periaqueductal gray

periaqueductal gray (PAG)

The term periaqueductal gray (PAG) refers to the densely cellular core-structure surrounding the dorsal and lateral aspects of the cerebral aqueduct (AQU) in the midbrain (MBR). Defined histologically, it is the part of the central gray (CGR) that extends from the epithalamus and posterior hypothalamic area rostrally to the pontine central gray caudally ( Swanson-2004 ). Relative to surrounding structures, it extends approximately from the posterior commissure rostrally to the locus ceruleus caudally. It is bounded dorsally by the commissure of the inferior colliculus and commissure of the superior colliculi; and is bounded laterally by the tectospinal tract and the mesencephalic tract of the trigeminal nerve ( Carrive-2012 ). The PAG is distinguished from cellular structures ventral to the AQU by its homogeneity. It is found in the human ( Carpenter-1983 ), macaque ( Martin-2000 ), rat ( Paxinos-2009b ) and the mouse ( Franklin-2008 ). Indistinct boundaries within PAG have been identified on the basis of the shapes and sizes of cells. That has resulted in several different segmentations within and across species. The simplest segmentation reported to show a similar pattern across species is based on multiple criteria ( Carrive-2012 ). By that criterion, areas stained with greater or lesser intensity are grouped into four longitudinal columns. In cross-section each column is narrowest at the aqueductal surface and widens toward the outer surface. The surface abutting the AQU is lined by ependyma ( Paxinos-2012). The four columns are the dorsomedial periaqueductal gray, dorsolateral periaqueductal gray, lateral periaqueductal gray, and ventrolateral periaqueductal gray. Other substructures include the intercalated periaqueductal gray, supraoculomotor cap, pleioglia periaqueductal gray, and the nucleus of Darkshevich; some authors consider the supraoculomotor nucleus a component ( Paxinos-2001; Paxinos-2009a; Paxinos-2009b; Paxinos-2012 ). Authors differ as to whether these other structures are to be regarded as parts of the longitudinal columns or as independent structures ( Carrive-2012; Paxinos-2012 ). Functionally the periaqueductal gray belongs to the behavior control column of the motor system ( Swanson-2004 ) and the brainstem motor control system (BSM) of the motivational control system and the instinctive control system ( Bowden-2021). See also: motor periaqueductal gray. Updated 6 Nov 2025.

Also known as: periaqueductal gray matter, central gray substance of midbrain, central gray substance of the midbrain, Substantia grisea centralis mesencephali, Substantia grisea centralis, Griseum periventriculare mesencephali, Griseum centrale, Griseum centrale mesencephali, periaqueductal gray of tegmentum, Anulus aquaeductus, Anulus aqueductus cerebri, anulus of cerebral aqueduct, periaqueductal gray, central (periaqueductal) gray, PAG, central gray of the midbrain, central grey substance of midbrain

NeuroNames ID: 510

All Names & Sources

1 of 29

Showing 29 synonym(s) - Use arrows to navigate

Showing 29 synonym(s)

Name:

CGMB

Language:

acronym

Organism:

macaque

Source:

Martin-2000

Citation:

Elsevier, Amsterdam, 2000

Source Title:

Primate Brain Maps: Structure Of The Macaque Brain

Name:

graue Gebiete um den Zentralkanal

Language:

German

Organism:

human

Source:

Schiebler-1999

Citation:

Eighth Edition, Springer Verlag, Berlin, 1999.

Source Title:

Anatomie

Name:

zentrales Höhlengrau

Language:

German

Organism:

human

Source:

Mai-2002

Citation:

Zentrum für Anatomie und Hirnforschung, Institut für Neuroanatomie Heinrich Heine Universität, Düsseldorf, Deutschland

Source Title:

Name:

periaqueductal gray matter

Language:

English

Organism:

mouse

Source:

Hof-2000

Citation:

Elsevier, Amsterdam, 2000

Source Title:

Comparative Cytoarchitectonic Atlas of the C57BL/6 and 129/Sv Mouse Brains

Name:

zat-kelabu peri-akuadukt

Language:

Indonesian

Organism:

human

Source:

Noback-1982

Citation:

Jakarta: Penerbit Buku Kedokteran EGC, 1982

Source Title:

Anatomi Susunan Saraf Manusia, Prinsip-Prinsip Dasar Neurobiologi

Name:

central gray substance of midbrain

Language:

English

Organism:

human

Source:

Carpenter-1983

Citation:

Baltimore: Williams and Wilkins Co., 1983

Source Title:

Human Neuroanatomy

Name:

central gray substance of the midbrain

Language:

English

Organism:

Macaca fascicularis

Source:

Martin-1997

Citation:

Primate Information Center, University of Washington, Seattle, 1997.

Source Title:

Template Atlas of the Primate Brain

Name:

Substantia grisea centralis mesencephali

Language:

Latin

Organism:

human

Source:

Mai-1997

Citation:

San Diego: Academic Press, 1997

Source Title:

Atlas of the Human Brain

Name:

Substantia grisea centralis

Language:

Latin

Organism:

human

Source:

Riley-1943

Citation:

Baltimore: Williams and Wilkins Co., 1943

Source Title:

An Atlas Of The Basal Ganglia, Brain Stem And Spinal Cord (Based On Myelin-Stained Material)

Name:

Substantia grisea centralis

Language:

Latin

Organism:

Macaca fascicularis

Source:

Shantha-1968

Citation:

Baltimore: Williams and Wilkins, 1968

Source Title:

A Stereotaxic Atlas Of The Java Monkey Brain (Macaca irus)

Name:

Griseum periventriculare mesencephali

Language:

Latin

Organism:

Macaca fascicularis

Source:

Shantha-1968

Citation:

Baltimore: Williams and Wilkins, 1968

Source Title:

A Stereotaxic Atlas Of The Java Monkey Brain (Macaca irus)

Name:

Griseum centrale

Language:

Latin

Organism:

Macaca mulatta

Source:

Olszewski-1952

Citation:

S. Karger, Basel, Switzerland, 1952

Source Title:

The Thalamus Of The Macaca mulatta: An Atlas For Use With The Stereotaxic Instrument

Name:

Griseum centrale mesencephali

Language:

Latin

Organism:

human

Source:

Mai-1997

Citation:

San Diego: Academic Press, 1997

Source Title:

Atlas of the Human Brain

Name:

Griseum centrale mesencephali

Language:

Latin

Organism:

Macaca mulatta

Source:

Oertel-1969

Citation:

Journal fuer Hirnforschung 11: pp. 377-405, 1969

Source Title:

Zur zyto- und myeloarchitektonik des Rhombencephalon des Rhesusaffen (Macaca mulatta Zimmerman)

Name:

periaqueductal gray of tegmentum

Language:

English

Organism:

human

Source:

Carpenter-1983

Citation:

Baltimore: Williams and Wilkins Co., 1983

Source Title:

Human Neuroanatomy

Name:

periaqueductal gray matter

Language:

English

Organism:

human

Source:

Martin-1989

Citation:

Elsevier, New York, 1991

Source Title:

Neuroanatomy Text and Atlas

Name:

Anulus aquaeductus

Language:

Latin

Organism:

human

Source:

Riley-1943

Citation:

Baltimore: Williams and Wilkins Co., 1943

Source Title:

An Atlas Of The Basal Ganglia, Brain Stem And Spinal Cord (Based On Myelin-Stained Material)

Name:

Anulus aqueductus cerebri

Language:

Latin

Organism:

human

Source:

Roberts-1970

Citation:

Lea & Febiger, Philadelphia, 1970

Source Title:

Atlas Of The Human Brain In Section

Name:

anulus of cerebral aqueduct

Language:

English

Organism:

human

Source:

Roberts-1970

Citation:

Lea & Febiger, Philadelphia, 1970

Source Title:

Atlas Of The Human Brain In Section

Name:

periaqueductal gray

Language:

English

Organism:

human

Source:

Mai-1997

Citation:

San Diego: Academic Press, 1997

Source Title:

Atlas of the Human Brain

Name:

periaqueductal gray

Language:

English

Organism:

rat

Source:

Bowden-1997

Citation:

Source Title:

A digital Rosetta stone for primate brain terminology

Name:

central (periaqueductal) gray

Language:

English

Organism:

rat

Source:

Bowden-1997

Citation:

Source Title:

A digital Rosetta stone for primate brain terminology

Name:

центральное серое вещество

Language:

Russian

Organism:

human

Source:

Baev-2000

Citation:

Moskva: Meditsina, 2000.

Source Title:

Magnitno-Resonansnaia Tomografiia Golovnogo Mozga: Normal'naia Anatomiia

Name:

PAG

Language:

English

Organism:

rat

Source:

Swanson-1998

Citation:

Second Revised Edition, Elsevier Science, Amsterdam, 1998

Source Title:

Brain Maps: Structure of the Rat Brain

Name:

sostanza grigia periacquedutalle

Language:

Italian

Organism:

human

Source:

Carpenter-1995

Citation:

EdiSes, s.r.l.- Napoli, 1995

Source Title:

Fondamenti di Neuroanatomia

Name:

sostanza grigia centrale del mesencefalo

Language:

Italian

Organism:

human

Source:

Carpenter-1995

Citation:

EdiSes, s.r.l.- Napoli, 1995

Source Title:

Fondamenti di Neuroanatomia

Name:

substance grise périaqueducale

Language:

French

Organism:

human

Source:

Duvernoy-1992

Citation:

Springer-Verlag, Paris, 1992

Source Title:

Le cerveau humain: Surface, coupes seriees tridimensionnelles et IRM

Name:

central gray of the midbrain

Language:

English

Organism:

Unspecified

Source:

NeuroNames

Citation:

University of Washington, Seattle, WA

Source Title:

NeuroNames

Name:

central grey substance of midbrain

Language:

English

Organism:

human

Source:

AIBS-2011

Citation:

Allen Brain Atlas: Data Portal https://atlas.brain-map.org/

Source Title:

Allen Institute for Brain Science

Illustrations

Showing 5 illustration(s)

myelin stain & diagram of
all aspects in
human

labeled line drawings of
sagittal section in
Macaca fascicularis

multiple views of
3D reconstruction in
Macaca mulatta

Nissl stain & diagram of
sagittal section in
mouse

photomicrograph of
coronal section in
primate

Species With The Structure

Equivalent By	Human	Macaque	Rat	Mouse
Topology	Has The Structure	Has The Structure	Has The Structure	Has The Structure

1 of 19

Showing 19 record(s) - Use arrows to navigate

Showing 19 record(s)

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

Anulus aquaeductus

Source:

Riley-1943

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

Anulus aqueductus cerebri

Source:

Roberts-1970

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

anulus of cerebral aqueduct

Source:

Roberts-1970

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

central gray substance of midbrain

Source:

Carpenter-1983

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

Griseum centrale mesencephali

Source:

Mai-1997

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

periaqueductal gray

Source:

Mai-1997

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

periaqueductal gray matter

Source:

Martin-1989

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

periaqueductal gray of tegmentum

Source:

Carpenter-1983

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

Substantia grisea centralis

Source:

Riley-1943

Basis:

Topology

Has Equivalent:

Yes

Organism:

Homo sapiens (human)

Their Name:

Substantia grisea centralis mesencephali

Source:

Mai-1997

Basis:

Topology

Has Equivalent:

Yes

Organism:

Macaca fascicularis (Macaca fascicularis)

Their Name:

central gray substance of the midbrain

Source:

Martin-1997

Basis:

Topology

Has Equivalent:

Yes

Organism:

Macaca fascicularis (Macaca fascicularis)

Their Name:

Griseum periventriculare mesencephali

Source:

Shantha-1968

Basis:

Topology

Has Equivalent:

Yes

Organism:

Macaca fascicularis (Macaca fascicularis)

Their Name:

Substantia grisea centralis

Source:

Shantha-1968

Basis:

Topology

Has Equivalent:

Yes

Organism:

Macaca mulatta (Macaca mulatta)

Their Name:

Griseum centrale

Source:

Olszewski-1952

Basis:

Topology

Has Equivalent:

Yes

Organism:

Macaca mulatta (Macaca mulatta)

Their Name:

Griseum centrale mesencephali

Source:

Oertel-1969

Basis:

Topology

Has Equivalent:

Yes

Organism:

Rattus (rat)

Their Name:

central (periaqueductal) gray

Source:

Bowden-1997

Basis:

Topology

Has Equivalent:

Yes

Organism:

Rattus (rat)

Their Name:

PAG

Source:

Swanson-1998

Basis:

Topology

Has Equivalent:

Yes

Organism:

Rattus (rat)

Their Name:

periaqueductal gray

Source:

Bowden-1997

Basis:

Topology

Has Equivalent:

Yes

Organism:

Mus (mouse)

Their Name:

periaqueductal gray matter

Source:

Hof-2000

Models Where It Appears

Structural CNS Model - Macaque

Brain structures of the macaque are illustrated in BrainInfo’s NeuroMaps macaque brain atlas. Structures are grouped by proximity in a hierarchy corresponding to the central nervous system hierarchy of NeuroNames ( Bowden-1995 Martin-2000 ). Structures in the NeuroMaps atlas are based on the segmentation of an MRI of the brain of a 3-year old male rhesus macaque (Macaca mulatta). The atlas is most useful for targeting structures for implantating electrodes and chemtrodes. Updated 29 Oct 2025.

cerebral crus (crus cerebri)

hindbrain

choroidal fissure