Components of the visual system

The individual neuron

Neuron

Neurons

Purkinje cells from cerebellum, dendrites showing calcium concentration

Synaptic connection

Synapse

The Eye

The main aspects are the photoreceptors, which is the input layer, and the ganglion cells, the output layer to the brain

Eye

Neural circuitry of the retina

Receptors Density - Fovea

Photoreceptors

Photoreceptors

Visual receptor types

Spectral sensitivity

Color Mixing

Dynamic Range

Center-surround Receptive Fields

Modified from PSY280F

Edge-detection by zero-crossings

Some theory, and the relation to ganglion cells .

Edge Detection by Z.C.

Peak in f’(x) z.c. in f’’(x) Noise: Asin(wx) > -w2cos(wx) Convolve with a Gaussian (optimal) d2/dx2(G*f) = d2/dx2(G) * f

In 2-D: d2/dx2 + d2/dy2

Edge Detection by Z.C.

Z.C. at Two Scales

Wheel Edges 4 Resolutions

LGN Layers

The Cortex

The main topics are: area V1 in some details, response properties of cells in V1, how they are

organized in the area .General properties of higher level visual areas .

Physiological Recording

Orientation Selectivity

V1: Direction selectivity

Modified from PSY280F

End-stopped cell

Simple Cells

Visual Areas

Bi-directional Computation

Stimuli tested in V2, V4

From: Tanaka, 1996

Columnar modules of region TE

fMRI Magnet

fMRI Activation Slice

fMRI Activation