Physio 10: Vision

Vision feels immediate and authoritative, yet what we experience as “seeing” is not a direct recording of reality. It is a carefully reconstructed narrative, assembled from photons, probabilities, and prior expectations.In this episode, Medlock Holmes investigates the physiology of vision—from phototransduction in the retina to signal processing along visual pathways. We explore how rods and cones translate light into electrical signals, how contrast and movement are prioritised over absolute brightness, and how the visual system extracts meaning rather than detail.This episode emphasises that vision is not about creating a perfect image of the world. It is about creating a useful representation—one that supports navigation, recognition, and survival.Here, physiology reminds us that sight is not passive reception.It is active interpretation.Key Takeaways* Vision begins with phototransduction, not perception* Rods and cones specialise for sensitivity and colour discrimination* Retinal circuits enhance contrast and edges before signals reach the brain* Visual pathways segregate information by function (motion, form, colour)* What we “see” reflects interpretation as much as input This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit drmanaankarray.substack.com/subscribe