Gate Control Theory and the Brain

Gate Control Theory

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In order to explain why our mental states impact pain perceptions, researchers Ronald Melzack and Patrick Wall proposed what is known as gate control theory during the early 1960s. This theory suggests that the spinal cord contains a neurological "gate" that either blocks pain signals or allows them to continue on to the brain.

Researchers have long observed that factors such as thoughts, emotions, and expectations can influence our perceptions of pain. If you expect something to hurt, it probably will hurt worse. If you are upset or frightened, pain may seem more intense than it would if you were calm.

Unlike an actual gate, which opens and closes to allow things to pass through, the "gate" in the spinal cord operates by differentiating between the types of fibers carrying pain signals. Pain signals traveling via small nerve fibers are allowed to pass through while signals sent by large nerve fibers are blocked. Gate control theory is often used to explain the phantom or chronic pain.

How Gate Control Works

Following an injury, pain signals are transmitted to the spinal cord and then up to the brain. Melzack and Wall suggest that before the information is transmitted to the brain, the pain messages encounter "nerve gates" that control whether these signals are allowed to pass through to the brain.

In some cases, the signals are passed along more readily and pain is experienced more intensely. In other instances, pain messages are minimized or even prevented from reaching the brain at all.

A Closer Look at the Gate Control Process

This gating mechanism takes place in the dorsal horn of the body's spinal cord. Both small nerve fibers (pain fibers) and large nerve fibers (normal fibers for touch, pressure, and other skin senses) both carry information to two areas of the dorsal horn.

These two areas are either the transmission cells that carry information up to the spinal cord to the brain or the inhibitory interneurons which halt or impede the transmission of sensory information.

  • Large fiber activity, however, excites the inhibitory neurons, which diminishes the transmission of pain information. When there is more large fiber activity in comparison to pain fiber activity, people tend to experience less pain. This means that the pain gates are closed.
  • Pain fibers impede the inhibitory interneurons, allowing pain information to travel up to the brain. When there is more small fiber activity, it inactivates the inhibitory neurons so that pain signals can be sent to the brain in order for pain perception (also known as nociception) to take place. In other words, the pain gates are now open.

While it is perhaps the most influential theory of pain perception, gate control is not without problems. Many of the ideas suggested by Melzack and Wall have not been substantiated by research, including the very existence of an actual gating system in the spinal cord. 

Gate Control Explains Why Touch Can Modulate Pain Perception

Melzack and Wall suggest that this process explains why we tend to rub injuries after they happen. When you bang your shin on a chair or table, for example, you might stop to rub the injured spot for a few moments. The increase in normal touch sensory information helps inhibit pain fiber activity, therefore reducing the perception of pain.

Gate control theory is also often used to explain why massage and touch can be helpful pain management strategies during childbirth. Because the touch increases large fiber activity, it has an inhibitory effect on pain signals.

Melzack and Wall themselves noted that the "gate" metaphor for pain perception served as a helpful way of helping people understand the basic concept, regardless of whether they grasped the complex physiological processes behind the theory. Doctors often utilize the gate metaphor to help patients understand how and why pain can fluctuate so much.

A Word From Verywell

While gate control theory does not explain every aspect of how people experience pain, it does tell us some important things. Melzack and Wall's theory was the first to consider the psychological factors that influence the perception and experience of pain.

There was initially a period of resistance to the theory after the original article was published, but it soon became accepted as evidence increasingly pointed to the existence of a spinal gating mechanism. The theory helped transform approaches to the treatment of management of pain.

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Article Sources

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  • Melzack R, & Wall PD. Pain mechanisms: a new theory. Science (New York, N.Y.). 1965;150(3699):971-9 PMID: 5320816