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Front. Hum. Neurosci. | doi: 10.3389/fnhum.2018.00109

Parietotemporal stimulation affects acquisition of novel grapheme-phoneme mappings in adult readers

  • 1Communication Sciences and Disorders, University of Texas at Austin, United States
  • 2Department of Psychology and Human Development, Vanderbilt University, United States

Neuroimaging work from developmental and reading intervention research has suggested a cause of reading failure may be lack of engagement of parietotemporal cortex during initial acquisition of grapheme-phoneme (letter-sound) mappings. Parietotemporal activation increases following grapheme-phoneme learning and successful reading intervention. Further, stimulation of parietotemporal cortex improves reading skill in lower ability adults. However, it is unclear whether these improvements following stimulation are due to enhanced grapheme-phoneme mapping abilities. To test this hypothesis, we used transcranial direct current stimulation (tDCS) to manipulate parietotemporal function in adult readers as they learned a novel artificial orthography with new grapheme-phoneme mappings. Participants received real or sham stimulation to the left inferior parietal lobe for twenty minutes before training. They received explicit training over the course of three days on ten novel words each day. Learning of the artificial orthography was assessed at a pre-training baseline session, the end of each of the three training sessions, an immediate post-training session, and a delayed post-training session about four weeks after training. Stimulation interacted with baseline reading skill to affect learning of trained words and transfer to untrained words. Lower skill readers showed better acquisition, whereas higher skill readers showed worse acquisition, when training was paired with real stimulation, as compared to readers who received sham stimulation. However, readers of all skill levels showed better maintenance of trained material following parietotemporal stimulation, indicating a differential effect of stimulation on initial learning and consolidation. Overall, these results indicate that parietotemporal stimulation can enhance learning of new grapheme-phoneme relationships in readers with lower reading skill. Yet, while parietotemporal function is critical to new learning, its role in continued reading improvement likely changes as readers progress in skill.

Keywords: transcranial direct current stimulation, parietotemporal cortex, reading acquisition, Artificial orthography, reading skill

Received: 03 Jan 2018; Accepted: 06 Mar 2018.

Edited by:

Silvia Brem, Psychiatrische Klinik der Universität Zürich, Switzerland

Reviewed by:

Fabio Richlan, University of Salzburg, Austria
Kristina Moll, Ludwig-Maximilians-Universität München, Germany  

Copyright: © 2018 Younger and Booth. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mrs. Jessica W. Younger, University of Texas at Austin, Communication Sciences and Disorders, Austin, Texas, United States,