Contribution of Heart-Brain Interactions to Conscious Visual Perception
by Aishwarya Bhonsle
Date of Examination:2025-02-12
Date of issue:2025-06-27
Advisor:Prof. Dr. Melanie Wilke
Referee:Prof. Dr. Melanie Wilke
Referee:PD Dr. Roberto Goya-Maldonado
Persistent Address:
http://dx.doi.org/10.53846/goediss-11358
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Abstract
English
The objective of this thesis is to investigate the interplay between afferent cardiac signals and neural processing of exteroceptive inputs and how this dynamic contributes to conscious visual perception. This investigation is grounded in two EEG-ECG studies that explore how exercise-induced modulation of cardiac activity influences perceptual suppression, a phenomenon where a salient visual stimulus becomes subjectively invisible despite unchanged sensory input. Chapter 1 introduces the anatomical, physiological, and theoretical foundations of heart-brain interactions in conscious perception, framing the aims of the experimental studies. Chapter 2 presents the first experimental study, which investigates how light-intensity cycling exercise affects perceptual suppression, pre-stimulus alpha activity, and heartbeat-evoked potentials (HEPs) using the Generalized Flash Suppression (GFS) paradigm. Exercise reduced the likelihood of perceptual suppression and decreased alpha amplitudes, indicating increased cortical excitability. These results challenge the baroreceptor hypothesis, which predicts that increased heart rate should reduce cortical excitability and suppress sensory processing. Additionally, exercise-induced decreases in HEP amplitudes provide novel evidence of the influence of cardiac physiology on the neural processing of cardiac signals. However, HEPs did not predict perceptual suppression. Nonetheless, the concurrent observation of low alpha activity, reflecting increased cortical excitability, and low HEP amplitudes, suggesting decreased interoceptive processing, indirectly hints at a potential attentional trade-off between exteroceptive and interoceptive processing during exercise. Chapter 3 reports the second experimental study, which examines the impact of exercise-induced heart rate changes on perceptual suppression dynamics in the Motion-Induced Blindness (MIB) paradigm. Unlike the GFS findings, no significant effect of exercise was observed on perceptual suppression rate or duration, and no correlations were found between heart rate changes and suppression metrics. Stimulus-locked analyses of HEPs in a Replay condition revealed significantly lower amplitudes during physical target removal compared to target presence. However, response-locked analyses of HEPs in both MIB and Replay conditions showed no significant differences, indicating no difference in interoceptive processing concurrent with subjective perceptual changes. Taken together, these findings suggest that cardiac influences on perceptual suppression may depend on the cognitive and neural demands of the specific paradigm. While subtle indications of attentional trade-offs between interoceptive and exteroceptive processing were observed, these effects appear to operate independently of cortical excitability. The absence of a clear link between interoceptive signals and perceptual outcomes points to a modulatory, rather than deterministic, role for interoception. Furthermore, the results reinforce the idea that neural variability plays a more prominent role in shaping perceptual processes than cardiac influences. Chapter 4 discusses the broader implications of these findings on the role of heart-brain interactions in conscious perception, highlights the limitations of the present studies, and outlines potential directions for future research.
Keywords: heart-brain; interoception; heartbeat-evoked potentials; EEG; ECG; visual perception; consciousness
