Finding a needle in a haystack may sound like a metaphor, but new research shows our brains can be electrically guided to detect targets far more quickly, even in cluttered and distracting scenes.
Published December 1, 2014 in the Proceedings of the National Academy of Sciences, this study challenges prevailing ideas about how visual attention is controlled and clarifies the roles of short-term (working) memory and long-term memory in directing attention.
“Current theories typically emphasize that working memory representations guide visual attention,” said Geoffrey Woodman, assistant professor of psychology at Vanderbilt University and co-author of the study with Ph.D. candidate Robert M.G. Reinhart. “Our results show that long-term memory can also rapidly configure attention to favor certain objects, and that modest electrical stimulation can sharply accelerate that process.”
Scientists have long known that attention can be tuned, like turning a radio dial, to favor specific visual features. What remained unclear was where and how the brain accomplishes that tuning and which memory systems provide the signals that steer attention.
To investigate, researchers applied a safe, low level of electrical current to the scalps of healthy volunteers using transcranial direct-current stimulation (tDCS). Participants performed visual search tasks in which they had to find a target object amid arrays of distracting items. Following a 20-minute session of weak electrical stimulation, volunteers found targets substantially faster, indicating a marked improvement in how attention was configured to select relevant objects.
Crucially, the team recorded participants’ brain activity while they performed the tasks to identify the neural signatures associated with the improved search performance. They looked for patterns typical of visual working memory and long-term memory. The analyses revealed that the rapid attentional enhancement was most closely linked with increased activity associated with long-term memory traces rather than the short-term working memory representations traditionally thought to drive search.
These findings suggest that long-term memory can be accessed and leveraged much more quickly than previously believed to shape attentional selection. In practical terms, information stored in long-term memory appears capable of tuning perceptual systems on the timescale necessary to guide fast search behavior. The study also demonstrates that noninvasive electrical stimulation can accelerate the use of long-term memory signals to configure attention, providing a tool for probing memory–attention interactions.
Beyond the experimental results, the work has broader implications for how researchers conceptualize the interplay between memory systems and attention. Rather than viewing working memory as the sole or dominant source of attentional templates, this research supports a model in which long-term memory provides robust, rapidly deployable templates that help the brain prioritize relevant information in complex visual scenes.
The study was supported by grants from the National Institutes of Health (R01-EY019882, P30-EY08126, F31-MH102042, and T32-EY007135) and the National Science Foundation (BCS-0957072).
Contact: Melanie Moran – Vanderbilt University
Source: Vanderbilt University press release
Image Source: The image is credited to geralt and has been released into the public domain
Original Research: Abstract for “Enhancing long-term memory with stimulation tunes visual attention in one trial” by Robert M. G. Reinhart and Geoffrey F. Woodman in PNAS. Published online January 13, 2015, doi:10.1073/pnas.1417259112