Posterior commissure at a glance
- What it is
- The posterior commissure is a small bundle of fibres crossing the midline at the junction of the midbrain and third ventricle.
- Location
- It lies at the dorsal end of the cerebral aqueduct, just below the pineal gland.
- Function
- It connects pretectal nuclei and takes part in the consensual pupillary light reflex and vertical gaze coordination.
- Body system
- Nervous · single, midline structure
- FMA ID
- FMA62072 (Foundational Model of Anatomy)
Key facts
- Related to the pineal recess of the third ventricle.
- Fibres crossing in it link the pretectal nuclei of both sides, which is why light in one eye constricts both pupils.
Clinical relevance
Compression, for example by pineal tumours, can cause Parinaud syndrome (impaired upward gaze).
Structures next to the posterior commissure
The nearest named structures in the 3D model, measured from the centre of each part:
- Hair of head · skin
- Superior colliculus · nervous
- Cerebral aqueduct · nervous
- Choroid plexus of cerebral hemisphere · nervous
- Pineal body · endocrine
- Brachium of inferior colliculus · nervous
- Midbrain · nervous
- Commissure of fornix of forebrain · nervous
- Third ventricle · nervous
- Inferior colliculus · nervous
References
- Foundational Model of Anatomy: Posterior commissure (FMA62072). EMBL-EBI Ontology Lookup Service.
- OpenStax. Anatomy and Physiology 2e, §12.1 Basic Structure and Function of the Nervous System. Rice University, 2022.
- Mitsuhashi N. et al. (2009). BodyParts3D: 3D structure database for anatomical concepts. Nucleic Acids Research 37, D782–D785. Data © The Database Center for Life Science, CC BY 4.0.
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