Interventions and Manipulations of Interoception

Abstract

Interoceptive pathways may be manipulated at various levels to develop interventions to improve symptoms in a range of disorders. Primarily through the lens of the respiratory system, we outline various pathways that can be manipulated at neural, behavioral, and psychological levels to change the representation of and attention to interoceptive signals, which can alter interconnected physiological systems and improve functioning and adaptive behavior. Interventions can alter interoception via neuromodulation of the vagus nerve, slow breathing to change respiratory rate and depth, or awareness processes such as mindfulness-based interventions. Aspects of this framework may be applied to other physiological systems and future research may integrate interventions across multiple levels of manipulation or bodily systems.

Keywords: PTSD; interoceptive awareness; mindfulness; neuromodulation; respiration; substance use disorder.

Figure 1.. Interoceptive interventions of the Respiratory System.

Interventions of a given interoceptive system can be understood through four main domains: the intervention type, target(s), potential mechanisms, and clinical outcomes. The target(s) of an interoceptive intervention may include neural entry points that can impact upstream sensory or psychological functioning (e.g., the vagus nerve), or behavioral or psychological entry points which can impact downstream functioning (e.g., respiration rate and depth, interoceptive awareness and interpretation of respiratory sensations). The framework outlined here refers to the respiratory system and may be extended to aspects of other interoceptive systems. Mindfulness Approaches (top left). Mindfulness approaches may improve interoceptive awareness by cultivating attention to bodily sensations that is sustained and nonjudgmental. Mindfulness-ofbreath exercises engage neural networks involved in interoception (aIns, pIns), executive function, and emotion regulation (mPFC/ACC). Slow Breathing (bottom left). Slow breathing (or decreasing respiratory rate to ~5 breaths/min) is thought to activate cardiopulmonary baroreceptors, leading to reflex reductions in sympathetic nerve activity, resulting in lowered blood pressure. Vagus Nerve Stimulation (VNS) (top right). VNS is a form of neuromodulation where electrical stimulation is applied to the main trunk or peripheral receptors of the vagus nerve (such as through non-invasive auricular stimulation, targeting the auricular branch of the vagus nerve). Interoceptive afference can impact clinical outcomes via multiple physiological mechanisms, some of which are already well understood. For instance, afference that reaches conscious perception may also be linked with known baroreflex mechanisms which regulate heart rate. Additionally, parasympathetic vago-vagal reflexes that regulate stomach function involve signaling from the stomach that can reach interoceptive awareness. Such pathways may also be regulated by external input to the constitutive brainstem nuclei via interventions such as transcutaneous auricular vagus nerve stimulation, leading to plasticity in neural circuits both in the brainstem and higher brain centers. Note: the brainstem breathing central pattern generator is a complex network of interacting sites, here represented by its essential engine, the preBötzinger Complex. See [8] for more details. Clinical outcomes (bottom right) largely overlap among the three interventions due to targeting the respiration system at different levels of processing, and include ameliorated symptoms in cardiovascular functioning, pain, and psychiatric disorders. Further, interventions can have similar effects because they are inter-related; for example, mindful interoceptive awareness of breath sensations can result in slow breathing. This framework also highlights that interventions may be integrated and optimized by targeting multiple points in interoceptive pathways (such as VNS coupled with Mindfulness approaches). The “Clinical Outcomes” inset indicates which interventions are associated with which outcomes: V, Vagus Nerve Stimulation; S, Slow Breathing; M, Mindfulness approaches. Abbreviations: 5-HT, Serotonin; ACh, Acetylcholine; aIns, Anterior insula; Hyp, Hypothalamus; LC, Locus Coeruleus; mPFC/ACC, Medial prefrontal cortex / Anterior cingulate cortex; pIns, Posterior insula; NA, Noradrenaline; Namb/rVLM, Nucleus ambiguous / Rostral ventrolateral medulla; NTS, Nucleus Tractus Solitarii; PTSD, Post Traumatic Stress Disorder; Thal, Thalamus.