How did Horace Barlow and Stephen Kuffler expand the definition of a retinal receptive field?

In 1953, Horace Barlow and Stephen Kuffler expanded the definition of a retinal receptive field beyond the initial criteria established by Haldan Keffer Hartline.

While Hartline had originally defined the receptive field of a retinal ganglion cell as the specific area of the retina where light stimuli could elicit an increase in the frequency of action potentials, Barlow and Kuffler broadened this scope. They extended the definition to include all retinal areas within which stimulation could either excite or inhibit the ganglion cell's response.1

This shift recognized that receptive fields are not merely regions of excitation but are complex structures capable of both activating and suppressing neuronal activity, a concept fundamental to understanding phenomena such as centre-surround antagonism and lateral inhibition.12