How do action potentials reveal whether a sensory neuron has responded to a stimulus?

In the context of sensory physiology, action potentials—often referred to as "spikes"—serve as the primary indicator that a sensory neuron has responded to a stimulus.1

A sensory neuron's response is revealed when the presentation of a stimulus within its receptive field causes a deviation in the neuron's discharge rate away from its baseline, or background, activity level. Specifically, researchers identify a response by observing:1

• Increased Firing: An increase in the frequency of action potentials indicates that the stimulus has successfully excited the neuron.1
• Inhibitory Effects: Conversely, a decrease in firing or the suppression of activity can reveal that a stimulus has triggered an inhibitory response, which is common in regions exhibiting centre-surround antagonism.1

By monitoring these changes in action potential discharge, physiologists can map the spatial extent and functional properties of a neuron's receptive field, determining which specific stimuli or locations are capable of eliciting a neural impulse.1