MODIFICATION OF CARDIAC INTEROCEPTION AND STRESS RESPONSIVENESS BY STIMULATION OF THE INTEROCEPTIVE BRAIN NETWORK

Interoception, the ability to perceive and interpret internal bodily signals, plays a crucial role in emotion regulation, stress responses, and overall well-being. Despite increasing interest in interoceptive processes, significant gaps remain in understanding their neural mechanisms, plasticity, and modulation by external factors such as brain stimulation and stress.
This dissertation explores interoceptive plasticity by investigating how Theta Burst
Stimulation (TBS) and acute stress influence interoceptive accuracy (IAc) and interoceptive attention (IAt), two distinct dimensions of interoception. IAc refers to an individual’s objective ability to perceive bodily signals, whereas IAt is reflected in the amplitude of heartbeat-evoked potentials (HEPs), which represent the neural response to cardiac signals. Additionally, this work aimed to refine the current theoretical models of interoception by examining the cortical sources of HEPs and their temporal dynamics.
Three studies were conducted. (1) The first aimed to investigate the effects of different TBS protocols —facilitatory intermittent TBS (iTBS), inhibitory continuous TBS (cTBS), and control intermediate TBS (imTBS)—on IAc and HEPs amplitude. (2) The second assessed how acute stress (SECPT) modulates interoceptive dimensions whether the same TBS protocols could have an impact on stress responsiveness. (3).The third mapped the cortical generators of HEPs using source estimation to examine the spatiotemporal dynamics of interoceptive processing under different conditions: spontaneous processing and attention-focused heartbeat
perception. Findings from the first study revealed that iTBS selectively enhanced IAt without affecting IAc, suggesting that interoceptive attention and accuracy rely on distinct neural mechanisms. The second study further supported this idea, showing that acute stress increased IAt (higher HEP amplitudes) but did not improve IAc. The unique whole-brain source analysis conducted in the last study revealed that interoceptive processing is distributed across multiple cortical regions, suggesting a progressive transformation of interoceptive signals, from early automatic processing to late-stage conscious and multisensory integration.
Taken together, these findings challenge existing deterministic vs. probabilistic models, proposing instead a hybrid model where interoceptive predictions unfold dynamically across time and cortical networks.
This dissertation provides novel insights into interoceptive plasticity, demonstrating
that interoceptive processes can be selectively modulated by neuromodulation and stress, emphasizing their dynamic and adaptable nature. By integrating neural, temporal, and cognitive perspectives, these findings contribute to the refinement of theoretical models of interoception and highlight the need for developing therapeutic interventions to address stress-related disorders.