Integrating Cardiac Cycle Phases into Event Related Potential Analysis: A Protocol for Two-Dimensional and Virtual Reality Environments.

The heartbeat is a fundamental physiological rhythm that not only sustains life but also modulates perceptual and neural processes, thereby influencing the reproducibility of event-related potentials (ERPs). While virtual reality (VR) offers highly immersive environments compared to conventional two-dimensional (2D) screens, it also introduces unique challenges for electrophysiological recording, including motion artifacts, presentation latency, and potentially stronger cardiogenic modulation. These factors can diminish the efficiency of standard electroencephalography (EEG) preprocessing, leading to substantial data loss. This study presents a detailed protocol that combines simultaneous EEG and electrocardiography (ECG) to investigate heart-brain interactions under both VR and 2D conditions. The approach involves precise alignment of stimuli with cardiac signals, correction for VR-induced latency, and extended artifact management. Segmentation of EEG epochs based on whether stimuli occurred during cardiac systole or diastole revealed a robust suppression of visual ERP amplitude during systole. Critically, this suppressive effect was nearly identical in both VR and 2D environments, demonstrating the protocol's efficacy and confirming that this fundamental heart-brain interaction is resilient to changes in immersion level. This protocol, thus, offers a standardized framework for investigating cardiac influence on cognition, adaptable to diverse visual presentation methods.