Lecture 13lecture 13 complete up to class)

5 kinds of neurons in the retina

photoreceptors, bipolar cells, ganglion cells, horizontal cells, and amacrine cells

Rods

Work for dim light; constantly releases glutemate

cones

work for bright light and to see colors; constantly releases glutamate unless experiencing light

Melanopsin

Photopigment responsible for sleep regulation and non visual light responses

off Bipolar cells

Excited by glutamate; In the dark they are active and in the light quiet

Bipolar cells

Works to transmit signals from photoreceptors to ganglion cells

On bipolar cells

Glutamate inhibits them, causing them to be excited nby light

Horizontal cells

send inhibitory signals around it (photoreceptors and bipolar cells)

Amacrine cells

Work in the inner synaptic layer; mostly inhibitory, and have no axon; multiple different types have a variety of output functions

ganglion cells

They fire action potentials toward the optic nerve that sends it to the occipital lobe

Midget cells

have tiny fields: fine details and color

parasol cells

have wide fields for motion and contrast

Iris

muscle that controls how much light enters the pupil

Pupil

An opening rather than a structure in the eye

Lens

focuses

Inside the retina process

Light passes through the transparent ganglion and bipolar cells to reach the photoreceptors in the back, where the optic nerve will than link the signal in order to process the stimuli

retinal disparity

slight difference between the images projected onto each eye due to horizontal separation

Blind spot

where there are no receptors

what is the visual pathway to the brain

Ganglion cell axons leave each eye as the optic nerve, at stopps at the lateral geniculate nucleus of the thalamus and than to the visual cortex

Trichromatic theory

three colors of light can be mixed to make any color

Opponent processing theory

Proposes that there are two opposing color sets, red-green and blue-yellow, that make up every color

Negative color affect effect

demonstrates opponent processing theory, if you stare at red, then look at white, you’ll see green

Explaination for black and white colors

Mixing lights adds wavelength to create white while mixing paints absorbs wavelengths to create black

What is the combined theory

Three cone types are wired oppositely to ganglion cells in order to excite or inhibit certain perceptions of color

Color vision deficiency

One or more cone types respond poorly or not at all

Red-green CVD

both colors are seen but can’t be told apart

Tritanopia

blue and yellow are seen but cannot be told apart, very rare

Form vision

finding an objects edge

Lateral inhibition

Each neuron inhibits its neighbor, which causes brightness contrast at edges