Cardiac signals modulate visual awareness

Abstract

We can investigate neural correlates of consciousness by measuring the brain response to different perceptual outcomes of the same stimulus (e.g., sensory threshold stimuli perceived in 50% of trials). Differences in perceptual awareness can arise from i) evoked brain responses for different perceptual outcomes and ii) from the pre-stimulus differences in brain activity. Cyclic variations of bodily signals can also influence perceptual awareness: baroreceptor activity during the systolic phase interferes with sensory stimulus processing, and the pre-stimulus response of the brain to the heartbeat (HEP) differs for stimuli subsequently seen or not. We presented subjects with near-threshold stimuli (Gabors overlaid with random-dot-noise) and compared i) the event-related potentials (ERPs) and ii) the HEP for the same stimuli when consciously seen and not. ERPs for seen and unseen differed as a function of cardiac phase: early sensory potentials (P1) were modulated during systole, while later cognitive potentials (VAN) were modulated during diastole. The HEP amplitude, topographic, and source space differences indicated that the default-mode-network is recruited for subsequently unseen stimuli and that the saliency-network is recruited for subsequently seen stimuli. Taken together, we show that the cardiac phase and the brain response to the heartbeat can influence conscious awareness at the visual threshold.