Increased top-down semantic processing in natural speech linked to better reading in dyslexia

Area of Science:

• Neuroscience
• Cognitive Science
• Developmental Psychology

Background:

• Developmental dyslexia is often linked to phonological processing deficits.
• Previous theories suggest individuals with dyslexia utilize contextual information for lexical access.
• Neuro-cognitive evidence for these compensatory mechanisms has been lacking.

Purpose of the Study:

• To investigate the neuro-cognitive underpinnings of contextual information use in developmental dyslexia.
• To examine online cortical tracking of auditory and semantic information in dyslexic and non-dyslexic readers.
• To correlate brain activity and structure with reading abilities.

Main Methods:

• Magnetoencephalography (MEG) was used to record brain activity in 41 adult Spanish speakers (14 with dyslexia).
• Multivariate Temporal Response Function analysis captured cortical tracking of speech envelope and semantic surprisal (derived from a Transformer Neural Network).
• Grey matter volume and reading scores were analyzed in relation to neural tracking.

Main Results:

• Right hemisphere speech envelope tracking correlated with phonological decoding in both groups, with dyslexic readers showing poorer performance.
• Increased grey matter volume in temporal and frontal areas was associated with better envelope tracking.
• Dyslexic readers showed a significant correlation between right hemisphere semantic surprisal tracking and word reading ability.

Conclusions:

• Findings support a deficit in speech envelope tracking in dyslexia.
• Evidence suggests semantic processing, specifically semantic surprisal tracking, acts as a compensatory mechanism in dyslexic readers.
• This highlights the role of top-down semantic strategies in overcoming reading challenges.