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Last updated: Mon, Mar 3, 2025
The periaqueductal gray or PAG receives input from the anterior cingulate cortex (ACC), the insular cortex (IC), the hypothalamus, and from the amygdala. The amygdala in turn receives input from various areas of the cortex and it receives ascending nociceptive input from the spinal cord.
Both the PAG and the RVM receive ascending nociceptive inputs through the old slow/aching tract of the STT and through other ascending tracts. The PAG is able to integrate input from the spine, the thalamus and hypothalamus, and the limbic areas of the brain.
The primary descending output of the periaqueductal gray, PAG, goes to the rostral ventromedial medulla or RVM. Ascending output from the PAG flows to the thalamus, the hypothalamus, and the frontal cortex. The functions of these ascending connections are currently unknown.1 Output from the PAG to the basal ganglia is probably involved in autonomic regulation.