Investigating the Neuronal Correlates of “Normal” Hallucinations Using Event-Related Potentials (ERPs)

Abstract

Visual hallucinations (VH) are often associated with psychiatric, neurological, and ophthalmological conditions but can also occur in healthy individuals, known as “normal” hallucinations (NH). This study investigated the neuronal correlates of NH using event-related potentials (ERPs) recorded during a dual-task paradigm. Fourteen participants completed a task requiring simultaneous judgments of facial orientation and the visibility of a central square, with critical trials designed to induce NH by presenting no stimulus while eliciting perceptual ratings. Behavioral results replicated previous findings, with NH reported in 62.5% of critical trials. Higher visibility ratings in NH correlated with task accuracy and response clarity, suggesting NH involves genuine perceptual experiences influenced by cognitive mechanisms. However, ERP analysis revealed significant limitations in data quality due to the insufficient number of critical trials, leading to high noise levels and low signal-to-noise ratios (SNR), particularly in conditions with NH. While ERPs for the facial orientation task confirmed the recording setup’s reliability, no reliable ERPs were captured for NH due to insufficient statistical power. Future research should focus on optimizing experimental designs by increasing trial numbers, extending session durations, and refining preprocessing methodologies. It is advised to aim for at least 150 trials in future studies while maintaining a focus on improving electrode connectivity to enhance data quality and reliability.