Visual brain areas play vital role in short-term memory, says study
Using a new technique, researchers have found that areas of the brain involved in processing visual stimuli, and that were thought to have no role in higher cognitions, actually play an "important" part in visual working memory.
Researchers from Vanderbilt University in Nashville, Tenn., found that early visual areas — the sections of the brain that first receive and process visual signals — also store some of this information.
The researchers made the discovery using a new technique to decode results through functional magnetic resonance imaging (fMRI).
Their study is published in Thursday's edition of the journal Nature.
"We discovered that early visual areas play an important role in visual working memory," Frank Tong, co-author of the study, said in a statement. "How do people maintain an active representation of what they have just seen moments ago? This has long been a conundrum in the literature."
Researchers knew that early visual areas could process in fine detail visual signals from the eye, but thought these areas could not retain information. Conversely, research has shown that while higher-order brain areas can store information, they lack the sensitivity of the early visual areas.
Tong says the study's findings solve the mystery of how people are able to retain patterns with remarkable precision for many seconds, even without any stimulus.
Measurements of fMRI key to findings
The researchers asked study participants to observe two different orientations of striped patterns. They were then given a visual cue indicating which of the two patterns to remember. The patterns were removed, and after 11 seconds, participants were shown a third pattern and asked to describe how it was oriented in relation to the remembered pattern.
Previous research had only looked at overall brain activity during such exercises.
But throughout this experiment, an fMRI scanner observed activity patterns in four different early visual areas.
The researchers used a decoding method to determine how patterns of activity were distributed across different areas of the brain.
The researchers, looking only at these patterns measured over several trials, were able to accurately show which of the two orientation patterns a subject was asked to remember over 80 per cent of the time.
"By doing these pattern analyses, we were able to find information that was hidden before. We do not know for sure, but it's possible that a lot of information in the brain might be hidden in such activity patterns," Tong said.