How The Brain Works: Visual Working Memory

Scientists from Cardiff University in Wales, have contributed a new and important piece of information to our understanding of working memory processing — specifically visual working memory. Unlike image recognition (known as encoding) which activates specific brain regions depending on the type of image, the short term storage of images in working memory involves more generalized brain activation.

David E. J. Linden, Nikolaas N. Oosterhof, Christoph Klein, and, Paul E. Downing detailed their findings in the Journal of Neurophysiology.

Using fMRI (real time brain imaging) the researchers had eighteen participants view and memorize three sequentially presented images from one of four categories: faces, bodies, scenes, or flowers.

Ten seconds later they displayed an image from the same category and asked the participants to indicate whether this new image matched one of the previous three images–a test of visual working memory.  The test was repeated eighty times (with twenty iterations for each of the four categories). The researchers addressed the possibility that the participants were remembering the images as words rather than pictures they played the radio as background noise during the entirety of the experiment.

Region Activated for Working Memory Storage

The fMRI data showed that the brain areas known to be activated during visualization (encoding) at the rear of the brain declined in activity during the 10 second delay. Whereas areas near the front of the brain–in the prefrontal cortex and medial frontal gyrus–became active during the long delay while the participants tried to hold the images in working memory.

The same frontal areas activated during the working memory test for all visual stimuli, regardless of the category, suggesting they activate in a more general pattern for visual working memory with no particular specialization based on image category.

“We conclude that principles of cortical activation differ between encoding and maintenance of visual material,” the authors said.

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