The impact of heartbeat signals on auditory regularity processing in humans

The human brain forms expectations about incoming sensory stimuli based on past experiences. Research studies have primarily focused on investigating the neural mechanisms involved in processing sensory regularities based on the environmental (exteroceptive) signals. Recent studies have shown that the brain can also encode regularities established across exteroceptive and interoceptive (from inside the body) stimuli, such as the heartbeat signal.

In this study, we focus on cardio-audio regularities encoding, i.e. regularities induced by synchronizing the onset of administered sounds with the ongoing heartbeat. The goal is to investigate the spatio-temporal neural correlates of cardio-audio regularities encoding and how this process is influenced by attentional and consciousness levels. Two main experimental paradigms will be employed. The first paradigm focuses on regularities based on repeating identical sounds and unexpected sound omissions. The second experiment involves an associative learning paradigm, where regularity is based on repeatedly presenting a neutral stimulus followed by an alerting sound.

The initial part of the project involves an electroencephalographic investigation of the auditory omission response in healthy subjects. The subjects will actively monitor either the level of cardio- audio synchronization or auditory regularity to examine how internal and external attention affect the strength of the omission response. In a second project we will investigate in healthy subjects and comatose patients whether synchronizing sounds with the ongoing heartbeat improves the learning of temporal associations between sound pairs compared to fixed delays. Experiments on epileptic patients with intracranial electrodes will help to elucidate the spatio-temporal aspects of cardio-audio regularities based on Local Field potentials.

Through this project, the role of bodily signals in human auditory regularity processing will be systematically evaluated, shedding light on the conditions under which the brain utilizes their temporal characteristics to optimize sensory processing.