That Neuroscience Guy Vision Part 1- The Dorsal Stream
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May 2, 2021 A tour of how sight becomes action-ready information. Short explanations of rods and cones, midbrain orienting centers, and V1 as a pixel map. How early visual areas build edges, depth, shape and color. Deep dive into motion processing in area MT and disorders that reveal its role. Exploration of the dorsal pathway that maps space for reaching and subconscious corrections.
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Primary Visual Cortex Creates A Cortical 'Picture'
- Vision begins with photons hitting rods and cones that 'turn on' like pixels on a screen.
- Olaf Kregolson explains V1 is a cortical copy of the eye's image where ~140 million neurons detect edges and lines as the first processing step.
Visual Areas Gradually Build Shape Color And Motion
- Visual processing builds complexity through sequential areas V2 to V4, converting 2D retinal input into 3D shapes, color, and object representations.
- Olaf notes V3 extracts basic shapes, V4 adds color, and MT integrates snapshots to infer motion.
Dorsal Stream Computes Subconscious Spatial Maps
- The dorsal stream routes visual information from early visual areas to the posterior parietal cortex for spatial computations used in action.
- Olaf describes this as a subconscious system calculating precise distances and positions without adding object meaning.