Pain at the Door? Ask Your Spinal Cord's Gatekeeper First

Pain is a universal experience that affects human lives, but have you ever wondered why some pain feels more intense than others or why rubbing a sore area can sometimes ease the discomfort? Let us learn what causes this.

Descartes said pain is produced by a direct, straight transmission system from injured tissues in the body to a pain center in the brain. This theory dominated pain studies and therapy till 1965 when Melzack proposed an alternative.

The Pain Gate Theory proposed by Ronald Melzack and Patrick Wall in 1965, explains how our nervous system processes and modulates pain.

The Pain Gate Theory suggests that pain is not solely a result of physical injury but is also influenced by how our nervous system interprets and modulates signals. According to this theory, a "gate" mechanism in the spinal cord blocks or allows pain signals to travel to the brain.

The dorsal horns of the spinal cord function like a gate, either inhibiting or facilitating the transmission of signals from the body to the brain. This process is influenced by the diameter of the active peripheral fibers carrying sensations and the dynamic interplay between peripheral and central nervous system actions.

Large nerve fibers help us feel touch and pressure while small nerve fibers help us feel pain and temperature. The large fibers quickly convey information while the small fibers are slow.

Psychological factors, including past experiences, attention, and other cognitive activities, play a crucial role and have been integrated into contemporary research and theories on pain perception and modulation.

Pain signals originate in the nerves of injured or affected tissues and travel to the spinal cord and the brain. However, this process is regulated by the "gate," located in the dorsal horn of the spinal cord.

• Open Gate (Increased Pain):
  When the gate is open pain signals pass through more easily, resulting in a higher perception of pain. This can occur during stress, heightened emotions, or when other sensory input is minimal.

• Closed Gate (Decreased Pain):
  When the gate is closed, fewer pain signals reach the brain, reducing pain perception. Distractions, positive emotions, or competing sensory inputs, like pressure or vibration influence it.

We have all been managing pain in various ways without too much thought. Let us hear what Dr. Arvind Bhateja, a neurosurgeon has to say about the practical applications.

Pain Management Techniques:

TENS (Transcutaneous Electrical Nerve Stimulation):

Electrical stimulation of the skin activates non-painful sensory signals, helping to "close the gate."

Massage and Rubbing:
Stimulates larger nerve fibers, reducing the sensation of pain.

Mindfulness and Relaxation:

Techniques like meditation and deep breathing reduce stress, help to close the gate and minimize pain perception.

Distraction Methods:

Engaging in enjoyable activities or listening to music diverts attention from pain.

• Physical Factors:

  The intensity of the pain stimulus.

  Competing sensory signals (e.g., rubbing the affected area).

• Emotional Factors:

  Stress and anxiety open the gate.

  Relaxation and positive emotions close it.

• Cognitive Factors:

  Attention to pain intensifies it.

  Distraction or focusing on non-painful activities reduces it.

The Pain Gate Theory highlights the complex interplay between physical, emotional, and cognitive factors in pain perception. Understanding how this "gate" works, can help us manage pain better using various techniques, from physical therapies to mindfulness.

While the Pain Gate Theory was revolutionary, it did not explain all aspects of pain, such as chronic pain conditions without apparent physical stimuli. Modern research incorporates neurochemical processes and brain activity, further enriching our understanding of pain.

References:

1. Melzack, Ronald. “Gate Control Theory: On the Evolution of Pain Concepts.” Pain Forum 5, no. 2 (June 1, 1996): 128–38. https://doi.org/10.1016/S1082-3174(96)80050-X.

2.Braz, João, Carlos Solorzano, Xidao Wang, and Allan I. Basbaum. “Transmitting Pain and Itch Messages: A Contemporary View of the Spinal Cord Circuits That Generate Gate Control.” Neuron 82, no. 3 (May 7, 2014): 522–36. https://doi.org/10.1016/j.neuron.2014.01.018.

3. https://www.physio-pedia.com/Gate_Control_Theory_of_Pain

By Dr. Swati Sharma