Conscious processing of narrative stimuli synchronizes heart rate between individuals

Abstract

Heart rate has natural fluctuations that are typically ascribed to autonomic function. Recent evidence suggests that conscious processing can affect the timing of the heartbeat. We hypothesized that heart rate is modulated by conscious processing and therefore dependent on attentional focus. To test this we leverage the observation that neural processes can be synchronized between subjects by presenting an identical narrative stimulus. As predicted, we find significant inter-subject correlation of the heartbeat (ISC-HR) when subjects are presented with an auditory or audiovisual narrative. Consistent with the conscious processing hypothesis, we find that ISC-HR is reduced when subjects are distracted from the narrative, and that higher heart rate synchronization predicts better recall of the narrative. Finally, patients with disorders of consciousness who are listening to a story have lower ISC, as compared to healthy individuals, and that individual ISC-HR might predict a patients’ prognosis. We conclude that heart rate fluctuations are partially driven by conscious processing, depend on attentional state, and may represent a simple metric to assess conscious state in unresponsive patients.

Cognitive processing of a common stimulus synchronizes brains, hearts, and eyes

“…The strength of ISC observed here as well as the modulation with attention and correlation with memory performances are in line with previous reports for heart rate 10 , gaze position, pupil size 3 and EEG 17,19,34 . The novel finding is that ISC is co-modulated in these signals across subjects and across time.…”

“…However, this alternative interpretation does not explain the co-modulation of ISC observed across subjects. It also does not readily explain the co-modulation in heart and eyes, nor the observation that ISC of the heart is predictive of memory, a phenomenon that persists for audio-only narratives 40 . In contrast, the effects of attention and on memory observed here are straightforward consequences of the cognitive processing hypothesis, which in our definition includes perceptual processing of the stimulus.…”

“…The interpretation that cognitive processing is required for ISC to emerge is consistent with the observation that it is modulated by attention for many of these modalities. Specifically, when subjects are distracted from the stimulus, ISC drops significantly for gaze position, pupil size, EEG as well as heart rate 3,10,19 . To compare these effects across modalities and determine their time scales, we performed a new experiment in which N=29 subjects watched videos while normally attending, and then again while distracted by a mental arithmetic task.…”

“…Synchronization of physiological signals between individuals has often been attributed to physical or social interaction [4][5][6][7] . However, the simultaneous experience is not a prerequisite for physiological synchronization, as a number of studies have shown that physiological signals can be correlated between subjects even when they engage individually with dynamic natural stimuli 3,[8][9][10][11] .…”

Physiological Synchrony in EEG, Electrodermal Activity and Heart Rate Detects Attentionally Relevant Events in Time

“…Positive results found in these contexts may (partly) be driven by shared attentional engagement to external events, as connectedness between people may be strongly associated with mutual attentiveness ( Tickle-Degnen and Rosenthal, 1990 ). Recently, it was found that PS in EDA and heart rate can indeed reflect shared attention toward narrative stimuli ( Pérez et al, 2020 ; Stuldreher et al, 2020 ).…”