Abstract
Mounting evidence suggests that interoceptive signals are fundamentally important for the experience of the self. Thus far, studies on interoception have mainly focused on the ability to monitor the timing of ongoing heartbeats and on how these influence emotional and self-related processes. However, cardiac afferent signalling is not confined to heartbeat timing and several other cardiac parameters characterize cardiodynamic functioning. Building on the fact that each heart has its own self-specific cardio-dynamics, which cannot be expressed uniquely by heart rate, we devised a novel task to test whether people could recognize the sound of their own heart even when perceived offline and thus not in synchrony with ongoing heartbeats. In a forced-choice paradigm, participants discriminated between sounds of their own heartbeat (previously recorded with a Doppler device) versus another person’s heart. Participants identified the sound of their own heart above chance, whereas their metacognition of performance – as calculated by contrasting performance against ratings of confidence - was considerably poorer. These results suggest an implicit access to fine-grained neural representations of elementary cardio-dynamic parameters beyond heartbeat timing.
Highlights
Thanks to new experimental paradigms, recent studies indicate that interoceptive signals are constantly integrated with exteroceptive signals - even if often at an implicit level - in order to build a coherent representation of the own body[21,22]
To control for the possibility that own-heart recognition could be merely due to cardiac timings or to a general knowledge about their own heart rate, the samples of the other-heart sound were matched in heart-rate
Our findings extend recent empirical research which has indicated that participants integrate externally presented auditory or visual cues with cardiac signals during body-related processing[21,22,23]
Summary
In a similar line of research, a recent electrophysiological study has shown sensory suppression of heartbeat-related auditory tones - again without the participants’ explicit awareness[23] Both studies suggest that cardiac signals presented through an exteroceptive channel can activate and be compared with representations of interoceptive information (see [25]). It is worth noting here that in other domains, e.g. locomotion, it has been shown that people are able to monitor their movements online but can recognize their “motor signature” when asked to recognize their movement on a point light walker[29,30] as well as on a virtual character[31] from a third person perspective via offline visual presentation Such recognition seems to rely on an individual’s implicit knowledge about the intrinsic temporal dynamics of his/her movements, which has been gained, at least partially, through a lifetime of afferent proprioceptive and sensorimotor experiences[31]. A heartbeat counting task[13] was further used to enable us to relate the participant’s ability to recognise their own-heart sound recognition to a standard measure of interoceptive accuracy
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