. In this situation, for example, a woman could mentally link brushing her teeth with taking a medicine. Similarly, if a man needs to take vitamins at breakfast, he could make a habit of putting the bottle beside his coffee cup at the table so it provides a cue when he sits down to eat.
This refers to the experience in which the answer is right on the tip of your tongue — but you just can’t think of it. This tip-of-the-tongue experience is perhaps the most familiar example of blocking, the temporary inability to retrieve a memory. Blocking doesn’t occur because you aren’t paying attention or because the memory has faded away. On the contrary, blocking occurs when a memory is properly stored in your brain, but something is keeping you from retrieving it.
In many cases, people retrieve the wrong memory — one that is similar to the desired one. This competing memory is so intrusive that they can’t think of the memory they want. A common example is a mother who calls her older son by a younger son’s name, or vice versa. Scientists call blocking memories “ugly stepsisters” because they’re domineering, like the stepsisters in Cinderella.
Brain-imaging studies suggest how blocking might occur. When a person is retrieving a memory, some regions of the brain become more active while others simultaneously become less active. When the right regions are activated, this can work in an individual’s favor by keeping the brain from calling up irrelevant information. But when the individual calls up an ugly stepsister by mistake, the brain may simultaneously suppress the regions needed to retrieve the desired memory.
Researchers do not know whether memory blocks reflect the overall slowing of memory retrieval that occurs with age or if they occur for some other reason. In any case, there’s encouraging news: research shows that people are able to retrieve about half of blocked memories within minutes.
Consider the following scenario: An individual remembers quite clearly who John Smith is and what he’s done lately that’s been newsworthy. When someone asks the source of these details, the individual thinks for a moment and replies that it was on the evening TV news. As it turns out, however, he got his information from a friend over lunch.
Right memory, wrong source — that’s one example of misattribution. Misattribution occurs when a person remembers something accurately in part, but misattributes some detail, like the time, place, or person involved. Another kind of misattribution occurs when someone believes a thought she had was totally original when, in fact, it came from something she had previously read or heard but had forgotten about. This sort of misattribution explains cases of unintentional plagiarism, in which a writer presents some information as original when he or she actually read it somewhere before.
Misattribution happens to everyone. Usually it’s harmless, but it can have profound consequences, particularly in the criminal justice system. In some cases, misattribution on the part of eyewitnesses is responsible for the arrest and conviction of individuals for crimes they didn’t commit.
As with several other kinds of memory lapses, misattribution becomes more common with age. Age matters in at least two ways. First, as people age, they absorb fewer details when acquiring information because they have somewhat more trouble concentrating and processing information rapidly. Second, as they grow older, their memories grow older as well. And old memories are especially prone to misattribution.
Suggestibility is the vulnerability of memory to the power of suggestion — information that people learn about an occurrence after the fact. Although little is known about exactly how suggestibility works in the brain, the suggestion somehow fools the person into thinking it’s a real memory. Suggestibility can be the culprit in recollections that adults have of incidents from their childhood that never really happened.
Critics of “recovered memories” — a concept popularized during the child sexual abuse scandals of the 1980s and 1990s — say that therapists in particular can contribute to suggestibility. Research indicates that suggestion is most effective when it comes from a person designated as a healer and authority. Insistent leading questions are especially dangerous, but even a therapist who is trying to be neutral may convey a bias. Hypnosis and guided imagery, commonly used by recovered memory therapists, blur the line between imagination and reality and greatly heighten confidence in memories while lowering their accuracy. The problem becomes magnified when people are asked to imagine something repeatedly, until it seems familiar, and then talk about it as though it were real.
One of the enduring myths about memory is that it works like a camera, recording what people perceive and experience with complete, objective accuracy. But even the sharpest memory is not a flawless snapshot of reality. In any individual’s memory, perceptions are filtered by personal biases — experiences, beliefs, knowledge, and even mood at the moment. These biases come into play when experiences are being encoded in the brain. And when people retrieve a memory, their mood and other biases at that moment can influence what information they actually recall.
Bias can affect all sorts of memories, but among the most interesting examples are people’s recollections of their romantic relationships. In one study, couples who were dating were asked to evaluate themselves, their partners, and their relationships — during a first interview and then two months later. During the second session, participants were asked to recall what they had said initially. The people whose feelings for their partners and their relationships had become more negative over time recalled their first evaluations as more negative than they really had been. On the other hand, people whose feelings for their partners and their relationships had become more loving recalled their first impressions as more positive than they really had been.
Most people worry about forgetting things. But in some cases people are tormented by memories they wish they could forget, but can’t. The persistence of memories of traumatic events, negative feelings, and ongoing fears is another form of memory problem. Some of these memories accurately reflect horrifying events, while others may be negative distortions of reality.
Two groups of people are particularly prone to having persistent, disturbing memories — those with depression and those with post-traumatic stress disorder (PTSD).
Research has shown that depressed people are given to ruminating over unpleasant events in their lives or mistakes that they believe they have made. Dwelling on such negatives also fuels a vicious cycle of increasing depression.
Those with PTSD have persistent, unwanted memories. This disorder 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.
When to seek help
If people become concerned about whether their memory lapses are normal, it may be time to consult a doctor. Some memory problems are caused by medical disorders and respond to treatment. For instance, people with depression or high blood pressure often find that treating those conditions restores their memory function or at least prevents further decline. On the other hand, a normal exam can provide peace of mind.Read Full Post | Make a Comment ( None so far )