Human brain: with 100 billion cells, each with 7,000 to 10,000 connections.

Research demonstrates that human infants perceive pain, as determined by physiological and behavioral responses, at their earliest developmental stages, even before birth.

A critically important question is: What are the lasting consequences of the early experience of pain? Emerging evidence indicates that neonatal pain can have profound and perhaps permanent effects on development. For example, premature babies receiving painful clinical procedures during intensive care later exhibited a lower reaction to pain. In fact, there was a strong correlation between the number of painful procedures and the resulting reduction in pain sensitivity.

At the March 24 event we will discuss animal research that shows that experience of pain during an early stage of development known as the "sensitive or critical period" permanently alters pain perception in the adult in a manner remarkably similar to that in humans. These studies further show that pain during the critical period permanently changes the way neural pathways and circuits in the brain are organized.

Such studies have only scratched the surface as the human brain is bewilderingly complex, with 100 billion cells, each with 7,000 to 10,000 connections. Further research using modern techniques to map and visualize neurons and their connections will be needed to reveal all the effects of neonatal pain on the brain and behavior.

http://www.commercialappeal.com/news/2011/mar/12/guest-column-early-experience-of-pain-has/