Testing the neural noise hypothesis of dyslexia

Dyslexia is a specific learning disorder affecting approximately 7–12% of the population and is more commonly diagnosed in males than in females. While several cognitive and neural factors associated with dyslexia have been identified, the precise causal mechanisms underlying reading difficulties remain unclear. One recent account, the neural noise hypothesis (Hancock et al., 2017), proposes that reading difficulties arise from an imbalance between excitatory and inhibitory (E/I) processes (increased cortical excitability) leading to impairments in phonological awareness, rapid automatized naming, and multisensory integration.

I will present our studies which tested key predictions of this hypothesis. First, we examined whether low-level multisensory integration contributes to dyslexia and whether this effect is sex-specific. Next, we directly tested the neural noise hypothesis using electroencephalography (EEG) power spectrum measures and concentrations of Glutamate (Glu) and GABA obtained with magnetic resonance spectroscopy (MRS) at 7T.

Only males with dyslexia exhibited deficits in multisensory integration of simple, non-linguistic stimuli, as assessed by a reaction time task. However, EEG and MRS results, supported by Bayesian analyses, provided no evidence for differences in E/I balance between groups, challenging the hypothesis that cortical hyperexcitability underlies dyslexia.

Bio

Katarzyna Jednoróg is a professor of cognitive neuroscience and head of the Laboratory of Language Neurobiology at the Nencki Institute of Experimental Biology, Polish Academy of Sciences in Warsaw. Her research focuses on the neurobiological basis of language and reading development in both typical and atypical populations, with a particular emphasis on developmental dyslexia. She investigates how brain structure and function support literacy acquisition, using non-invasive neuroimaging methods such as EEG, fMRI, and magnetic resonance spectroscopy.