Observations on the 'surround' properties of the receptive fields of frog retinal ganglion cells.

The activity of frog retinal ganglion cells has been studied, using metal filled micropipette electrodes and recording the activity in either the optic nerve or the superficial neuropil of the optic tectum. It is a feature common to all such cells that their activity can be modulated by retinal stimulation of an area surrounding the excitatory receptive field (ERF). It has been demonstrated that the inhibitory ‘surround’ for sustained edge units (class 1 and 2) is considerably larger than previously realized, extending up to 45° from the edge of the ERF. An inhibitory surround to the receptive fields of ‘on’ units has been demonstrated. In addition an unsuspected complexity of the surround organization of dimmer units (class 4) has been found.