Working memory, the ability to hold things in mind and manipulate them, is very important for children and is closely linked to their success in school. For instance, limited working memory leads to difficulties with following instructions and paying attention in class (also see our previous post https://forgingconnectionsblog.wordpress.com/2015/02/05/adhd-and-low-working-memory-a-comparison/). A major research aim is to understand why some children’s working memory capacity is limited. All children start with lower working memory capacity that increases as they grow up. We also know that working memory, like all mental functions, is supported by the brain. The brain undergoes considerable growth and reorganisation as children grow up. Most studies so far looked at brain structures that support working memory across development. However, some structure may be more important in younger children and some in older children. Our new study investigates for the first time how the contribution of brain structures to working memory may change with age. For that, we tested a large number of children between 6 and 16 years on different working memory tasks. We looked at aspects of working memory concerned with storing information (locations, words) and manipulating it. The children also completed MRI scans to image their brain structure. We found that white matter connecting the two hemispheres, and white matter connecting occipital and temporal areas is more important for manipulating information held in mind in younger children, but less important in older ones. In contrast, the thickness of an area in the left posterior temporal lobe was more important in older kids. We think that these findings reflect increased specialisation of the working memory system as it develops from a distributed system in younger children that requires good wiring between different brain areas to a more localised system that is supported by high-quality local machinery. By analogy, imagine you were completing a work project. If you were collaborating with people, quality and speed are largely determined by how well the team communicates – this would be very difficult if you were trying to coordinate via mobile phones in an area with low reception. On the other hand, if one person completed the project, then the outcome would depend on the ability of this worker. The insights from this study will help us to better understand how working memory is constrained at different ages, which may allow us to design better inventions in the future to help children who struggle with working memory.
A preprint of this paper is available on BioArxiv: http://biorxiv.org/content/early/2016/08/15/069617
The analysis code is available on GitHub: https://github.com/joebathelt/WorkingMemory_and_BrainStructure_Code