All parts of the brain › Functions › Itch

What part of the brain feels an itch?

No single itch centre. Itch starts in thin unmyelinated nerve fibres in the skin, is passed on by a dedicated set of cells in the spinal cord’s dorsal horn and climbs the spinothalamic tract to the thalamus, the same route as pain. In the cortex it lights the somatosensory cortex on the postcentral gyrus, the insula and the anterior cingulate cortex, with motor areas that prepare the scratch. [1][2][3][4]

The spinal cord (central canal), the thalamus, the postcentral gyrus, the insula and the cingulate gyrus lit in red on a 3D model of the brain, seen from the front left and above

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Lit: whole parts; region borders not drawn.

Slice

All 5 parts are lit together. Drag to turn, pinch or scroll to zoom, tap a part on the brain or a name in the list to focus it; .

The anterior cingulate cortex is a region on a lit gyrus, not a separate shape. The 3D model draws only whole gyri, so the gyrus that holds each area is lit; the area’s exact border is not drawn.

Itch: 5 parts lit

Spinal cord (central canal), thalamus, postcentral gyrus, insula and cingulate gyrus. Tap one to see where it is and what it does.

The parts and their roles

In lamina I of its dorsal horn, cells carrying the receptor for gastrin-releasing peptide pass itch on: mice without the receptor scratched far less at itchy substances yet reacted to pain normally, and lamina I spinothalamic cells fire to histamine just as people feel itch. [2][5] Where is the spinal cord?
Itch-excited spinothalamic fibres end in its posterior and ventral posterior regions, though little is known about which thalamic cells respond; one PET study of histamine itch saw no thalamic activity, while imagining itch did light it. [6][3][7] Where is the thalamus?
Holds the primary somatosensory cortex; histamine itch on the right forearm activated the somatosensory cortex mainly on the opposite side, more strongly as the histamine dose rose. [8][3] Where is the somatosensory cortex (postcentral gyrus)?
Its activity rose with the histamine dose, its back part tracked how unpleasant the itch felt, and its front part lit up when people only imagined itching. [3][7] Where is the insula?
Holds the anterior cingulate cortex (Brodmann area 24), active with the supplementary motor and premotor areas during histamine itch; the authors tied it to how the itch feels and the motor areas to preparing the scratch. [4][3] Where is the cingulate gyrus?

Named areas on the lit gyri

Anterior cingulate cortex, on the : On the cingulate gyrus; its Brodmann area 24 was active during histamine itch alongside the motor areas that prepare scratching. [4]

How they work together

Itch and pain share a road: their unmyelinated fibres both start in the skin and use the same nerve bundle and spinothalamic tract, but pain sets off a reflex to pull away and itch a scratch reflex. [1]
Separate lanes on the shared road: in primates, histamine and cowhage, a plant whose hairs itch without histamine, excite different groups of spinothalamic neurons that keep the two kinds of itch apart. [6]
Why scratching helps: in primates, spinothalamic neurons that fired to histamine fired less after the skin was scratched, an inhibition that seems to switch on only during itch. [6]
Itch reaches the motor system: histamine itch activated the supplementary motor area, premotor cortex and primary motor cortex on both sides, which the PET studies read as preparing to scratch. [3][4]
Honest limit: these are networks seen in imaging and animal work, not single centres; the itch scans mostly prick histamine into healthy skin in small groups (six men in one PET study), the areas they light overlap heavily with pain’s, the thalamus is lit because the spinal fibres end there although that study saw no thalamic activity, and the anterior cingulate cortex is a region on a lit gyrus, so whole parts are lit, not exact borders. [3][6][9]

Itch travels with pain and temperature rather than with fine touch: a cut through the lateral spinothalamic tract disrupts itch along with pain and temperature, and the touch page lights the postcentral gyrus, thalamus and the rest of the body-feeling network. [5] What part of the brain feels touch, temperature and pain?

Sources

Facts describe anatomy and normal function only. A part lit here takes part in feeling an itch; it does not do it alone, and it does other jobs too. The 3D model is the adult male BodyParts3D brain (credits and licence); on it the brainstem includes the midbrain, pons and medulla, so lighting the brainstem lights all three.