fMRI decoding finds echoes of working memory

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A new technique for decoding data from functional MRI (fMRI) could be used to discover early visual areas, which play an important role is visual working memory, according to research published online this month in the journal  Nature.

The findings are a significant step forward in understanding how we perceive, process and remember visual information, according to the authors.

"We discovered that early visual areas play an important role in visual working memory," said co-author of the research Frank Tong, an associate professor of psychology at Vanderbilt Univeristy in Nashville, Tenn. He said that understanding how people maintain an active representation of what they have just seen moments ago has long been a conundrum.

Using a new technique to analyze fMRI data, the researchers found that the fine-scale activity patterns in early visual areas reveal a trace, or something like an echo, of the stimulus that the person is actively retaining, even though the overall activity in these areas is really weak after the stimulus is removed, Tong said.

"By using a neural decoding technique, we were able to read out what people were holding in their visual memory. We believe this sustained visual information could be useful when people must perform complex visual tasks in everyday life," said lead author Stephenie Harrison, a graduate student in the Vanderbilt psychology department.

Research subjects were shown two examples of simple striped patterns at different orientations. They were then told to hold either one or the other of the orientations in their mind while being scanned using fMRI.

"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. "Using this decoding technique and others, neuroscientists might get a better understanding of how the brain represents specific cognitive states involving memory, reminiscing, or other visual experiences that do not obviously lead to a huge amount of activity in the visual areas."

The National Eye Institute, the National Institutes of Health and the Natural Sciences and Engineering Research Council of Canada provided funding for the study.