How does light intensity affect the size of a frog optic nerve fibre’s receptive field?

In the physiology of the frog, the size of a receptive field associated with a single optic nerve fibre is not fixed; rather, it varies depending on the intensity of the light stimulus.1

Research indicates that the receptive field is largest when the stimulus is strongest. Consequently, for a light stimulus falling at a distance from the centre of the field to successfully activate that specific fibre, it must be significantly more intense than a stimulus falling directly on the centre. This variation in size suggests that certain synaptic pathways within the retina are more favoured than others, allowing the visual system to adjust its sensitivity based on the strength of the incoming light.1