Nerve pathway · one in each half of the brain

Acoustic radiation

Also called Auditory radiation, Geniculotemporal radiation, Thalamocortical auditory fibers

The last stretch of the hearing pathway, from the thalamus to the hearing cortex.

The acoustic radiation lit up in a 3D model of the human brain

The acoustic radiation carries sound signals on the final leg of their journey. It runs from a relay station in the thalamus to the hearing cortex, tucked inside the big groove on the side of the brain. By the time sound gets here, it has already been cleaned up and analyzed in the brainstem. It delivers the signals to the cortex, where they become a voice, a song, or a car horn you consciously hear.

Where it is

Deep inside the side of the brain, starting near the optic radiation. It runs mostly sideways, from the thalamus out to Heschl's gyrus on the upper surface of the temporal lobe, hidden inside the big side groove.

What it does

Delivers sound

It carries signals from the medial geniculate nucleus in the thalamus to the primary hearing cortex.

Keeps pitch in order

Its fibers keep sounds sorted by pitch, so low and high notes land in different parts of the hearing cortex.

Think of it as the last short cable from the sound mixing board to the speakers in the concert hall.

Works with

Medial geniculate nucleusIt starts at this hearing relay station in the thalamus.
Primary auditory cortexIt ends at this primary hearing cortex, also known as Heschl's gyrus.
Inferior colliculusThis midbrain hub processes sound before passing it up to the thalamus and on to this radiation.
Vestibulocochlear nerve (VIII)The hearing journey begins in this nerve, which brings sound from the inner ear.
Superior temporal gyrusFrom the primary hearing cortex, sound spreads to this area to be recognized as speech, music, or noise.
Optic radiationIts visual cousin starts close by in the thalamus but heads to the back of the brain instead.

When it goes wrong

Damage on one side

Each ear sends signals to both sides of the brain, so damage on one side rarely causes deafness.

Damage on both sides

Rarely, damage on both sides can cause cortical deafness, even though the ears themselves work fine.

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

Surprising facts

By the time sound reaches this bundle, it has already passed through several relay stations in the brainstem, where the brain works out things like which direction it came from.

Where the name comes from

Acoustic comes from the Greek akouein, "to hear". Radiation describes how the fibers fan out toward the cortex.

Learn it in a lesson

Hearing and balanceFrom the inner ear to the cortex. 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 acoustic radiation?
Show the answer
Delivers sound. It carries signals from the medial geniculate nucleus in the thalamus to the primary hearing cortex.
The acoustic radiation 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 last short cable from the sound mixing board to the speakers in the concert hall."
Show the answer
Acoustic radiation. It is the acoustic radiation. The last stretch of the hearing pathway, from the thalamus to the hearing cortex.

Sources

Neuroscience Online, Chapter 13: Auditory System: Pathways and Reflexes, McGovern Medical School at UTHealth Houston
Primary auditory cortex, Radiopaedia
Internal capsule, Radiopaedia

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