Respiratory interoception

The breath has been load-bearing on this wiki since the first ingest without ever being the subject of a page. It is the attentional anchor of mindfulness-meditation, the provocation in interoceptive-exposure, the channel Farb et al. name when they say training is domain-specific rather than general, and the system Weng et al. (2021) use as their case study for intervening on interoception at all.

This page exists mainly to record why that choice of case study is not neutral.

The exceptionality claim

Respiration is unique compared with other systems (e.g., gastrointestinal) insofar as conscious regulation can immediately impact respiratory processes and… respiratory processes can affect emotion and cognition. — Weng et al. (2021)

Two properties, and it is having both that makes breathing exceptional:

1. It is voluntarily drivable, immediately. You cannot decide to change your gastric motility, your bladder filling, your immune signalling or (much) your heart rate. You can change your breathing in one cycle. Interoception in every other channel is something the brain reads; here it is something the person can also write.
2. Driving it changes state. The change propagates — to sympathetic outflow via cardiopulmonary stretch receptors and the baroreflex (slow-breathing), and to cognition and emotion via the respiratory entrainment described below.

The methodological consequence is the one the wiki should carry: most of the field’s intervention evidence is respiratory evidence, and respiration is the channel least like the others. A framework validated on breathing generalizes to the gut and bladder only if the voluntary-control property was doing no work — and in the behavioural arm (slow-breathing) that property is the entire mechanism. Weng et al. concede the point obliquely, noting that “not all systems can be as readily consciously manipulated as the respiration system” and falling back, for those systems, on recognizing sensations rather than driving them.

The rhythm entrains the brain

Breathing is not only a signal to be sensed; its rhythm organizes activity elsewhere. The rhythm generator is the preBötzinger complex, a compact bilateral medullary nucleus that drives the inspiratory muscles and coordinates expiratory movement. Beyond driving muscle, breathing-related activity initiated there reaches suprapontine structures — hippocampus, prefrontal cortex, amygdala — and influences cognitive and emotional function (Tort et al. 2018; Zelano et al. 2016, on nasal respiration entraining limbic oscillations).

The same phasing shows up one synapse into the interoceptive pathway, and is exploitable: NTS relay neurons receive pulmonary-stretch and baroreceptor afference primarily during inhalation, and are proposed to receive facilitatory input during exhalation — which is why RAVANS gates stimulation to the exhalation window (see bioelectronic-medicine).

So the respiratory cycle is a timing structure for interoception generally, not merely one more channel. That is a further reason it is a bad representative case and a good intervention target.

Where the wiki already had this material

• Panic. Respiratory challenge elicits sensations that trigger panic (Nardi et al. 2009), and hyperventilation provocation is the paradigm case of interoceptive-exposure. The cognitive-model-of-panic and anxiety-sensitivity pages are largely about misread respiratory and cardiac sensation.
• Contemplative training. Breath sensitivity is the one interoceptive measure that contemplative training does seem to improve (Daubenmier et al. 2013), against a null for domain-general heartbeat accuracy — see does-mindfulness-enhance-interoceptive-accuracy. Long-term mindfulness training is associated with reliably lower resting respiration rate (Wielgosz et al. 2016), and meditation lowers respiratory rate even when breathing changes are not instructed.
• Primary interoceptive cortex. The posterior insula is “sensitive to the respiratory rate and putatively considered primary interoceptive cortex,” and mindfulness training raised its activation during a breath-focused task (Farb et al. 2013). See insular-cortex.
• Threat anticipation. Respiratory resistance can be parametrically manipulated with a device, and the anticipation versus the experience of respiratory threat are represented in ventrolateral versus lateral periaqueductal gray respectively (Faull et al. 2015) — one of the few places the wiki has an anticipation/experience dissociation with an anatomical address. Relevant to forecasting.

A measurement note

The wiki’s persistent complaint that interoception is measured almost entirely through the heart (see is-the-heartbeat-counting-task-valid) has a respiratory answer available and under-used. Breathing is measurable objectively and continuously without asking the participant anything, and it can be manipulated experimentally in a graded way. That it remains a secondary measure in a field bottlenecked on cardiac tasks is worth noting. The respiratory tasks named above — parametric resistance loading, breath-focus decoding, resting respiration rate — are alternatives already in use, none of them yet represented in this wiki by a primary source.