The Human Visual System • Background on Vision • Human vision – the best system around • Deep network models
Hemifield neglect
Eye
Recording Spikes
Receptors Density - Fovea
Image Capture • • • Huge dynamic range 10 -8 – 10+6 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
Poisson Distribution
Adaptation Effect
Dynamic Range
Visual receptor types
Retina Mosaic
Color Mixing
Retina Output: Ganglion Receptive Fields Output = image * Do. G
Cortex
Bi-directional Computation
Physiological Recording
Orientation Selectivity
V 1: Direction selectivity Modified from PSY 280 F
Visual Areas
Contours and Boundaries (V 1, V 2)
Stimuli tested in V 2, V 4
Neuronal Responses, V 2
Stimuli tested in V 2, V 4 Models (SIFT, Ho. G) do not represent such features
Tanaka IT clusters Kiani, et al J. Neurophysiol 2007 Object Category Structure in Response Patterns of Neuronal Population in Monkey Inferior Temporal Cortex.
f. MRI Magnet
f. MRI Activation Slice
f. MRI Activation
(Fusiform (red, yellow
Face-Pace Rivalry
House-Face f. MRI Transitions Rivalry differences similar to monocular but less pronounced Activity is higher for the perceived stimulus Dominance is partial, significant activity for the non-dominant stimulus.
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