Background

Nociceptors in the skin detect damage or trauma at the skin and transmit that information up the spinothalamic pathway. However, there is also a downward pathway, leading from higher centers in the brain and heading down into the spinal column. The information coming from the brain can inhibit the flow of information upward toward the brain from the nociceptors. When it does so, the experience of pain is inhibited. In addition to signals from the brain, pain signals can be reduced by simulation through the touch channels, the dorosal column-medial leminiscal pathway.

This view of pain perception has been called the gate control theory (Melzack & Wall, 1988). We also know where gate control occurs. The nociceptors first synapse in the spinal cord in an area called the substantia gelatinosa of the dorsal horn. It is here that neural signals from the brain and the touch pathways can inhibit the upward flow of pain information.

Use this activity to explore the basic functioning of the cate control theory.

Instructions

Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab

On the Illustration tab, interact with the gate control theory.

Settings

Below is a list of the ways that you can alter the illustration. The settings include the following:

Descending Input: the strength of the input from the brain inhibiting the pain information.
Large Fiber Input: the strength of the touch input that will travel up the dorsal column-medial lemniscal pathway. These are large diameter neurons.
Small Fiber Input: the strength of the input from the nociceptor. This information travels in small diameter fibers.

Reset

Pressing this button restores the settings to their default values.