Schematic of the model . The retina is represented via two layers (ON and OFF) of retinal ganglion X-cells. The thalamic subsystem consists of several layers: two layers (ON and OFF) of thalamic relay cells together with local thalamic interneurons and one layer of thalamic reticular nucleus (RTN) neurons. The V1 module contains four layers of primary visual cortex (layers 4, 2/3, 5 and 6), modeled after a restricted portion of cat striate cortex (area 17). Red arrows denote the major feed-forward excitation flow in the model. Blue arrows show the direction of major feedback from the cortex to the thalamus.