Working memory (WM) is a cognitive system which has a limited capacity and can temporarily hold information. This system is vital in our reasoning, behaviour and decision making. Due to its limited capacity, the removal of irrelevant information is crucial in this system. Loss of this function can lead to a variety of psychiatric disorders such as post-traumatic stress disorder (PTSD) obsessive-compulsive disorder (OCD), depression, and anxiety. Researching the ways in which we remove thoughts from our minds has proven difficult. Therefore, researchers at the University of Colorado Boulder and the University of Texas conducted a study using both machine learning (a form of artificial intelligence which allows self-learning from data and the application of this learning without human intervention) and brain imaging, to learn what happens when we try to remove information from our minds. This is useful in providing new information about our cognition and in creating new approaches in treating some psychiatric disorders.
Data was collected from a total of 258 participants (with normal vision, no brain injury and no psychiatric or neurological disorder). They participated in a fMRI study and a behavioural study. In the fMRI study, pictures from three categories and three subcategories were shown to 50 of the total participants. These categories and subcategories were faces (actor, musician, and politician), scenes (beach, mountain, and bridge) and finally fruit (apple, grape, and pear). The participants were asked to rate how desirable the pictures shown were. They were also asked with each photograph how much they would like to meet the faces shown, how much they would like to visit the scenes shown and how much they would like to eat the food shown. This allowed the researchers to characterise the brain activity pattern of participants in each category and subcategory. The participants were then asked to either maintain, replace, suppress, or clear the images shown to them. This allowed the researchers to track the status of the image in WM whilst being manipulated.
In the behavioural study, 208 participants were shown 504 images using the same categories in the fMRI study. They were divided into three categories; replace, suppress, and clear. Each group completed two blocks of trials, one their assigned group and the other a replacement of the image with the categories (e.g., replace politicians with beach).
The study showed that changing a thought or clearing the mind of all thoughts will reduce our attention on any unwanted item in our mind. This allows for there to be room in WM and allows for new learning. The results show that there are a minimum of three ways of removing information from WM, which is by replacing, suppressing, and clearing. They also show that replace and clear allowed the image to fade faster from WM, although not completely. Suppress allowed for more room in working memory, though it took longer to carry out. The results also demonstrated that the information could be temporarily or permanently removed from WM which allows for new learning.
Additionally, these results implied that the representation of an item in WM varies, depending on what the item is, which therefore affects the ways in which items may be cleared from WM. These results give an insight into the cause of some psychiatric disorders such as PTSD and OCD. Though these results give us useful ways in which to clear unwanted thoughts from our minds, it also shows how this may be ‘disadvantageous’ as seen in PTSD.
This study shows that understanding the WM may have positive implications on certain psychiatric disorders. It showed that clearing or replacing only diverts attention away from the unwanted item whereas supressing allows it to be completely removed from the mind. More research is required into how the patterns of cognition shown within those without vision problems, neurological or psychiatric disorders are impaired in those with vision problems and neurological or psychiatric disorders.
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Feature Image: Pexels, photo by Anna Shvets.
Original Source: Kim, H., Smolker, H.R., Smith, L.L. et al. Changes to information in working memory depend on distinct removal operations. Nat Commun 11, 6239 (2020). https://doi.org/10.1038/s41467-020-20085-4
Edited by Cyrus Rohani-Shukla