by Ben Thomas
When’s the last time you forgot your cell phone? What about your anniversary? We’ve all wished for a better memory at some point. And in those moments, what we’re generally referring to are our fact-based memory systems—the ones that store experiences and learned knowledge, the ones that can be strengthened by flash cards and mnemonic devices.
But there’s another type of memory that’s equally important, though less talked about: Working memory. Working memory holds items in the current moment, like digits in a phone number or lyrics to a song. It’s the mental capability that lets you keep multiple things in mind—say, competing goals for a project at work—and navigate a solution.
And it turns out working memory is fundamental to some of our most important cognitive abilities. People with a spacious working memory are, on average, better test-takers and better students, and they have more executive control and better problem-solving skills. A strong working memory is even correlated with greater lifetime earning potential.
Until the late 1990s, many scientists thought working memory was a static quality like IQ. But in recent years, neuroscience has revealed that this core aspect of cognition can actually be bolstered with behavioral training—and the means might be as simple as an exercise in counting cards.
By Neuroskeptic, a neuroscientist who takes a skeptical look at his own field, and beyond. A different version of this post appeared on the Neuroskeptic blog.
Brain-scanning studies may be giving us a misleading picture of the brain, according to recently published findings from two teams of neuroscientists.
Both studies made use of a much larger set of data than is usual in neuroimaging studies. A typical scanning experiment might include around 20 people, each of whom performs a given task maybe a few dozen times. So when French neuroscientists Benjamin Thyreau and colleagues analysed the data from 1,326 people, they were able to increase the statistical power of their experiment by an order of magnitude. An American team led by Javier Gonzalez-Castillo, on the other hand, only had 3 people, but each one was scanned while performing the same task 500 times over.
In both cases, the researchers found that close to the whole of the brain “lit up”—that is, showed increased metabolic activity—when people were doing simple mental tasks, compared to just resting. In one case, it was seeing videos of people’s faces; in the other, it was deciding whether stimuli on the screen were letters or numbers. Both studies made use of functional magnetic resonance imaging (fMRI), which uses powerful magnetic fields to image the brain and detect the changes in blood oxygen caused by differences in the firing rate of the cells in different areas.
There have been many thousands of fMRI papers published since the technique was developed 20 years ago. The great majority of these have produced the familiar “blob” plots showing that different kinds of mental processes engage localized activity in particular parts of the brain. Thyreau and Gonzalez-Castillo, however, were able to detect effects too small to be noticed in such neuroimaging experiments, and found that rather than isolated blobs, large swathes of the brain were involved. This doesn’t mean that everywhere responded equally to the task: the signal was stronger in some areas of the brain than in others, but there were no clear-cut divisions between “active” and “inactive” areas.
While the new results don’t overturn the localization theory as such, they do show that it’s only part of the picture. The blobs are real enough, as they show us the areas where activation is strongest, but it’s misleading to think of these areas as the only places involved in a particular task. Other activations, smaller or less consistent but no less real, are hidden under the threshold of statistical noise. fMRI experiments may just be showing us the tip of the iceberg of brain activity.