THINKING CAP MAPS MEMORIES.

Byline: Greg Bolt The Register-Guard

A professor at the University of Oregon for the first time has punched a tiny peephole through the wall surrounding human memory.

In a study published today in Nature magazine, cognitive psychology professor Edward Vogel describes a new technique that allows him literally to watch as the brain stores visual information in its short-term memory. What's more, Vogel is able to tell how many images of things in their surroundings people are able to stash away for immediate use and can even get a rough idea of what those memories are.

"At a very coarse level, we're kind of reading their minds," Vogel said of his breakthrough research. "It's like it opens a window to us being able to directly observe the process by which people hold things in their awareness."

Actual mind reading is unlikely at best, but Vogel's research could help understand and diagnose attention deficit disorders and provide new insight into mental illnesses such as schizophrenia. Understanding how this crucial part of memory works also could lead to new techniques to boost memory capacity or stave off the memory-robbing effects of aging.

Vogel's research centers on a particular kind of short-term memory known as visual working memory. That's a process in the brain that stores images for immediate use, helping us do things such as pick out the best apples in a bin at the grocery store or drive a car down a busy street.

It turns out that a particular type of brainwave - which Vogel discovered during research on a different topic and named contralateral delay activity, or CDA - offers a window into the process of working memory. His research showed that the level of CDA activity in a region near the back of the brain known as the posterior parietal cortex correlates with the number and type of images being stored in visual working memory.

To glimpse the memory process at work, Vogel attaches electrodes to the scalps of subjects and monitors brainwave activity using sensitive electroencephalography equipment.

Vogel's experiments involved subjects looking at a brief image on a computer screen showing varying numbers of colored squares. Then they are shown another image in which either one or none of the colors is different and are asked if anything has changed.

Previous work by Vogel and others gave an approximate idea of how many images the brain can hold onto at any given moment, but this new research allowed him to make the first precise measurement of the memory holding tank based on electrical impulses. As suspected, it's not an impressive amount.

"It turns out it's actually an incredibly small number," Vogel said. "It's like three things, on average."

Of course, people perceive a vivid image of the world around them. But even though our visual system sees a wealth of detail, very little of it is saved; it seems that once something leaves our field of vision, it pretty much ceases to exist as far as the brain is concerned.

The amount of visual working memory varies from person to person, with some storing only one or two images and a few able to handle six or seven. But people reach their memory capacity relatively quickly, and beyond that their ability to reconstruct an event or image is no more accurate than guessing, Vogel said.

But his experiments did more than measure the size of working memory. Vogel also got a real-time look at brain activity as memories were created and was able to tell something about what was being remembered.

For example, Vogel could tell whether the objects going into working memory were located on the right side of the computer screen or the left side based on the level and location of CDA activity measured at the scalp. Vogel hopes that future research will reveal even more about the images going into the brain's short-term filing system, such as whether it's an image of a face or a car or something else.

"Currently we don't really know whether we'll be able to distinguish between those kinds of things, but that's something we're trying to find out," he said.

"I doubt that it would get that really detailed, but you never know."

Vogel is also moving ahead with research on the role of CDA activity in schizophrenics. He said current studies suggest people suffering from the illness may have a hard time selecting essential details for storage in working memory, making it difficult for them to make sense of a complex environment.

A similar problem could face children and adults with attention deficit problems. Difficulty concentrating on a single task could be related to an inability to store information in short-term memory.

"This gives us a really powerful new tool to study lots of things," Vogel said.

CAPTION(S):

Tommy Selling reacts in mock surprise as gel is added to an electrode skull cap being used to plot his brain waves at the University of Oregon.