EEG coherence studies in the normal brain and after early-onset cortical pathologies

Area of Science:

• Neuroscience
• Neurophysiology
• Developmental Neuroscience

Background:

• The corpus callosum (CC) facilitates interhemispheric communication, particularly for neurons processing similar visual orientations near the vertical meridian.
• Electroencephalography (EEG) coherence analysis provides a method to study CC functionality by measuring synchronized neural activity between hemispheres.

Purpose of the Study:

• To investigate the functional properties of the CC using EEG coherence analysis with visual stimuli.
• To examine the development and plasticity of CC connections in children with early visual pathway pathologies.

Main Methods:

• Presented iso-oriented and orthogonally-oriented gratings to different visual hemifields near or far from the vertical meridian.
• Measured interhemispheric coherence (ICoh) in the beta-gamma frequency band using occipital electrodes.
• Analyzed ICoh responses in control children and in patients with early visual lesions, congenital visual agnosia, or microgyria.

Main Results:

• Intact CC showed increased ICoh with iso-oriented gratings near the vertical meridian, localized to occipital electrodes in the beta-gamma band.
• Children with severe early bilateral visual lesions showed no ICoh response, unlike control children who developed this response.
• Patients with visual agnosia or microgyria exhibited altered or weaker ICoh responses, suggesting variations in cortical plasticity.

Conclusions:

• Visual stimulus-induced ICoh is a sensitive indicator of CC function and its development.
• Early visual pathway damage significantly impacts CC development and interhemispheric communication.
• The findings highlight the brain's plasticity and the diverse ways cortical connectivity adapts in response to early insults.