Periaqueductal gray matter

Periaqueductal gray matter (PAG) is a structure located around the cerebral aqueduct within the tegmentum of the midbrain. It plays a crucial role in the modulation of pain and in defensive and reproductive behaviors.

Anatomy

The periaqueductal gray is so named because it is gray matter situated around the cerebral aqueduct. This structure is divided into four columns: the dorsal, lateral, ventrolateral, and ventral columns. Each column has a different function and projects to different areas of the brain.

Function

The PAG plays a role in many functions, including pain modulation, defensive behavior, reproductive behavior, and cardiovascular control. It is also involved in the body's response to stress and panic.

Pain modulation

The PAG is a major component of the descending pain modulation system. It receives inputs from the cortex, hypothalamus, and amygdala, and sends outputs to the rostral ventromedial medulla (RVM) and the spinal cord. Activation of the PAG can produce powerful analgesia.

Defensive behavior

The PAG is involved in defensive behaviors such as freezing and flight. It receives inputs from the amygdala, which is involved in fear conditioning, and sends outputs to areas of the brainstem that control cardiovascular and respiratory responses to stress.

Reproductive behavior

The PAG is involved in reproductive behaviors such as mating and parental care. It receives inputs from the medial preoptic area and sends outputs to the ventromedial hypothalamus and other areas involved in these behaviors.

Clinical significance

The PAG is a target for deep brain stimulation in the treatment of chronic pain conditions. It is also implicated in panic disorder and post-traumatic stress disorder.

See also

• Cerebral aqueduct
• Midbrain
• Pain modulation
• Defensive behavior
• Reproductive behavior

References

Periaqueductal gray matter Resources
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