Aetiological factors in dyslexia: IV. Cerebral hemispheres are functionally equivalent

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Developmental Neuroscience

Background:

• Developmental dyslexia is a common neurodevelopmental disorder affecting reading acquisition.
• Previous research suggests potential differences in brain structure and function in dyslexic individuals.
• The parieto-occipital region is implicated in visual processing and reading, making it a key area of interest.

Purpose of the Study:

• To investigate differences in electroencephalography (EEG) spectral analysis and coherence between dyslexic and normal readers.
• To explore potential correlations between EEG findings and cerebral asymmetry in the parieto-occipital region.

Main Methods:

• Recording of electroencephalography (EEG) from left parieto-occipital leads in dyslexic and normal individuals.
• Analysis of frequency spectrum and EEG coherence values between and within hemispheres.
• Comparison with computed tomography (CT) scan data of parieto-occipital cerebral asymmetry.

Main Results:

• Dyslexic individuals exhibited a distinct frequency spectrum in parieto-occipital EEG compared to controls.
• Lower interhemispheric EEG coherence was observed in dyslexics, with greater intrahemispheric coherence.
• CT scans revealed reversed or absent cerebral asymmetry in the parieto-occipital regions of dyslexics.

Conclusions:

• The findings indicate significant differences in the functional organization of the left parieto-occipital areas in dyslexia.
• Altered patterns of interhemispheric and intrahemispheric connectivity are associated with dyslexia.
• The observed EEG and structural asymmetries suggest neurobiological underpinnings of reading difficulties in dyslexia.