How does the brain interpret the intensity of a stimulus?

The brain interprets the intensity of a stimulus primarily by the frequency of action potentials generated by sensory neurons. In the nervous system, when a stimulus is perceived, it creates a change in the membrane potential of sensory receptors, leading to the generation of action potentials. The intensity of the stimulus affects how often these action potentials are fired: a stronger stimulus will lead to a higher frequency of action potentials.

This frequency coding is fundamental because the brain uses the rate of incoming signals to determine how intense a stimulus is. For example, touching a hot surface produces a strong stimulus resulting in more frequent action potentials compared to a gentle touch.

While the involvement of the number of sensory neurons activated is important in conveying information about the overall intensity of a stimulus, the primary mechanism for distinguishing varying intensities relies on the frequency of the action potentials from a single neuron or multiple neurons.