Theta-Band Modulation in EEG Signals from Individuals with Autism Spectrum Disorder Using Holo-Hilbert Spectral Analysis

Autism Spectrum Disorder (ASD) has been associated with neurofunctional alterations that affect communication, sensory integration, and performance in tasks requiring sustained attention. Among the most relevant electrophysiological markers in this context, the theta band (4--8 Hz) has received increasing attention due to its relationship with cognitive control, performance monitoring, and neural reorganization after mental effort. This study investigates theta-band modulation in electroencephalography (EEG) signals from individuals with ASD and neurotypical individuals, focusing on the parietal P3 and P4 channels before and after a sustained visual attentional task based on the Cancellation Test. The signals were acquired using the NeuroMap system (Neurotec, Brazil), with 21 channels arranged according to the international 10--20 system and a sampling frequency of 256 Hz. For spectral analysis, Holo-Hilbert Spectral Analysis (HHSA) was employed, as it can simultaneously represent carrier frequency and amplitude modulation in nonlinear and nonstationary signals. The results showed distinct patterns between groups: while the control group exhibited oscillatory reorganization compatible with functional adaptation after the task, the ASD group tended to show reduced reorganization and a statistically significant difference between pre-task and post-task states (p <0.05). These findings suggest that theta-band modulation may serve as a functional marker of attentional reorganization and demonstrate the potential of HHSA for characterizing subtle alterations in cortical dynamics in clinical populations.