How can stimuli outside a classical receptive field affect a neuron’s response?

Stimuli located outside the classical receptive field—often referred to as the nonclassical receptive field, silent surround, or modulatory surround—cannot typically evoke a neuronal response on their own. However, they play a significant role in sensory processing by modulating or adding to the responses driven by the more sensitive central portion of the receptive field.1

In general, these peripheral stimuli are either inhibitory or subthreshold. Researchers identify these regions by pairing stimuli within the classical receptive field with stimuli in the surrounding area. This interaction can result in summation, where responses increase over a region larger than the classical receptive field, known as the summation area or summation field.1

Ultimately, the broader definition of a receptive field encompasses both the classical region, where stimuli directly trigger changes in firing, and the nonclassical region, where stimuli modulate those responses.1