Is there evidence for a noisy computation deficit in developmental dyslexia?

Abstract

The noisy computation hypothesis of developmental dyslexia (DD) is particularly appealing because it can explain deficits across a variety of domains, such as temporal, auditory, phonological, visual and attentional processes. A key prediction is that noisy computations lead to more variable and less stable word representations. A way to test this hypothesis is through repetition of words, that is, when there is noise in the system, the neural signature of repeated stimuli should be more variable. The hypothesis was tested in an functional magnetic resonance imaging experiment with dyslexic and typical readers by repeating words twelve times. Variability measures were computed both at the behavioral and neural levels. At the behavioral level, we compared the standard deviation of reaction time distributions of repeated words. At the neural level, in addition to standard univariate analyses and measures of intra-item variability, we also used multivariate pattern analyses (representational similarity and classification) to find out whether there was evidence for noisier representations in dyslexic readers compared to typical readers. Results showed that there were no significant differences between the two groups in any of the analyses despite robust results within each group (i.e., high representational similarity between repeated words, good classification of words vs. non-words). In summary, there was no evidence in favor of the idea that dyslexic readers would have noisier neural representations than typical readers.

Reevaluating the Neural Noise Hypothesis in Dyslexia: Insights from EEG and 7T MRS Biomarkers

“…Future research should include younger populations and incorporate a broader array of tasks, such as reading and phonological processing, to provide a more comprehensive evaluation of the E/I balance hypothesis. Additionally, our findings are consistent with another study by Tan et al (2022) which found no evidence for increased variability (’noise’) in behavioral and fMRI response patterns in dyslexia. Together, these results highlight the need to explore alternative neural mechanisms underlying dyslexia and suggest that cortical hyperexcitability may not be the primary cause of reading difficulties.…”

Verbal Working Memory‐Balance program training alters the left fusiform gyrus resting‐state functional connectivity: A randomized clinical trial study on children with dyslexia

“…Furthermore, a general hypothesis, the neural noise hypothesis, is recently raised in DD (Hancock et al, 2017). The neural noise hypothesis emphasizes sensory processing and representation deficits in DD, which precede and underlie phonological problems (Hancock et al, 2017; Tan et al, 2022; Ziegler et al, 2014). The neural noise hypothesis has also proposed that there are impairments in integrating visual symbols with their corresponding speech sounds (print–speech integration) (Hancock et al, 2017; Ziegler et al, 2020).…”

“…The anomalous temporal‐occipital cortex of individuals with dyslexia is conveyed in this hypothesis (Hancock et al, 2017). Although the neural noise hypothesis has the potential to explain the various facets of DD, it provides a basis for future works, and it needs more evidence to be supported (Tan et al, 2022).…”

Sensory temporal sampling in time: an integrated model of the TSF and neural noise hypothesis as an etiological pathway for dyslexia

“…However, there was an interaction between age and dyslexia for Cho in both visual and left temporoparietal cortex: dyslexic children had a lower absolute Cho concentration compared to control children, but this pattern did not hold among adults, who showed no effect of dyslexia status. Another paper from Tan et al ( 2022 ) attempted to quantify neural noise via a stimulus repetition paradigm, with the expectation that excessive noise would be reflected in more variable neural encoding of, and behavioral responses to, repeated stimuli. The researchers did not find any evidence to suggest that adults with dyslexia have noisier neural representations for spoken stimuli at the behavioral or neural level.…”