08a vision processing intorduction

Visual receptor

Neuronal architecture of mammalian visual system

Retina

Photoreceptors Rod and Cone

Anatomical Distribution of Rods and Cones

Phototransduction

Phototransduction

LightDark

Retina Functional organization

1. Retinal cell types

2. Neural Circuitry of Retina

3. Hyperpolarization

4. Neurotransmitters

5. Electrical synapse with graded conduction

6. Lateral inhibition

7. Bipolar cell depolarization/ hyperpolarization

Receptive Field

An experimental plan for recording from the visual pathway. The animal, usually a macaque monkey, faces a screen onto which we project a stimulus. We record by inserting a microlectrode into some part of the pathway, in this case, the primary visual cortex. (The brain in this diagram is from a human, but a monkey brain is very similar.)

Receptive field of Retina

Receptive Field

Receptive fields of photoreceptors and their connections. (A) The receptive field center provides a direct input from the photoreceptors to the bipolar cell, and the receptive field surround provides indirect input from the photoreceptor to the bipolar cells via horizontal cells. (B) 1: Photoreceptor cell; 2: on-center bipolar cell; 3: off-center bipolar cell; 4: on-center ganglion cell; 5: off-center ganglion cell.

Receptive field of two ganglion cells overlap

Two neighboring retinal ganglion cells receive input over the direct path from two overlapping groups of receptors. The areas of retina occupied by these receptors make up their receptive-field centers, shown face on by the large overlapping circles.

Dimension of Receptive field

One millimeter on the retina corresponds to 3.5 degrees of visual angle. On a screen1.5 meters away, 1 millimeter on the retina thus corresponds to about 3.5 inches, or 89 millimeters.

Receptive field

Responses of retinal bipolar and ganglion cells to darkness and illumination in the receptive field center.A) Changes in the electrical activity of the photoreceptor and on- and off-center bipolar and ganglion cells when the photoreceptor receptive field center is in the dark. (B) Changes in the electrical activity of the photoreceptor and on- and off-center bipolar and ganglion cells when the photoreceptor receptive field center is illuminated

Lateral inhibition mechanism

Responses of retinal bipolar and ganglion cells to darkness and illumination in the receptive field surround. (A) Changes in the electrical activity of the photoreceptor and on- and off-center bipolar and ganglion cells when the photoreceptor receptive field surround is in the dark. (B) Changes in the electrical activity of the photoreceptor and on- and off-center bipolar and ganglion cells when the photoreceptor receptive field surround is illuminated.

Receptive Field: Ganglion Cells

Stimulus M Cells P Cells

Color No Yes

Contrast High Low

Spatial Low High

Temporal High Low

Ganglion Cell : Contrast discrimination

Central Projections of Retinal Ganglion Cells

Lateral Geniculate Nucleus

Lateral Geniculate Ganglia

Pupillary reflex

Organization of Visual Cortex

Extrastriate Visual Areas Macaque Monkey

Human Visual Cortex fMRI

Visual Cortex Architecture

Visual Cortex Architecture

Recording from Visual Cortex

Simple cell of visual cortex

Simple Cell

Complex cell

Complex Cell

Complex Cells

Hypercomplex Cells

Significance of Movement Cells

Orientation Column

Orientation column of visual cortex

Illusion of Edges: V2 in Monkey

Inferior Temporal neuron response to Form

Illusion of Edges: V2 in Monkey

Face and Complex Form Recognition ITC

Blobs

40μm thick layer of upper cortex that has been processed histochemically to reveal the density of cytochrome oxidase, a mitochondrial enzyme involved in energy production

Ocular dominance column

Visual Cortex Architecture

AIT = anterior inferior temporal area; CIT = central inferior temporal area; LIP = lateral intraparietal area; Magno = magnocellular layers of the lateral geniculate nucleus; MST = medial superior temporal area; MT = middle temporal area; Parvo = parvocellular layers of the lateral geniculate nucleus; PIT = posterior inferior temporal area; VIP = ventral intraparietal area.) (Based on Merigan and Maunsell 1993.)

Motion in the visual field

PET scan of MT area for Motion Processing

Depth of vision

Neuronal basis of stereoscopic vision

AIT = anterior inferior temporal area; CIT = central inferior temporal area; LIP = lateral intraparietal area; Magno = magnocellular layers of the lateral geniculate nucleus; MST = medial superior temporal area; MT = middle temporal area; Parvo = parvocellular layers of the lateral geniculate nucleus; PIT = posterior inferior temporal area; VIP = ventral intraparietal area.) (Based on Merigan and Maunsell 1993.)

MT lesions in Monkey and Man with altered Motion Perception

Inferior Temporal neuron response to Color & Form

Color Vision

Cones and Color Vision

Surface reflectance

Surface reflected from blue vase in sunlight and skylight

The reflectance function of a natural surface

L+M

L-M

L+M-S

Receptive field of Primate Ganglion Cells for Color

The Importance of Context in Color Perception

Color blindness

Normal Protanope

Deuteranope Tritanope

Ishihara Chart for Color blindness testing

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