What happens in a centre-surround receptive field when the centre is stimulated?

In a centre-surround receptive field, the response to stimulation depends on the specific organization of the neuron:

• On-centre units: When a spot of light stimulates the centre of the receptive field, the neuron produces an "on-response," which typically manifests as an increase in the frequency of action potentials or an increase in the background discharge rate.123
• Off-centre units: When the centre is stimulated with light, these neurons exhibit the opposite effect, typically showing an inhibition of their background discharge.12

This organization is a manifestation of centre-surround antagonism, where the centre and the surrounding region of the receptive field elicit opposite responses. This mechanism, often associated with lateral inhibition, allows the visual system to emphasize contrast and edges rather than responding to uniform illumination.415