The Human Visual System Short Overview
Terms: LGN, cortex, primary visual cortex, V1
Each half of the visual field goes to a different hemisphere of the brain
Hemifield neglect
Eye Terms: Retina, fovea
Layers of the retina Terms: photoreceptors, ganglion cells
Receptors Density - Fovea
Rods and Cones
Image Capture Huge dynamic range – μW/cm 2 Photons: poisson process. Noisy at low levels For low light: large receptors, slow integration Rods/cones, local adaptation,change of amplitude and time constant, motion deblur
Dynamic Range
Visual receptor types
Photo transduction: retinal + opsin
Retina Mosaic
Color Mixing
Neural circuitry of the retina
Center-surround Receptive Fields Modified from PSY280F
Retina Output: Ganglion Receptive Fields
Visual Areas
Physiological Recording
Recording from a Neuron
Orientation Selectivity
V1: Direction selectivity Modified from PSY280F
Orientation Map, Optical Recording
Contours and Boundaries (V1, V2)
Rotated Subjective Disk
Neon Spreading
Stimuli tested in V2, V4
Seeing without awareness OR:
From pixels to perception Large part of the brain Much of prior to awareness