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# Auditory cortex

The auditory cortex is a small area hidden on the top of the [temporal lobe](https://durgical.com/en/anatomy/middle-temporal-gyrus/); it is the first part of the brain's surface to process sound.

Official name: Transverse temporal gyri

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## What it is

Small gyri hidden on the top of the temporal lobe.

## What it does

First cortical stop for sound.

## Key points

- Each ear projects to both hemispheres, so a one-sided cortical lesion does not cause deafness in one ear; at most it blurs sound localisation on the opposite side
- Tonotopic map: low frequencies at the lateral end of Heschl gyrus, high frequencies at the medial end
- Bilateral damage causes cortical deafness or auditory agnosia (sounds are heard but not recognised); pure word deafness spares non-speech sounds

## Key facts

**Where**
Transverse temporal gyri (Heschl) in the lateral sulcus

**Blood supply**
MCA

**Function**
Primary auditory cortex (areas 41, 42)

## Relations

**Course**
Cochlear nerve, cochlear nuclei, superior olivary complex, lateral lemniscus, inferior colliculus and medial geniculate body, then the auditory radiation through the sublenticular part of the internal capsule

**Above**
Frontoparietal operculum, which covers it inside the [lateral sulcus](https://durgical.com/en/anatomy/lateral-sulcus/)

**Medial**
Posterior [insula](https://durgical.com/en/anatomy/insula/), toward which the transverse gyri run obliquely

**Behind**
Planum temporale, with [Wernicke's area](https://durgical.com/en/anatomy/superior-temporal-gyrus/) on the dominant side

**Below**
The rest of the superior temporal gyrus on the lateral surface

## How to find it

It lies on the upper surface of the temporal lobe inside the lateral sulcus, so it is seen only when the fissure is opened. The transverse temporal gyri (Heschl) run obliquely from the lateral surface toward the insula; on axial and sagittal MRI they form a mushroom or omega shape in the superior temporal plane.

## On imaging

Axial and sagittal MRI show Heschl gyrus as an oblique fold on the upper surface of the temporal lobe, sometimes doubled. Infarcts or bleeds here appear on DWI or CT in the [middle cerebral artery](https://durgical.com/en/anatomy/middle-cerebral-artery/) territory. Because each ear reaches both sides, a one-sided lesion rarely explains deafness in one ear: that calls for audiometry and MRI of the [internal acoustic meatus](https://durgical.com/en/anatomy/internal-acoustic-meatus/) instead.

## Clinical notes

- Seizures starting here produce simple sounds, such as buzzing or ringing, rather than voices or music
- Because hearing is represented on both sides, a one-sided temporal stroke or operation rarely changes pure-tone audiometry

## Anatomical variants

- One transverse gyrus or a duplicated one; duplication is common, more often on the right (some texts)

## Memory aid

Auditory pathway, "E. COLI M": Eighth nerve, Cochlear nuclei, superior Olive, Lateral lemniscus, Inferior colliculus, Medial geniculate body.

## Related conditions

- [Presbycusis (age-related hearing loss)](https://durgical.com/en/conditions/presbycusis/)

## Test yourself

Think of the answer, then tap the question to see it.

## Where is the primary auditory cortex?

On the transverse temporal gyri (Heschl), on the upper surface of the temporal lobe hidden inside the lateral sulcus (areas 41 and 42).

## Why does a one-sided lesion of the auditory cortex not cause deafness in one ear?

Each ear projects to both hemispheres; at most a one-sided lesion blurs sound localisation on the opposite side.

## What does bilateral damage to the auditory cortex cause?

Cortical deafness or auditory agnosia (sounds heard but not recognised); pure word deafness spares non-speech sounds.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
gyri temporales transversi TA2 5491

**Official Spanish (DeCS)**
Corteza Auditiva DeCS D001303

**English (TA2)**
Transverse temporal gyri

**Also called**
Heschl's gyri · heschl’s transverse convolutions

Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=1308); [Neuroanatomy, Cerebral Cortex](https://www.ncbi.nlm.nih.gov/books/NBK537247/); [Neuroanatomy, Sylvian Fissure](https://www.ncbi.nlm.nih.gov/books/NBK574552/); [Neuroanatomy, Temporal Lobe](https://www.ncbi.nlm.nih.gov/books/NBK519512/).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/transverse-temporal-gyri/