Functional brain connectivity analysis in amyotrophic lateral sclerosis: an EEG source-space study

Amyotrophic Lateral Sclerosis (ALS) is a severe neurodegenerative disease, which affects domains outside of the motor system. Recent findings have suggested that scalp electroencephalography (EEG) analysis may represent a useful tool for the monitoring of the disease. Here, we investigated functional connectivity in a set of ALS patients using source-reconstructed EEG time series comparing the results to age-matched healthy controls. Source based functional connectivity was estimated using a measure of amplitude envelope correlation (AEC) after performing orthogonalisation procedure in the time domain. The results of this study show that alpha band functional connectivity at source level discloses different patterns of inter-regional synchronization in ALS patients compared to healthy subjects. These findings suggest that ALS induces a strong frequency-specific reduction of functional connectivity patterns and that these changes are not limited to motor connections.