Pinging the brain to reveal hidden memories

Abstract

Keeping a picture in mind requires many brain cells to actively communicate … or does it? There might be more to working memory than neuronal chatter, and silent processes could be hiding right beneath the surface.

Figure 1

How to ping a brain. Summary of the first experiment by Wolff et al.. Top: participants see two striped circles to keep in working memory (left), activating a sensory-related brain network (yellow nodes). Bottom: the information graph is color-coded to match the colored rings outlining the striped circles in the top panel and shows how much information was present for each. (Colored rings were not visible during the actual experiment.) Right after the two orientations are shown, information can be read out from the recorded brain activity equally well for both orientations. As the working memory delay progresses (top middle), the amount of information fizzles out. After about a second, an arrow tells participants which orientation they will need to recall later. Here the arrow points to the right side of the screen, which means that the orientation previously shown on the left is now irrelevant. When the ping appears another second later (right), information reemerges from the neural signal for the orientation with continued relevance but not the irrelevant orientation. The information pattern after the ping (right; yellow nodes) differs fundamentally from the pattern at the time when the orientations were actually perceived.