ToesThe numbered map begins here, on the inner wall of the hemisphere. It runs up the wall, over the top and down the side, so the body lies upside down on the brain, with the toes at the upper end.
FootThe gyrus folds over the top edge of the hemisphere. It carries on down its inner face. That inner stretch, the paracentral lobule, serves the lower limb, and a side view of the brain cannot show it.
LegThe last part on the medial wall. Above it the gyrus curves out of the fissure, and the thigh and hip begin the stretch of the map that lies on the outer surface.
HipThe turning point of the map. Below it, on the inner wall, lie the leg, the foot and the toes; ahead of it, along the top of the hemisphere, comes the trunk.
TrunkA short strip for the largest part of the body. The share of cortex follows the density of touch receptors in the skin, not the area of skin, which is why the torso of the classic figure looks so small.
NeckFollows the trunk on the sensory map, as on the body. The motor map on the other half of the drawing puts its neck strip far from here, between the thumb and the brow.
HeadThe head has a short strip of its own beside the neck. The face is not part of it: the face is mapped much farther down the side, beyond the thumb.
ShoulderThe first of eleven strips for one upper limb. They are shoulder, arm, elbow, forearm, wrist, hand and five digits. The lower limb, toes to hip, has four.
Arm (upper arm)From shoulder to wrist the map keeps the order of the limb. The order is arm, elbow, forearm, wrist. That makes this stretch the easiest part of the strip to rebuild from memory.
ElbowIt is a short strip. The joints of the limb take little cortex compared with the hand they carry, because cortex follows the number of touch receptors in the skin and not the size of the part.
ForearmThe forearm continues the run down the limb. After the wrist the map slows down: the hand and each of its five digits get strips of their own.
WristThe last joint before the hand. From here to the thumb the map gives six strips to one hand, which is why the hand of the classic homunculus figure is drawn so large.
HandThe hand as a whole, before its five digits. After the lips it has the widest strip on the sensory map, because the skin here is densely supplied with touch receptors.
Little fingerThe five digits are mapped one by one. They run little finger first and thumb last as the strip goes down the side of the brain.
Ring fingerSecond in the run of digits. Every finger has a strip of its own on this map, while the whole upper arm, between the shoulder and the elbow, has just one.
Middle fingerThe center of the five digits on the hand and the map. In a real brain neighboring areas overlap, so the clean borders between the fingers are a convenience of the drawing.
Index fingerNext to the thumb on the map, as on the hand. The five digits keep their order, so the index finger lies between the middle finger above it and the thumb below.
ThumbThe thumb ends the run of digits. Straight after it the map jumps to the eye and the face, so the thumb and the face are neighbors on the cortex although they are far apart on the body.
EyeThe eye opens the face region. On the classic figure the face is drawn upright while the body above it hangs upside down. Versions that follow the 1950 figure label this strip eyelid and eyeball.
NoseThe order down the side is eye, nose, face, lips. That is roughly the order from the top of a face to the bottom, which is how the face areas of the map are arranged.
FaceThe face region follows the digits. It runs down toward the lateral sulcus. The hands, lips and face of the classic figure are drawn far too large for its body, because they are the most richly innervated.
LipsThe lips and the hands take the most cortex. It is shared out by the density of touch receptors in the skin, not by the size of the part. Fuller versions of the figure give the upper and the lower lip a strip each.
Teeth, gums and jawOne strip for three things: the teeth, the gums and the jaw. From here down, the map covers the inside of the mouth and the throat.
TongueLies near the bottom of the gyrus, close to the lateral sulcus. Like the lips it gets a large strip for a small part: speaking, like handling things and facial expression, matters a great deal to humans.
Pharynx (throat)The end of this drawing's sensory map, at the lateral sulcus. Fuller versions of the figure add one more area below it, for sensation from inside the abdomen.
Motor map: 22 parts 22
Toes (motor)The motor map also starts on the inner wall. There the leg area of the precentral gyrus folds into the longitudinal fissure. The sensory map lies just behind it, across the central sulcus.
Ankle (motor)A joint, where the sensory map names the foot. The motor strip is labeled by what moves, so the lower limb reads toes, ankle, knee, hip.
Knee (motor)The last motor strip on the medial wall. The sensory map has the leg at this place; the motor map names the joint that the muscles move.
Hip (motor)The corner strip of the motor map. It matches the hip on the sensory side. The large muscles around the hip share this one short strip. The hand, farther along, has six strips.
Trunk (motor)A short strip for a large mass of muscle. The little man of the classic motor figure has a thin torso under an outsized hand and face.
Shoulder (motor)On the motor map the shoulder follows the trunk directly. The sensory map puts the neck and the head between them; the motor neck comes much later, after the thumb.
Elbow (motor)The motor map names the upper limb by joints: shoulder, elbow, wrist. The sensory map adds the stretches of skin between them, the arm and the forearm.
Wrist (motor)The last joint before the hand. Shoulder, elbow and wrist have short strips; the hand that follows is, with the lips, the widest strip on the motor map.
Hand (motor)With the lips, the widest strip on the motor map. Skilled movements of the hand and fingers take far more cortex than the large muscles of the trunk and hip.
Little finger (motor)The digits run in the same order as on the sensory map. The little finger comes first. In a real motor cortex the finger areas overlap a great deal. The clean borders belong to the drawing.
Ring finger (motor)Second of the five digit strips. The sensory map gives the digits the same five strips in the same order, so the hand is the easiest stretch to carry from one map to the other.
Middle finger (motor)The center of the five digit strips. The ring finger is above it and the index finger below, as on the sensory side.
Index finger (motor)Next to the thumb, as on the hand. It is the fourth digit strip on the way down, and the thumb strip that follows is the widest of the five.
Thumb (motor)The thumb ends the digits on this map too. The strip that follows is a surprise: the motor neck, which the sensory map keeps up on top beside the trunk.
Neck (motor)Sits between the thumb and the brow on the motor map. It is at the start of the head region. On the sensory map it lies on top of the hemisphere, between the trunk and the head.
Brow (motor)The motor map names the parts of the head that move. The brow is the first of them, followed by the eyelid and eyeball, the face, the lips and the jaw.
Eyelid and eyeball (motor)Movements of the eyelid and of the eyeball share one strip. The sensory map has its eye strip in the matching stretch, straight after its thumb.
Face (motor)A wide strip between the eyelid and the lips. The motor face is the muscles of expression, so it lies with the other moving parts of the head: brow above, lips and jaw below.
Lips (motor)Wide on both maps. The orofacial, laryngeal and tongue areas fill the lower end of the precentral gyrus, the end nearest the lateral sulcus.
Jaw (motor)The motor map has a strip for the jaw alone. The sensory map groups the jaw with the teeth and gums, which can be felt but not moved.
Tongue (motor)Lies second from the bottom, between the jaw and swallowing. It is at the lower end of the precentral gyrus beside the lateral sulcus. The sensory tongue sits at the same level on the other half.
Swallowing (motor)The motor map ends with an action, not a part: swallowing. The sensory map ends at the same level with the pharynx (throat).
How this list was compiled: Every part name, the order of the parts and every detail line were checked again on 2026-09-30, for facts only and with nothing copied, against sources read that day. Penfield and Rasmussen, The Cerebral Cortex of Man, Macmillan, 1950, searched in the scan at https://archive.org/details/cerebralcortexma0000wild (the labels of its cross-section chart and of its sensory and motor homunculus figures: on the postcentral side toes, foot, leg, hip, trunk, neck, head, shoulder, arm, elbow, forearm, the five digits from little finger to thumb, eyes, nose, face, upper lip, lips, lower lip, teeth, gums and jaw, tongue, pharynx, intra-abdominal; on the precentral side toes, ankle, knee, hip, trunk, shoulder, elbow, wrist, hand, the five digits, neck, brow, eyelids and eyeballs, face, lips, jaw, tongue, with vocalization, salivation and mastication beside the lower strips). Two renderings of those figures on Wikimedia Commons, read for their labels and the order of the labels only: https://commons.wikimedia.org/wiki/File:Sensory_Homunculus-en.svg (CC BY 3.0, redrawn from a college textbook figure; the 25 sensory labels used here, with wrist and hand, plus genitals) and https://commons.wikimedia.org/wiki/File:Homunculus-ja.svg (public domain, a translation of https://commons.wikimedia.org/wiki/File:Homunculus-de.svg, whose description credits Penfield and Rasmussen 1950; both maps, with the position of every label, and swallowing as the last motor label). Wikipedia, text only: Cortical homunculus, https://en.wikipedia.org/wiki/Cortical_homunculus (Penfield with Boldrey and Rasmussen; homunculus, Latin for little man; the toes at the upper end, where the cortex curls inward; cortex allotted by how richly a region is innervated, so the hands, lips and face are large and the torso small; face areas in roughly top-to-bottom order; teeth, gums, jaw, tongue and pharynx, then an intra-abdominal area; the traditional and disputed place of the genitals beyond the toes; overlap between neighboring regions; calls since the 2010s to revise the classic model); Primary somatosensory cortex, https://en.wikipedia.org/wiki/Primary_somatosensory_cortex (postcentral gyrus of the parietal lobe; Brodmann areas 3, 1 and 2; cortex in proportion to the density of touch receptors, lips and hands largest; each hemisphere maps the opposite side of the body); Postcentral gyrus, https://en.wikipedia.org/wiki/Postcentral_gyrus (bounded by the longitudinal fissure, the central sulcus, the postcentral sulcus and the lateral sulcus); Paracentral lobule, https://en.wikipedia.org/wiki/Paracentral_lobule (on the medial surface, the continuation of the precentral and postcentral gyri; the opposite lower limb); Primary motor cortex, https://en.wikipedia.org/wiki/Primary_motor_cortex (precentral gyrus; the leg area folding into the longitudinal fissure; buttocks, torso, shoulder, elbow, wrist, fingers, thumb, eyelids, lips and jaw down the lateral surface; considerable overlap; not a map of single muscles); Motor cortex, https://en.wikipedia.org/wiki/Motor_cortex; Wilder Penfield, https://en.wikipedia.org/wiki/Wilder_Penfield. Catani, A little man of some importance, Brain 140(11), 2017, open access at https://europepmc.org/article/PMC/PMC5841206 (first published 1 December 1937 by Penfield and Boldrey in Brain; 126 patients operated under local anaesthesia between 1928 and 1936; a second version in the 1950 book; the face upright and the body inverted; Penfield's own warning about shape and comparative size). Licence: own work
The drawing: Drawn for this site on 2026-10-05 by script. Our own drawing, nothing traced. The strips come from our own part list and outline formula; renderings of the classic homunculus figures on Wikimedia Commons were read for the order of the parts only, no body sketches were taken over, and the numbers and labels are our own. The rest of the section (the folds of the cortex below the strips, the insula and temporal lobe, the corpus callosum, the ventricles, the thalamus, the caudate and lentiform nuclei, the internal capsule and the fibres that fan out of it, the hippocampus, the peduncles and the pons) is drawn freehand; what lies where follows two public domain plates in Henry Gray, Anatomy of the Human Body (20th US edition, 1918): fig. 717, coronal section of brain immediately in front of pons (https://commons.wikimedia.org/wiki/File:Gray717.png), and fig. 718, coronal section of brain through intermediate mass of third ventricle (https://commons.wikimedia.org/wiki/File:Gray718.png). A plan, not to scale: the section is widened to fit the strips, the widths of the strips are schematic, and the rim that carries the strips is drawn smooth, without its grooves. Licence: own work
How it works
This somatosensory cortex map cuts the postcentral gyrus from side to side and divides its cortex into strips, one for each body part, widest for the lips and the hand. The other half of the drawing is the motor map.
Read the full guide
The body lies upside down along the gyrus
Toes, foot and leg sit on the inner wall; the hip turns the corner. Trunk, neck, head and arm follow on top, then the hand and digits, little finger to thumb. The face runs down the side, eye to pharynx. Each hemisphere maps the opposite side of the body.
Why hands and lips get so much cortex
Cortex follows the density of touch receptors in the skin, not the size of the part. The lips and the hand get the widest strips and each finger one of its own; the whole trunk gets one short strip. The motor map is widest at the hand and lips too. Strip widths here are schematic: real areas overlap, and recent studies call for revising the classic map.
After the thumb comes the eye: the hand sits next to the face, the neck back by the trunk.
The motor strip differs: ankle and knee, the neck after the thumb, a brow, and swallowing at the end.
For a short round pick Sensory: arm and hand, 11 parts. Print blank puts both maps on one sheet.
Questions and answers
Who first mapped the somatosensory cortex?
The neurosurgeon Wilder Penfield. He touched the exposed cortex of patients under local anesthesia with a small electric current and noted each response. With Edwin Boldrey he published the first homunculus in the journal Brain in December 1937, from 126 patients.
Is this the same as the sensory homunculus?
Yes. Homunculus is Latin for little man, the distorted figure textbooks drape over this strip. It is left out here because the sketches give answers away. The 25 sensory parts are the usual textbook labels; the 22 motor parts follow Penfield and Rasmussen's 1950 figure.
What is left out of this map?
The genitals have no ring: they are traditionally drawn beyond the toes, but their place is not settled. Fuller versions add an intra-abdominal area below the pharynx. Brodmann areas 3, 1 and 2 run front to back, so this cut cannot show them.