An Irrelevancy Filter? Differences Correlated Brain Activity Images with Working Memory Capacity and Ability to Ignore Distractions

The ability to hold and use information in the mind for immediate access is known as “working memory.” Examples are remembering numbers for math calculations or for dialing a telephone number. Working memory also involves holding information while other relevant tasks are performed. Working memory capacity varies from person to person. A recent study by Dr Torkel Klingberg and Fiona McNab at the Stockholm Brain Institut, Karolinska Institutet found that a good working memory capacity may not be attributed to having larger memory storage, but to having a better filter that keeps out irrelevant information.

The study involved functional magnetic resonance imaging (fMRI) of 25 healthy volunteers that performed a computer-based task that focused on visual images with or without irrelevant distractions. A noise alerted test subjects that irrelevant information was about to be presented.

The subject’s brains (specifically the prefrontal cortex and the basal ganglia) responded to the sound ahead of the distractions. The fMRI showed greater activity in the globus pallidus located in the basal ganglia that correlated with less unnecessary storage in the posterior parietal cortex— an area of the brain related to the amount of information held in memory. The preceding frontal and basal ganglia activity was correlated with inter-individual differences in working memory capacity of the test subjects.

The scientists had the intent of investigating attention deficit hyperactivity disorder (ADHD) in children.

McNab F, Klingberg T. Prefrontal cortex and basal ganglia control access to working memory. Nat Neurosci. 2007 Dec 9; [Epub ahead of print]

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