Poor Short Term Memory Linked to Inability to Ignore Distractions

A new study by Simon Fraser University researchers has found that differences in an individual’s working memory capacity correlate with the brain’s ability to actively ignore distraction.

Their study was published this week in the journal PNAS.

Psychology professor John McDonald and doctoral student John Gaspar led the research team.

They used electroencephalogram (EEG) technology, which detects electrical activity in the brain, to study memory and distraction.

They found that individuals who perform well on memory tasks were able to suppress distractions. Those who didn’t perform as well couldn’t suppress distractions quickly enough to prevent them from grabbing their attention.

“Distraction is a leading cause of injury and death in driving and other high-stake environments, and has been associated with attentional deficits, so these results have important implications,” says McDonald, who holds a Canada Research Chair in Cognitive Neuroscience.

Researchers measured participants’ visual working memory limit by having them complete change-detection tasks.

“In this task, an individual is shown a series of coloured boxes for less than a second and must remember as many boxes as they can. The better they perform on this task, the higher their working memory capacity is (i.e. the more they can remember).

To study the neural processes related to suppression, researchers recorded electrical brain signals from electrodes placed on participants’ heads. Using this EEG technology they tracked the neural processing of relevant and irrelevant visual objects while individuals performed attention-demanding visual search tasks.

Image shows the research putting an EEG cap on a test subject.
John Gaspar, an SFU psychology doctoral student, places 128 electrodes into a cap. The electrodes will pick up tiny changes in the wearer’s brain activity. Image is adapted from the SFU press release.

From these, they examined participants’ working memory capacity score with respect to their electrical brain signals, to see if a relationship existed.

After examining these memory processes, researchers are now interested in what other processes and behaviours might be associated with these visual-search brain mechanisms, particularly the suppressive mechanism, says Gaspar.

“For example, how do individuals with attention-hyperactivity deficit disorder, individuals who have suffered from a concussion, or anxious individuals differ in their ability to pay attention? “Ultimately, we hope that our discoveries will enable scientists and health care professionals to understand, identify and help individuals with distraction-related attentional deficits.”

The study is linked to two previous papers in 2009 and 2014, in which McDonald’s research team showed that when people search the visual world for a particular object, the brain has distinct mechanisms for both locking attention onto relevant information and for suppressing irrelevant information.

The study is the first to relate these specific visual-search mechanisms to memory and show that the suppression mechanism is absent in individuals with low memory capacity.

About this memory research

Also on the research team: SFU PhD student Greg Christie, former SFU post-doc David Prime (now at Douglas College) and professor Pierre Jolicoeur, Canada Research Chair in Experimental Cognitive Science, University of Montreal.

Funding: The Natural Sciences and Engineering Research Council (NSERC) funded the research.

Source: Simon Fraser University
Image Credit: Image is adapted from the Simon Fraser University press release.
Original Research: Abstract for “Inability to suppress salient distractors predicts low visual working memory capacity” by John M. Gaspar, Gregory J. Christie, David J. Prime, Pierre Jolicoeur, and John J. McDonald in PNAS. Published online February 22 2016 doi:10.1073/pnas.1523471113


Inability to suppress salient distractors predicts low visual working memory capacity

According to contemporary accounts of visual working memory (vWM), the ability to efficiently filter relevant from irrelevant information contributes to an individual’s overall vWM capacity. Although there is mounting evidence for this hypothesis, very little is known about the precise filtering mechanism responsible for controlling access to vWM and for differentiating low- and high-capacity individuals. Theoretically, the inefficient filtering observed in low-capacity individuals might be specifically linked to problems enhancing relevant items, suppressing irrelevant items, or both. To find out, we recorded neurophysiological activity associated with attentional selection and active suppression during a competitive visual search task. We show that high-capacity individuals actively suppress salient distractors, whereas low-capacity individuals are unable to suppress salient distractors in time to prevent those items from capturing attention. These results demonstrate that individual differences in vWM capacity are associated with the timing of a specific attentional control operation that suppresses processing of salient but irrelevant visual objects and restricts their access to higher stages of visual processing.

“Inability to suppress salient distractors predicts low visual working memory capacity” by John M. Gaspar, Gregory J. Christie, David J. Prime, Pierre Jolicoeur, and John J. McDonald in PNAS. Published online February 22 2016 doi:10.1073/pnas.1523471113

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