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On the neural basis of working memory:<br/>How the brain retains information in the face of distraction

Final Report Summary - MEM_DISTRACTION (On the neural basis of working memory:How the brain retains information in the face of distraction.)

Summary report:
Every time you open your eyes, you are bombarded with visual information. At the same time, you need to retain previously observed information to keep track of your goals and whereabouts. When you cross the street for example, you first look left and then look right (or right first and then left when in England). When you look to the right, you have to remember what traffic was at which specific position on your left. If you would immediately forget what was on your left, you wouldn’t survive in the everyday jungle of traffic. Recent studies have shown that when you have to maintain visual information over a short delay period, the visual system in your brain keeps these visual representations active. However, when you cross the street, you do not see images of bicycles and cars floating in front of our eyes. How can your visual system both process new information and keep recently perceived information active at the same time?

The aim of the current project was to investigate which neural mechanisms are responsible for retaining visual information when processing new information. We used functional Magentic Resonance Imaging (fMRI) to determine which brain areas were active when remembering multiple items simultaneously, while discarding others. Our main finding was that when a visual working memory item is not attended, it is not represented in an active manner in visual cortex. This means that when you focus on one memory, other memories are not represented in the brain through the same neural activity, even though these unattended memories can be used instantaneously. Other mechanisms through which the brain retains this information have been proposed, such as a local, perhaps short-lived, change in the structure of neural connections. In a second study, we tried to verify these other mechanisms, however, using fMRI, we were not able to do so. This could mean that fMRI is too course of a measurement to uncover mechanisms underlying the maintenance of unattended information, since it is mainly suitable for slow events that happen over periods of seconds.

Interestingly, we did find a dissociation between memories that are unattended, but relevant for the task at hand, and memories that could be discarded from working memory. In contract to future-relevant items, the discarded memory items were actively suppressed from the visual system. This suggests that information that is no longer needed is kept from interfering with necessary information by temporarily inhibiting this information, and this manifests itself in the neural visual system.

In another, related study, we found that when distracting items are presented during a memory task that are never relevant for the task at hand, they still bias information that is maintained by the visual system. The visual system thus seems very susceptible to new input, and memories might get biased towards the new information. Indeed, behavior related to the memories was slightly biased towards the distracting information. However, higher-order visual areas that are involved in memory maintenance in a more general way were not biased due to distracting information. These findings suggest that the visual system alone is very susceptible to new input, but higher-order areas protect information such that the eventual behavior regarding memory is kept relatively stable.

In sum, we found that our neural visual system does not actively maintain all information that we keep in memory, but only the items that we focus on. Even more so, items that were first remembered, but can then be forgotten are actively suppressed. In addition, when distracting information is presented, our visual system is susceptible to this new information, while higher order areas maintain our memories in a relatively stable way. This suggests that the visual system is involved in working memory in many different ways, depending on the status of the memories we retrieve, and the intervening information.

Societal impact
Working memory is one of the most used cognitive functions in daily life. Not only when we perform relatively simple acts such as crossing a street, but especially in our professions. Imagine, for example, a highly visually demanding job such as an air traffic controller, a security doorman, or a bodyguard. The outcome of this project helps us to better understand how our working memory system deals with visual distraction and keeping information online. This gives us insight into how in visually demanding professions, information can be administered optimally. This could lead to adjustments of the systems that specialists work with as to optimize their information processing, thereby enhancing their ability to keep necessary information in mind. Another application could be the presentation of study material to children. If we know how the brain deals with distraction, school programs can be adjusted to create a better learning environment. Especially, the presentation of information to easily distracted children could be adjusted to suit their needs.