Cardiac Signals Facilitate the Breakthrough to Awareness of Emotional Stimuli

The brain continuously integrates interoceptive signals-such as those arising from cardiac afferents-with sensory input to guide perception, emotion and awareness. Previous research has demonstrated that the timing of external stimuli relative to the cardiac cycle influences perceptual and cognitive processes. However, it remains unclear whether cardiac signals facilitate the access of emotional visual stimuli to conscious awareness. Here, we used a continuous flash suppression (CFS) paradigm to investigate whether the breakthrough of fearful and neutral faces to awareness is modulated by cardiac cycle phase. Fearful and neutral faces were presented to the non-dominant eye in synchrony with participants' heartbeats-either during estimated-cortical systole (ec-systole) or diastole (ec-diastole)-while dynamic Mondrian patterns suppressed visibility in the dominant eye. Results showed that fearful faces presented during estimated-cortical systole (ec-systole) broke through suppression faster and after fewer heartbeat-synchronized presentations than those presented during ec-diastole, suggesting facilitated processing. No significant cardiac modulation was found for neutral faces or in emotion discrimination accuracy, confidence, or response bias. These findings demonstrate that cardiac afferent signals selectively enhance the perceptual salience of motivationally salient (e.g., threat signaling) stimuli, promoting earlier access to consciousness. This study extends prior work by showing that cardiac influences on emotion processing operate even at early, preconscious stages of visual perception.