1. Neuroscience

Dyslexics' faster decay of implicit memory for sounds and words is manifested in their shorter neural adaptation

  1. Sagi Jaffe-Dax  Is a corresponding author
  2. Orr Frenkel
  3. Merav Ahissar  Is a corresponding author
  1. The Hebrew University of Jerusalem, Israel
https://doi.org/10.7554/eLife.20557
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  1. Sagi Jaffe-Dax
  2. Orr Frenkel
  3. Merav Ahissar
(2017)
Dyslexics' faster decay of implicit memory for sounds and words is manifested in their shorter neural adaptation
eLife 6:e20557.
https://doi.org/10.7554/eLife.20557
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Abstract

Dyslexia is a prevalent reading disability whose underlying mechanisms are still disputed. We studied the neural mechanisms underlying dyslexia using a simple frequency-discrimination task. Though participants were asked to compare the two tones in each trial, implicit memory of previous trials affected their responses. We hypothesized that implicit memory decays faster among dyslexics. We tested this by increasing the temporal intervals between consecutive trials, and measuring the behavioral impact and ERP responses from the auditory cortex. Dyslexics showed a faster decay of implicit memory effects on both measures, with similar time constants. Finally, faster decay also characterized dyslexics' benefits in oral reading rate. It decreased faster as a function of the time interval from the previous reading of the same non-word. We propose that dyslexics' shorter neural adaptation paradoxically accounts for their longer reading times, since it induces noisier and less reliable predictions for both simple and complex stimuli.

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Author details

  1. Sagi Jaffe-Dax

    Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
    For correspondence
    sagi.jaffe@mail.huji.ac.il
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8759-6980

  2. Orr Frenkel

    Psychology Department, The Hebrew University of Jerusalem, Jerusalem, Israel
    Competing interests
    The authors declare that no competing interests exist.

  3. Merav Ahissar

    Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
    For correspondence
    msmerava@gmail.com
    Competing interests
    The authors declare that no competing interests exist.

Funding

Israel Science Foundation (616/11)

  • Merav Ahissar

Israel Science Foundation (2425/15)

  • Merav Ahissar

Gatsby Charitable Foundation

  • Merav Ahissar

EPFL-HUJI collaboration

  • Merav Ahissar

German-Israeli Foundation for Scientific Research and Development (I-1303-105.4/2015)

  • Merav Ahissar

Canadian Institutes of Health Research

  • Merav Ahissar

International Development Research Centre

  • Merav Ahissar

Azrieli Foundation

  • Merav Ahissar

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Human subjects: Informed consent was acquired from all participants. The study was approved by The Hebrew University Committee for the Use of Human Subject in Research.

Copyright

© 2017, Jaffe-Dax et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Sagi Jaffe-Dax
  2. Orr Frenkel
  3. Merav Ahissar
(2017)
Dyslexics' faster decay of implicit memory for sounds and words is manifested in their shorter neural adaptation
eLife 6:e20557.
https://doi.org/10.7554/eLife.20557

Share this article

https://doi.org/10.7554/eLife.20557

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Further reading

    1. Neuroscience

    Shorter cortical adaptation in dyslexia is broadly distributed in the superior temporal lobe and includes the primary auditory cortex

    Sagi Jaffe-Dax, Eva Kimel, Merav Ahissar
    Research Advance Updated

    Studies of the performance of individuals with dyslexia in perceptual tasks suggest that their implicit inference of sound statistics is impaired. Previously, using two-tone frequency discrimination, we found that the effect of previous trials' frequencies on the judgments of individuals with dyslexia decays faster than the effect on controls' judgments, and that the adaptation (decrease of neural response to repeated stimuli) of their ERP responses to tones is shorter (Jaffe-Dax et al., 2017). Here, we show the cortical distribution of these abnormal dynamics of adaptation using fast-acquisition fMRI. We find that faster decay of adaptation in dyslexia is widespread, although the most significant effects are found in the left superior temporal lobe, including the auditory cortex. This broad distribution suggests that the faster decay of implicit memory of individuals with dyslexia is a general characteristic of their cortical dynamics, which also affects sensory cortices.