(Note this is part 1 of a 2 part series of posts on Visual Processing)
To explore the possibility of a Visual BCI (VBCI) we need to discuss how the human visual processing system works. In early embryotic stages, what will become the retina is indistinguishable from other parts of the proto brain. During retrogenisis a protrusion develops out of the neural tissue that eventually separates and becomes the eye.[i] The rods, cones and ganglion cells of the retina are neurons.
As light stimulates rod and cone cells they send signals to their ganglion cells, which in turn transmit to the optic nerve and on to the main corpus of the brain. The optic nerve delivers the signals to the visual cortex, which is divided into many cortical areas each specialized in processing particular types of visual information.
It is important to note that the human brain dedicates a very large amount of real estate to visual processing. Nearly one third of the surface of the cortex is used exclusively for vision. About two thirds of the volume of the entire brain are in some way used by the visual processing system.[ii] Some neurons are multimodal and made use of by other functional specialized networks within the brain. Through these there is a pathway from visual input to areas of the brain that are not directly involved in vision.
Just like in the Dynamic Core and the other processes that contribute to it, the visual processing system has reentrant interconnections between individual visual cortices that feed forward into each other, slightly modifying the functionality of each other with every cycle. The state of your perception directly affects what you perceive. When one discerns an optical illusion that can be interpreted in two different ways, once one way is perceived it becomes more likely to continue to be perceived.
[i] Ikuo K. Suzuki1 and Pierre Vanderhaeghen, Is this a brain which I see before me? Modeling human neural development with pluripotent stem cells (The Company of Biologists Ltd, Development 142, doi:10.1242/dev.120568, 2015) 3145.
[ii] Valentin Dragoi, Visual Processing: Cortical Pathways (Neuroscience Online) http://neuroscience.uth.tmc.edu/s2/chapter15.html.