Journal
HUMAN BRAIN MAPPING
Volume 37, Issue 8, Pages 2767-2783Publisher
WILEY
DOI: 10.1002/hbm.23206
Keywords
auditory entrainment; effective connectivity; developmental dislexia; magnetoencephalography; speech perception
Funding
- Spanish Ministry of Science and Innovation [CONSOLIDER-INGENIO2010 CSD2008-00048, PSI2012-31448]
- European Commission 7th Framework Programme [AThEME]
- European Research Council [ERC-2011-ADG-295362]
- Spanish Ministry of Economy and Competitiveness [PSI2012-32350, PSI2015-65694-P, PSI2012-32128]
- Award Centro de Excelencia Severo Ochoa [SEV-2015-0490]
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Developmental dyslexia is a reading disorder often characterized by reduced awareness of speech units. Whether the neural source of this phonological disorder in dyslexic readers results from the malfunctioning of the primary auditory system or damaged feedback communication between higher-order phonological regions (i.e., left inferior frontal regions) and the auditory cortex is still under dispute. Here we recorded magnetoencephalographic (MEG) signals from 20 dyslexic readers and 20 age-matched controls while they were listening to similar to 10-s-long spoken sentences. Compared to controls, dyslexic readers had (1) an impaired neural entrainment to speech in the delta band (0.5-1 Hz); (2) a reduced delta synchronization in both the right auditory cortex and the left inferior frontal gyrus; and (3) an impaired feedforward functional coupling between neural oscillations in the right auditory cortex and the left inferior frontal regions. This shows that during speech listening, individuals with developmental dyslexia present reduced neural synchrony to low-frequency speech oscillations in primary auditory regions that hinders higher-order speech processing steps. The present findings, thus, strengthen proposals assuming that improper low-frequency acoustic entrainment affects speech sampling. This low speech-brain synchronization has the strong potential to cause severe consequences for both phonological and reading skills. Interestingly, the reduced speech-brain synchronization in dyslexic readers compared to normal readers (and its higher-order consequences across the speech processing network) appears preserved through the development from childhood to adulthood. Thus, the evaluation of speech-brain synchronization could possibly serve as a diagnostic tool for early detection of children at risk of dyslexia. (C) 2016 Wiley Periodicals, Inc.
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