Sensory processing and interoception

How the brain filters the outside world and reads the body from inside.

The worldThe filterFilterSkin

A schematic, not to scale — the places this mechanism works.

Part one — how this normally works

Filtering is the default job

Far more sensory information arrives than can be used. The nervous system predicts what should be there and mostly reports the difference, which is why a waistband disappears from awareness within seconds.

Interoception is the inside channel

Signals about heart rate, breath, gut, bladder, temperature and hunger are integrated in the insula into a felt sense of body state. That sense is what emotion is partly built from.

Proprioception needs good tissue feedback

Joint position sense depends on receptors in ligaments and capsules. Where end-range feedback arrives late, the brain gets a blurrier map and compensates with vision and effort.

Part two — what varies between bodies

Filtering thresholds vary by orders of magnitude between people, and that variation is developmental rather than acquired.
Interoceptive accuracy varies too: some people read body signals early and intensely, others notice only at extremes.
Both directions have costs — hypervigilance is exhausting, and low interoception delays recognizing a flare until it is large.

Part three — where it diverges

This is the first place conditions get named

Persistent differences in sensory filtering, interoception, attention regulation and social prediction are described as neurodivergence — most commonly autism and ADHD.
Blurry proprioception plus compliant tissue is a specific combination: the joint moves further and the brain notices later, which is why motor-control work matters more than stretching.
Under-registered interoception plus amplified pain processing makes pacing genuinely hard to learn without external data.
Sensory load and pain load add together, so a noisy clinic waiting room measurably raises pain before the appointment begins.

What moves this mechanism

Environmental control treated as a medical intervention, not a preference.
External data — heart rate, step counts, logs — where interoception is unreliable.
Proprioceptive drills, weight-bearing and slow controlled range over passive stretch.
Recovery built in before the crash rather than after.

Conditions that involve this mechanism

Where it is a primary mechanism

Where it contributes