Individual Differences in Cortico-Cardiac Covariation and the Role of Threat Induction in an Auditory Oddball Paradigm
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Philipps-Universität Marburg
Abstract
Mind and body are deeply interconnected, particularly in the face of unpredictable threat,
where the brain’s threat detection system and physiological responses, such as heart rate
changes, adapt with threat imminence. However, it remains unclear how even benign events –
those without a signaling function or direct threat value – are processed within such contexts.
Investigating the temporal dynamics using reliable, replicable markers of adaptive threat
processing, including cortical components, cardiac responses, and their interaction, is crucial
for understanding how the brain and body coordinate under threat. Examining these markers
helps disentangle transient, context-driven responses from stable, trait-like threat sensitivity,
providing insight into the mechanisms that differentiate adaptive from maladaptive threat
responding.
This thesis investigates how contextual uncertainty and the processing of unexpected
but benign stimuli shape neural and cardiac responses. Using an auditory oddball paradigm
with a threat of shock manipulation in healthy individuals, we examined cortical processing
of expected vs. unexpected (i.e., deviant) stimuli in unpredictable threat vs. safe contexts via
event-related potentials (ERPs) and heart period (HP) responses. A crucial element was the
application of the cardio electroencephalographic covariance tracing (CECT) method, which
allowed within-subject analysis of brain-heart coupling with high temporal precision.
In Study I, unpredictable threat contexts heightened cortical responses, as evidenced
by enhanced early ERP components (N1 and P2), reflecting amplified sensory detection and
selective attention. P3 amplitude was elevated in response to unexpected stimuli, but this
effect was diminished in the threat condition. For HP, both the threat context and stimulus
expectedness independently contributed to stronger cardiac acceleration, suggesting additive effects of threat and stimulus expectedness on HP. Brain-heart coupling analyses revealed a
novel CECT component, P150H, linked to early cortical sensitivity (N1/P2) under threat, and
the posterior N300H, associated with later stages of stimulus discrimination (P3) and
subsequent cardiac acceleration.
Study II assessed the replicability, within-session reliability, and 6-month test-retest
reliability of Study I findings to identify markers for individual differences in response to
unpredictable threat. ERP responses (N1, P2, and P3) and HP measures demonstrated strong
test-retest reliability, with the N1 component emerging as a particularly reliable marker of
early sensory threat processing. While CECT components showed lower stability, they
remained replicable cortical correlates of HP change, providing valuable insights into brainheart
interactions, in which individuals reliably differ to some degree.
Taken together, this thesis demonstrates how cortical and cardiac systems interact to
cope with threats. It is argued that unpredictable threat not only modulates defensive
responses to direct threat cues but also shapes attention toward and evaluation of benign
stimuli unrelated to the threat. Initially, broad vigilance dominates, with later processing
stages distinguishing stimulus expectedness, suggesting that the neurobiological system
proactively adapts to uncertainty by monitoring both direct and indirect threat cues over time.
By assessing replicability and reliability through task-related difference scores, this thesis
ensures that observed effects reflect meaningful cortical and cardiac adaptations. Together,
these findings highlight the adaptive nature of threat responses in healthy individuals while
identifying potential pathways for maladaptive threat responding in anxiety-related disorders.