Brain clutter can crowd out memories, scientists suggest

‘There might also be treasure in the clutter’

Memory loss in older age may stem from the brain being too cluttered with knowledge, making it more

difficult to sift through, scientists believe.

Although forgetting names or misplacing objects may seem like a deterioration in brain function, a new theory suggests it might actually be just a slowing down caused by too much information — like an overly full hard drive.

In a new review published in the journal Trends in Cognitive Sciences, researchers at Harvard, Columbia and Toronto universities, analyzed dozens of recent neuroimaging and behavioural studies of people between 65 and 80, and came up with the new hypothesis. They propose that the brains of older adults allocate more space to accumulated knowledge and so have more material to navigate around when trying to retrieve a memory.

Neuroimaging suggests that when a younger person seeks to retrieve a memory, there is less neural baggage to slow down the process. Conversely, for older people, it takes longer because each memory is linked to more information, like trying to find a single book in a vast library of similar works.

Older people also struggle to suppress information that is no longer relevant, perhaps explaining why aging often brings the re-emergence of decades-old memories that were thought lost. It means that when searching for a specific memory, they often retrieve other, irrelevant memories and explains why it takes longer to carry out cognitive tasks, because they have to wade through previous knowledge.

In contrast, younger people can effectively shut out information that is not useful for the current task. However, although such a wealth of prior knowledge makes memory retrieval tricky, this ability of the brain to draw on a lifetime of experience does have advantages, the researchers said, making people more creative and better at problem solving and decision-making.

Studies have shown that older adults tend to do better on alternative-uses tasks, where they are asked to come

up with as many novel functions as possible for an object. It suggests prior knowledge is crucial to do well.

“There might also be treasure in the clutter,” the paper concludes. “The clutter of irrelevant information might interfere with target memory retrieval in one context, but might also provide surprising advantages in other tasks or contexts that benefit from extraneous knowledge. In these latter situations, the term ‘enriched’ might be a more appropriate descriptor of older adults’ representations than ‘cluttered.’ ”

Previous studies have suggested that memory loss in older age happens because the brain is struggling to make links, dubbed the “associative deficit hypothesis.” However the authors say both young and old people tend to score the same on associate deficit tests.

Other researchers have suggested that as people age they “outsource” memory to external factors in the environment, making internal retrieval more difficult. But the new theory suggests memory differences in old and young people are more likely linked to the inability to control excessive information.

The paper continues: “Evidence suggests that older adults show preserved, and at times enhanced, creativity as a function of enriched memories.

“In sum, although excessive information in older adults’ memory representations can interfere with the retrieval of specific target information and hurt performance, it can also provide an advantage on more open-ended tasks that benefit from extraneous knowledge.”