Cortical area · one in each half of the brain

Supramarginal gyrus

Also called SMG, Brodmann area 40

Helps you sound out words, use tools, and tell your feelings from others'.

The supramarginal gyrus lit up in a 3D model of the human brain

A curved ridge in the lower parietal lobe that wraps around the back end of the big groove on the side of the brain. On the left side it helps with the sounds of language, like holding a phone number in mind by repeating it silently. It is also key for skilled actions such as using tools. On the right side it seems to help you notice when someone else feels differently than you do.

Where it is

In the lower part of the parietal lobe, just behind the touch strip. It curves like a horseshoe around the back tip of the lateral sulcus, the deep groove that separates the temporal lobe from the lobes above it.

What it does

Sounds of words

It helps break words into their sounds, which is vital for reading aloud and spelling.

Holding words in mind

It works like a short-term store for speech sounds, keeping a few words or numbers ready.

Using tools and gestures

On the left it helps with the "how to" of skilled actions, like using scissors or waving goodbye.

Seeing past your own feelings

On the right it seems to help you realize that other people may feel differently from you right now.

Think of it as a mental sticky note for sounds, where you keep a phone number alive by saying it over and over in your head.

Works with

Superior temporal gyrusIt works hand in hand with Wernicke's area just below it to process speech sounds.
Arcuate fasciculusThis curved cable of fibers links it and nearby language areas with speech areas at the front of the brain.
Broca's areaTogether they form a loop that silently rehearses words to keep them in mind.
Angular gyrus regionIts neighbor, the angular gyrus, helps turn the sounds it processes into meaning.
Primary motor cortexIt sends plans for skilled hand movements to the motor strip, which carries them out.

When it goes wrong

Conduction aphasia

Damage around this area and the fiber cable linked to it can make it very hard to repeat words or phrases, even though the person understands and talks fairly fluently.

Apraxia

After damage on the left, people may struggle to show how to use a toothbrush or comb, even though their muscles work fine and they know what the object is.

For learning only, not medical advice. If you have a health concern, talk to a doctor.

Surprising facts

When scientists briefly quieted the right supramarginal gyrus with magnetic pulses, people were more likely to judge others' feelings by their own.
Silently repeating a phone number to remember it uses a loop between this area and Broca's area.

Where the name comes from

From the Latin "supra" (above) and "margo" (edge). It curves above the edge of the lateral sulcus, the deep groove on the side of the brain.

Quick quiz

3 questions. Your answers are saved and come back in your daily review.

Which of these is a job of the supramarginal gyrus?
Show the answer
Sounds of words. It helps break words into their sounds, which is vital for reading aloud and spelling.
The supramarginal gyrus is part of which larger structure?
Show the answer
Parietal lobe. It belongs to the parietal lobe.
Which part fits this description? "Like a mental sticky note for sounds, where you keep a phone number alive by saying it over and over in your head."
Show the answer
Supramarginal gyrus. It is the supramarginal gyrus. Helps you sound out words, use tools, and tell your feelings from others'.

Sources

Supramarginal gyrus, Radiopaedia
Conduction Aphasia, StatPearls, NCBI Bookshelf
Apraxia, StatPearls, NCBI Bookshelf

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