For example, look at this photo, and then you will obviously see some lines that are between the neighboring bands here. Actually, for this individual band here they are uniform from the intensity [FOREIGN]. Why actually, on this edge, do you have so like a huge contrast? You will see a line there. There is actually no line. So with this, then we can connect with the receptive field center surround. Let's take a look. So for example, if you have a ganglion cell in which the receptive field, it's a center surround. Center is on, for example, surround is off. So if the ganglion cell receptive field is covered by one band, ahatever happened to ganglion cell? This ganglion cell, of course right now, you don't have strong stimulation, and also canceled, surround the center. The cell would be quite especially quiet. But then when you move this cell to the left, yeah, to your right side. And if the cell moves to this region, let's see what happens. For example, B is the same thing, right? You're perceiving the more kind of bright band. Because the cancellation contains a surround and a center, the cell is quite silent. And also, if we move this cell to this region, you can see right now, the center actually get a lot of stimulation by this bright light here. And the surround, of course you also get a sound stimulation from this region. But this region, actually you don't have stimulation. Okay, we talk about actually the center surround is almost cancelling each other. If we have complete, like this situation, then you don't have the activity. But here, actually this cell is most strongly excited, because under this situation, and then this is strong response. But the surrounding, you cannot have a full cancellation, because in this region you don't have stimulation. If you move to this region, what would happen? And then this node excitation. But then this actually have the inhibition. So, in this case, this is very strong. You just, the center, just sitting on the edge of the band, then you will have a strong excitation. Then you see straight lines. So this is the information processing, actually in the retina. And the one very important feature about the processing is center surround receptive field. And the center surround receptive field also related to the on off pathway. So in the retina, actually, we use our eye to look at the visual information. Actually, you need to get a lot of information. For example, color and brightness and also the shape and also maybe some other features. So, all these features, you need go to the brain, and then you can really make a complete perception. So, in the retina, we talk about actually, okay, this is on, off pathway. And also, there is some kind of color pathway generated in the retina. So this pathway, in most case actually, they are parallel. [FOREIGN] So you have so many different channels to process the information like a motion and color and on, off brightness signal. So this information, you need processing the brain. Let's take a look actually, what's the visual pathway in the brain? This is the light information will go from the eye, retina, then go to the first brain center, it's called lateral geniculate nucleus, LGN. Translate into Chinese it's [FOREIGN]. [FOREIGN] And then the information from the LGN. And then we'll further transfer to the primary visual center. Racial context, okay
