How do on-fibres, off-fibres, and on-off fibres differ in the frog retina?

In the frog retina, studies of single optic nerve fibres have identified three distinct types of responses based on how they react to light stimuli within their receptive field:

• On-fibres: These fibres remain inactive during darkness but produce a discharge of electrical impulses when a light stimulus is switched on.
• Off-fibres: These fibres remain inactive during illumination but generate a powerful discharge when the light stimulus is switched off.
• On-off fibres: These fibres are inactive during the period of steady illumination; instead, they produce discharges at both the onset ("on") and the cessation ("off") of the light stimulus.

Each of these fibres corresponds to a specific area of the retina, and the size of this receptive field can vary depending on the intensity of the light stimulus used, with stronger stimuli activating larger areas of the retina.1