Demographic and Behavioral Characteristics of the Entire Sample of 120 Participants.

Selected results for the EEG E/I balance biomarkers.

(A) Power spectral densities averaged across 3 electrodes (T7, TP7, TP9) corresponding to the left superior temporal sulcus (STS) separately for dyslexic (DYS) and control (CON) groups at rest and (C) during the language task. (B) Plots illustrating results for the exponent, offset, and the beta power from the left STS electrodes at rest and (D) during the language task.

Selected results for the MRS E/I balance biomarkers.

(A) Sample MRS voxel localization. (B) Sample MRS spectrum with individual total creatine (tCr), Glu and GABA+ contributions plotted below. (C) Group results (CON > DYS) from the fMRI localizer task for words compared to the control stimuli (p < .05 FWE cluster threshold) and overlap of the MRS voxel placement across participants. (D) MRS spectra separately for the dyslexic (DYS) and control (CON) groups. (E) Plots illustrating results for the Glu, GABA+, Glu/GABA+ ratio and the Glu/GABA+ imbalance.

Semi-partial Correlations Between MRS and EEG Biomarkers of Excitatory-Inhibitory Balance.

For Glu the Effects of Age and Gray Matter Volume (GMV) Were Regressed, for GABA+, Glu/GABA+ Ratio and Glu/GABA+ Imbalance the Effect of GMV was Regressed, While for Exponents and Offsets the Effect of Age was Regressed

Relationships between EEG and MRS E/I balance biomarkers.

(A) Semi-partial correlation between offset at rest in the left superior temporal sulcus (STS) electrodes and Glu controlling for age and gray matter volume (GMV). (B) Semi-partial correlation between exponent at rest in the left STS electrodes (controlled for age) and Glu/GABA+ imbalance (controlled for GMV).

Semi-partial Correlations Between Reading, Phonological Awareness, Rapid Automatized Naming, Multisensory Integration and Biomarkers of Excitatory-Inhibitory Balance.

For Reading, Phonological Awareness and Multisensory Integration the Effect of Age was Regressed, for Glu the Effects of Age and Gray Matter Volume (GMV) Were Regressed, for GABA+, Glu/GABA+ Ratio and Glu/GABA+ Imbalance the Effect of GMV was Regressed, While for Exponents and Offsets the Effect of Age was Regressed

Associations between beta power, phonological awareness and reading.

(A) Semi-partial correlation between phonological awareness controlling for age and beta power (in the left STS electrodes) at rest and (B) during the language task. (C) Partial correlation between phonological awareness and reading controlling for age. (D) Mediation analysis results. Unstandardized b regression coefficients are presented. Age was included in the analysis as a covariate. 95% CI – 95% confidence intervals; left STS – values averaged across 3 electrodes corresponding to the left superior temporal sulcus (T7, TP7, TP9).