On-centre, off-surround and off-centre, on-surround receptive field

Figure 6a
(Photograph taken from Discovering Biological Psychology on-line video)

The eyes see objects and defines boundaries and edges through the firing of the ganglion cells in the receptive fields. In figure 6a, the on-centre, off-surround array of receptor cells is activated when bright light is shone of the on-centre, the firing rate is rapid and when the surround is lighted, the the ganglion cells fire at a moderate rate. Our visual system responds to edges in objects in this say. The LGN generates a signal to the visual cortex and sees the edge at a specific angle.