Orientation biased extended surround of the receptive field of cat retinal ganglion cells.

Here we report that the extended surround outside the classical receptive center (hereafter called the extended surround) of most retinal ganglion cells in the cat exhibit significant orientation bias to grating stimuli, and that the center and the extended surround show different orientation biases at different spatial frequencies. As a result, some retinal ganglion cells possess a complex receptive field structure, which allows them to detect sophisticated image segmentation (e.g. texture segmentation) in addition to simple luminance edges. This property was previously thought to exist primarily in the visual cortex. Moreover, in about one quarter of 128 cells studied the center did not exhibit an orientation bias. Thus, these surrounds alone may determine the cells' orientation bias.In conclusion, the extended surround may play an important role in processing more complex pattern in natural scenes since the classical receptive field is too small to describe all the properties of a retinal ganglion cell.