Our ability to forget may be just as important as our ability to remember.
We may want to forget woes and traumas, but it may be even more useful to unburden ourselves of the trivial—the mental minutia and impedimenta that accumulates in the course of ordinary existence.
Stanford University researchers using functional magnetic resonance imaging (fMRI) were able to record visual images of people’s brains as they discarded irrelevant memories in order to focus on the task of learning something new.
Brice Kuhl, a doctoral student working in the Stanford Memory Lab
run by Associate Professor Anthony Wagner explains that the brain is very plastic and adaptive and that means that it suppresses or weakens some memories at the same time it strengthens others. "Remembering something actually has a cost for memories that are related but irrelevant,” he explains in a Stanford Report
Kuhl and Wagner, both neuroscientists, gathered 20 Stanford students between the ages of 18 and 32 and had them view 240 pairs of words in rapid succession while their brains were being scanned. The word list included 40 words printed in capitals. Each of the 40 capitalized word was paired separately with six words printed in lower case letters—for instance ATTIC-junk and ATTIC-dust. So there were six memories created for each main word. After viewing all words, subjects were asked to try to remember selected pairs. The first time they practiced a pair, the story explains, the prefrontal cortex "lit up” as the brain worked to forge a new memory from among the competing pairs. In their second and third memory practices, the frontal lobes became less active. The more the frontal lobe activity decreased, the more likely it was that in later testing the participant would remember the selected pairs and not the irrelevant ones.
Wagner says the prefrontal cortex is the "CEO of the brain,” governing cognition and the purposeful uses of memories. When unimportant memories are suppressed, he says, the brain can devote more of its computational resources to recalling what’s important.
The findings by Kuhl and Wagner were published in the June 3 issue of Nature Neuroscience and are also the subject of a New York Times story by Benedict Carey
. Their work may have implication for treating difficulties associated with aging and neurological diseases.
In similar research last year at the University of California at Berkeley
, neuroscientists Adam Gazzaley and Mark D’Esposito
found that memory losses associated with aging resulted more from distractions than from an inability to focus. These researchers, who also tested their subjects while their heads were in an fMRI scanner, discovered that many older people are able to focus on pertinent information, but that their reduced ability to screen out the distractions and irrelevant information resulted in impaired memory. Their work suggests people with Alzheimer’s disease and other age-related memory problems may benefit more from drugs targeting the suppression of distraction than from drugs that enhance focus.
The poet Robert Pinsky
, who has reflected philosophically and lyrically on the power of things lost, remembered and disregarded, reminds us "Forgetting is never perfect, just as recall is never total: the list or the person’s name, or the poem or the phone number may be recalled in every detail, but never with the exact feeling it had. And conversely, the details may be obliterated, but a feeling lingers on. .…memory and forgetting are willful and involuntary, helpless and desperate in mysterious measures. Forgetting is not mere absence. The repressed does not merely return, it transforms and abrogates, rising and plunging like a dolphin or Proteus.” And what about the colorless memories that are merely suppressed? The Times story suggests they may just get lost in a sensory crowd.