Cardiac phase modulates behavior and response related lateralization in visual spatial conflicts during change detection.

The brain is in continuous bidirectional exchange with the heart, receiving and sending signals that not only sustain physiological regulation but also shape perceptual and higher-order cognitive processes. While attentional selection has long been conceptualized as a mechanism for guiding behavior through external sensory input, it remains unclear how afferent signals originating from the heart are integrated into this process. To investigate how such cardioafferent signals interact with attentional selection, we employed a change detection task synchronized to the cardiac cycle which induced perceptual conflicts by pairing task-relevant luminance changes with more salient orientation changes in the opposing hemifield. Seventy-six participants were pseudorandomized into two groups exposing them to either repeated cold pressor tests (CPT, N = 51) or a warm water control condition (N = 25) to probe cardiovascular drivers of cardiac cycle effects. Cardiac phase systematically modulated change detection: systolic onsets increased errors in spatial-conflict changes, biasing responses toward a salient distractor, and increased misses for isolated luminance changes. EEG lateralization in a central-posterior cluster implicated altered premotor response encoding rather than early sensory gating (change positivity, N1pc, N2pc) as the locus of these effects. Although exposure to the CPT elevated blood pressure and heart rate, we found no robust group-level modulation of the cardiac-phase effect; instead, individual differences in heart rate responses to the CPT as well as an interaction of systolic blood pressure and heart rate variability predicted the magnitude of spatial-conflict phase effects in the CPT group. Together, these results demonstrate that phasic bodily signals can bias visuomotor selection during perceptual conflicts and change detection.