Nerve pathway · one in each half of the brain

Arcuate fasciculus

Also called AF, Arcuate bundle

The curved cable linking the brain's areas for speaking and understanding words.

The arcuate fasciculus lit up in a 3D model of the human brain

The arcuate fasciculus is a curved bundle of fibers that links the speech-producing area at the front of the brain (Broca's area) with the language-understanding area further back (Wernicke's area). It arches around the deep groove on the side of the brain like a bow. It is thought to help you repeat what you hear, learn new words, and turn thoughts into the right speech sounds.

Where it is

Deep under the side of the brain, above your ear. It curves around the back end of the big side groove (the Sylvian fissure), running from the temporal lobe up, around, and forward into the frontal lobe.

What it does

Repeating words

It is thought to carry the sounds of words you hear to the areas that plan speech, so you can repeat a word or phrase.

Learning new words

Linking sound to speech is thought to help you pick up new vocabulary, including words in a foreign language.

Checking your speech

It is thought to help compare what you meant to say with what you actually said, so you can catch slips of the tongue.

Think of it as the phone line between a listener and a speaker: it lets the part that hears words pass them straight to the part that says them.

Works with

Broca's areaIts front end reaches this speech-planning area in the frontal lobe.
Superior temporal gyrusIts back end starts near Wernicke's area here, where the sounds of words are understood.
Middle temporal gyrusSome of its fibers reach this area, which helps link words to their meanings.
Supramarginal gyrusThis area near the bend of the arch is thought to help hold word sounds in mind for a moment, like a phone number you are about to dial.
Primary motor cortexIts front fibers also reach near the mouth and tongue area of the motor strip, which actually says the words.

When it goes wrong

Conduction aphasia

Damage in and around this bundle, often from a stroke, can cause conduction aphasia. People understand well and speak fairly fluently, but they struggle to repeat what they hear and mix up word sounds, like saying "pish" for "fish".

A bigger picture

Modern brain scans show the story is more than one cable. Damage to the nearby cortex can cause similar problems, and this bundle works within a wider language network.

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

Surprising facts

Carl Wernicke predicted in the 1870s that cutting the link between two language areas should cause its own kind of language problem, now called conduction aphasia.

Where the name comes from

From the Latin arcuatus, "bent like a bow", and fasciculus, "little bundle". The curved little bundle.

Learn it in a lesson

LanguageHearing, understanding, speaking, reading. A short guided lesson in 3D.

Quick quiz

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

Which of these is a job of the arcuate fasciculus?
Show the answer
Repeating words. It is thought to carry the sounds of words you hear to the areas that plan speech, so you can repeat a word or phrase.
The arcuate fasciculus is part of which larger structure?
Show the answer
White matter pathways. It belongs to the white matter pathways.
Which part fits this description? "Like the phone line between a listener and a speaker: it lets the part that hears words pass them straight to the part that says them."
Show the answer
Arcuate fasciculus. It is the arcuate fasciculus. The curved cable linking the brain's areas for speaking and understanding words.

Sources

Arcuate fasciculus, Radiopaedia
Neuroscience Online, Chapter 8: Higher Cortical Functions: Language, McGovern Medical School at UTHealth Houston

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