This study examines the relationship between the autonomic nervous system and brain activity, focusing on the dynamic interaction between heart rate variability (HRV) and EEG signals. Artificial intelligence-based models have demonstrated that autonomic nervous system changes can predict future EEG patterns with 80% accuracy, while time-lag analysis shows that these changes precede brain activity modifications by 250–400 ms. The results confirm that the autonomic nervous system not only responds to brain functions but actively shapes them, offering a new perspective in neurophysiology, psychophysiology, and neurotechnology.