Day 1: How does the brain begin processing vision? — Understanding the Visual Cortex

Goal: understand the human visual cortex — the brain is the original inspiration for computer vision
Image processing in the brain begins at the Primary Visual Cortex, which splits into two streams
Dorsal stream (the "where" pathway) — answers "where is this thing?" and "what do I do about it?" — extremely fast
Ventral stream (the "what" pathway) — identifies objects via color, texture, shape — takes longer to process
The retina has two types of output cells: M-cells (fast) and P-cells (slow) — this is why one stream is faster than the other
Dorsal stream works with M-cells, which are designed to detect changes in the scene — it starts at the retina itself
MT area (Middle Temporal) is where motion is tracked and changes in the image are processed
PPC (Posterior Parietal Cortex) is the GPS of the brain — builds a spatial map of the world: distance, speed, relative position
PPC splits its output into action (reaching, grasping, dodging) and gaze (where to move eyes next, via motor/pre-motor cortex)
Dorsal stream operates in real-time and has no memory — picking up a pen triggers automatic computation of pressure & depth before conscious awareness