Definition of "periaqueductal" []

• Situated around the aqueduct of the brain: the periaqueductal gray matter. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "However, as the predator moved closer, the brain activity shifted to a region of the brain responsible for more primitive behaviour, namely the periaqueductal grey."
• "One example is the region known as the periaqueductal gray PAG, which is a major coordinator of emotional responses."
• "One important reason breathing affects mood and pain is because of its impact upon a part of the brain known as the periaqueductal gray area, or PAG."