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William Schmitt, Hrag Pailian, George A. Alvarez; Using Neurostimulation to Augment the Encoding of Information in Visual Working Memory. Journal of Vision 2020;20(11):166. doi: https://doi.org/10.1167/jov.20.11.166.
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Storage limits in visual working memory (VWM) impose an information-processing bottleneck, restricting input to broader cognition. Our capacity to store random, uncorrelated input is extremely limited (e.g., ~3 colors), but previous work has shown that more content can be stored if there are statistical regularities in the input (e.g., if pairs of colors tend to co-occur; Brady, Konkle, and Alvarez, 2009). Here, we used a novel non-invasive brain stimulation technique, trans-cranial random noise stimulation (tRNS), to enhance the learning of these regularities and consequently increase the amount of information retained in VWM. We presented three separate groups of participants with displays consisting of 8 colored circles, arranged in 4 concentric pairs. The colors disappeared, after which participants reported the identity of a cued circle by choosing from the 8 possible color-options. Participants in the “tRNS+Pattern” group received 20-minutes of neurostimulation to the right posterior parietal and right dorsolateral prefrontal cortices during the first 20-minutes of testing, and were also presented with displays containing regularities (i.e. 4 pairs of colors appeared together 80% of the time). Though the remaining groups of participants were connected to the neurostimulator, they did not receive stimulation. For these sham stimulation conditions, members of the “no tRNS-Pattern” group were also presented with displays with the same regularities, whereas color combinations for the “no tRNS-Uniform” group were sampled from a uniform distribution. Replicating the effects observed by Brady et al. (2009), “no tRNS-Pattern” participants were able to store more items in memory, relative to their “no tRNS-Uniform” counterparts. Critically, neuroenhancement effects were observed, such that members of the “tRNS+Pattern” group demonstrated the most superior performance. Performance across all groups plummeted to comparable levels when regularities were removed, reaffirming that the observed benefits reflect enhanced encoding. Neurostimulation may prove instrumental towards augmenting VWM and broader cognition.
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