The visual and oculomotor systems Peter H. Schiller, year 2006

Review,the visual and oculomotor systems

Basic wiring of the visual system

or

left h

e

fix

Primates

Horopter (Vieth-Muller circle)

temporal nasal

chiasmoptic

terminal nuclei

supericolliculi

NOT

LGN m

p

PARIETAL LOBE

FRONTAL LOBE

misphe

re right hemisphere

TEMPORAL LOBE

V1

V2

V3

V4

MT

hemifield left right

hemifield

Retina and LGN

ON OFF ONbipolars

ON OFF

ganglion cells

H

amacrine

AIIamacrine

AII

ON OFF bipolars

pigment epitheliumpigment epithelium

receptors

incoming light

photo-

conesrods

to CNS

cone horizontal

IPL

OPL

rods

to CN

receptors

ON

ON OFF

ganglion cells

H

S

cone horizontal

incoming light

photo-

cones

Visual cortex

Transforms in V1

Orientation

Direction

Spatial Frequency

Binocularity ON/OFF Convergence

Midget/Parasol Convergence

Original Hubel-Wiesel "Ice-Cube" Model

Left Eye Right Eye

Left Eye Right Eye

Swirl Model

Sub-cortical

Cortical

Radical Model

MidgetParasol

Three models of columnar organisation in V1

1 m

m

Figure by MIT OCW.

Striate Cortex Output Cell

Intracortical

Midget ON Midget ON

LEFT EYE Midget OFF Midget OFF RIGHT EYE INPUT INPUT

Parasol ON Parasol ON Parasol OFF Parasol OFF

luminance color

orientation spatial frequency

depth motion

The ON and OFF Channels

The receptive fields of three major classes of retinal ganglion cells

OFF

inhibition

ON

inhibition

ON/OFF

inhibition

Action potentials discharged by an ON and an OFF retinal ganglion cell

Stimulation confined to receptive field center

ON cell

OFF cell

Stimulation of the entire receptive field

ON cell

OFF cell

light spot dark spot

light stimulation condition

time

The midget and parasol channels

MIDGET SYSTEM PARASOL SYSTEM

ON OFFON OFF

neuronal response profile

time

P

Midget

1V

MT

Midget

Mixed

Parasol

w

?

Parasol

LGNM

PARIETAL LOBE TEMPORAL LOBE

2

V4

V2V

Projections of the midget and parasol systems

H

H

H

H

L

L

L

L

Proc

essi

ng C

apac

ity

Spatial Frequency

Temporal Frequency

Parasol SystemMidget System

Figure by MIT OCW.

Color vision and adaptation

Basic facts and rules of color vision

1. There are three qualities of color: hue, brightness, saturation

2. There is a clear distinction between the physical and psychological attributes of color: wavelength vs. color, luminance vs. brightness.

3. Peak sensitivity of human photoreceptors (in nanometers): S = 420, M = 530, L = 560, Rods = 500

4. Grassman's laws: 1. Every color has a complimentary which when mixed propery yields gray. 2. Mixture of non-complimentary colors yields intermediates.

5. Abney's law: The luminance of a mixture of differently colored lights is equal to the sum of the luminances of the components.

6. Metamers: stimuli producing different distributions of light energy that yield the same color sensations.

Basic facts about light adaptation

1. Range of illumination is 10 log units. But reflected light yields only a 20 fold change (expressed as percent contrast).

2. The amount of light the pupil admits into the eye varies over a range of 16 to 1. Therefore the pupil makes only a limited contribution to adaptation.

3. Most of light adaptation takes place in the photoreceptors.

4. Any increase in the rate at which quanta are delivered to the eye results in a proportional decrease in the number of pigment molecules available to absorb those quanta .

5. Retinal ganglion cells are sensitive to local contrast differences, not absolute levels of illumination.

The color circle

whitewhite

Yellow

Green

Red

hueBlue

saturation

black

Response to Different Wavelength Compositions in LGN Blue ON cell Yellow ON cell

90 90

30 40 0

45135

225 315

270

50 40 60 80

45135

180

225 315

270

Spikes per Second

20 1006010 20

20 0

10

45

90

135

225 315

90

135

20 30 40

45

180

225 315 maintained discharge rate

10

Green OFF cell Red ON cell

5030 40

0180

0180

270 270

Depth perception

Cues used for coding depth in the brain

Oculomotor cues Visual cues

accommodation Binocular vergence

stereopsis

Monocular motion parallax

shading interposition

size perspective

stereo camera

MOTION PARALLAX, the eye tracks

object motion

1

2

a

b

1

2

a

b eye movement

The eye tracks the circle, which therefore remains stationary on the fovea

Objects nearer than the one tracked move at greater velocities on the retinal surface than objects further; the further objects actually move in the opposite direction on the retina.

Form perception

Three general theories of form perception:

1. Form perception is accomplished by neurons that respond selectively to line segmens of different orientations..

2. Form perception is accomplished by spatial mapping of

the visual scene onto visual cortex.

3. Form perception is accomplished by virtue of Fourier analysis.

Eye-movement control

superior colliculus

sts ls

ce

p SC

visual cortex

FEF

MEF

frontal eye fields

medial eye fields

parietal cortex

V1

V2 LIP

BS

medial eye fields

ls ce

p FEF

MEF

frontal eye fields

BS

Anterior system

Posterior system

visual cortex

parietal cortex

V1

V2 LIP

SC

superior colliculusablated

sts

Summary of the effects of electrical stimulation:

V1 & V2, upper

V1 & V2, lower

V4

LIP

FEF

MEF

FACILITATION INTERFERENCE NO EFFECT FIX INCREASE

Summary of the effects of the GABA agonist

muscimol and the GABA antagonist bicuculline

Target selection Visual discrimination

muscimol bicuculline muscimol bicuculline

V1 V1

FEFFEF

LIPLIP

INTERFERENCE INTERFERENCE

INTERFERENCE FACILITATION

NO EFFECT NO EFFECT

DEFICIT DEFICIT

MILD DEFICIT NO EFFECT

NO EFFECT NO EFFECT

SC FACILITATION INTERFERENCE Hikosaka and Wurtz

Saccade to new location

A

what?

B

C

A

1 1. What are the objects in the scene?

2

A

B

Cwhich?

2. Which object to look at?

A

B

C

5

when?

5. When to initiate the saccade? 4. Where are the objects in space?

where?

A

B

C

4

3. Which object not to look at?

which not?

3

A

B

C

Brain areas involved

V1, V2, V4, IT, LIP, etc.

V1, V2, LIP, FEF, MEF

LIP

V1, V2, FEF, SC

V1, V2, LIP

BS

ras

?

BS

rate code

SC

SN

BG

vector code

P

Midget

1V

w

w

Parasol

LGN M

PARIETAL LOBE TEMPORAL LOBE

2

V4

V2

Midget

?

??

Mixed

Posterior system

Pa ol

MT

FRONTAL LOBE FEF MEF

vector code

place code Anterior system

V Auditory

system

Somatosensory

system

Olfactory

system

Smooth pursuitsystem

Vergence Accessory Vestibularsystem optic system system

Motion perception

Summary of cell types in V1

CXDL

L

LL

L

L

L

L

L

L

L

D

D

D

D

D

D

D

D

D

.1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 1.1 1.2 deg

.1 .2 .3 .4 .5

.1 .2 .3 .4 .5 .6 .7 .8

.1 .2 .3 .4 .5 .6 .7 .8 .9

.4.1 .2 .3 .5 .6

.1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 deg

.1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 deg

deg

deg

1.1

.1 .2 .3 .4 .5 .6 .7 deg

L

D

D

s6

s7

s5s1

s2

s3

s4

DEGREES OF VISUAL ANGLE

DEGREES OF VISUAL ANGLE

Figure by MIT OCW.

BS

Major Pathways of the Accessory Optic System (AOS) Velocity response of AOS neurons = 0.1-1.0 deg/sec Number of AOS RGCs in rabbit = 7K out of 350K

BS

rate code

D

M

L

Terminal Nuclei

Inferior Olive

Cerebellum

climbing fibers

Ant

NOT

Vestibular Nucleus

Semicircular canals

12

3

1

2,3

2,3

Cortex

Prime axes of retinal direction-selective neurons

vestibulo-ocular reflex

Effects of lesions on vision

severe

Summary of lesion deficit magnitudes

VISUAL CAPACITY PLGN MLGN V 4 MT color vision

coarse scotopic vision

brightness perception

contrast sensitivity

motion perception

flicker perception

fine

coarse

stereopsis fine

coarse

pattern perception

shape perception

texture perception

fine coarse

severe

severe

severe

severe

severe

severe

severe

mild

mild

mild

mild

mild

mild

mild

mild

none

none

none none none

none none

none none none

none none

none none

none none

none none

none none

none none none

none none none

none

none

none

none

none

none

moderate moderate

pronounced

mild

pronounced

fine

choice of "lesser" stimuli

not testedvisual learning

not tested

not tested

not tested

none none

none

not tested

severe

severe

severe

pronounced object transformation

INTE

RM

EDIA

TE

BA

SIC

VIS

UA

L FU

NC

TIO

NS

Prosthetics

Figure by MIT OCW.

The size and location of the regions activated in the monkey V1 by the dotted circle presented in the visual field 90 90

3

2

1

4

5

3

2

1

4

5

1 2 3 4

1 234

0

45

315

270

90 90

180

225

135

270

270

0180

135 45

315225

1 2 3 4

1 234

0

45

315

270

90 90

180

225

135

270

270

0180

135 45

315225

The size and location of the regions activated in the monkey V1 by the dots presented in the visual field

590 256 points 55

90

135 4 45 135 4 45

3 3

2 2

1 1

180 0 180 0

225 315 225 315

270 270

2 3 4 270 270 4 3 2 2 3 4 270 270 4 3 2 1 1 1 1

315 225 315 225

0 180 0 180

45 135 45 135

90 90 90 90

Illusions

The Hermann grid illusion

The most widely cited theory purported to explain the illusion:

ON ON

larger response smaller response

Due to antagonistic center/surround organization, the activity of ON-center retinal ganglion cells whose receptive fields fall into the intersections of the grid produces a smaller response than those neurons whose receptive fields fall elsewhere.

Differently oriented vertical and horizontal lines reduce illusion

Retinal ganglion cell receptive field layout at an eccentricity of 5 degrees

At the eccentricity of 5 degrees the 0.5 by 0.5 degree visual angle area outlined impinges on 365 midget cells and 50 parasol cells. Half of these are ON and half OFF cells. The layout of the ON cells is shown in B and C.

5mm 5 deg of visual angle

Retinal midget cells Retinal parasol cells

0.5 deg of visual angle