visual thalamus and cortex- lecture 10

Does each optic tract responds to contralateral or ipsilateral halves of the visual field?

contralateral half of the visual field

Where does the joining of the optic nerves take place?

the optic chiasm

True or false: same half of the visual field projects onto temporal hemiretina in one eye, and nasal hemiretina in the other eye

true

Axons of ganglion cells in the nasal half of the retina cross at the optic chiasm to where?

the opposite optic tract

How many layers are there if the LGN?

6

How is the LGN structured?

individual LGN cells receive input from 1 eye (contralateral) and layers alternate input from each of the 2 eyes

What cells of the LGN are contralateral?

1, 4, and 6

What cells of the LGN are ipsilateral?

2, 3, and 5

What makes up the LGN topographic map?

-map of the visual hemifield in each layer

-maps for each layer are in register

What is the LGN?

lateral geniculate nucleus

What layers of the LGN are P-type cells most abundant, also called the parvocellular layer?

LGN layers 3-6

What layers of the LGN are M-type cells most abundant, also called the magnocellular layer?

LGN layers 1-2

What layers of the LGN are small bistratified cells most abundant, also called the konicellular layer?

in between the LGN layers

Red/green cells are located in what layers?

parvocellular layers

Blue/yellow cells are located in what layer?

koniocellular layers

Black/white cells are located in what layer?

magnocellular layers

Parvocellular cells process what?

form and color info

Koniocellular cells process what?

color info and possibly more

Magnocellular cells process what?

motion and depth infro

True or false: different layers of the LGN have the same functions

false

The magnocellular pathway projects to what V1 layers?

sublayer 4Ca (alpha)

The parvocellular pathway projects to what V1 layers?

sublayer 4Cb (beta)

The koniocellular pathway projects to what V1 layers?

1-3

Left V1 represents what half of the visual field?

right half of the visual field

What are ocular dominance columns?

alternating columns that receive information from only 1 eye

What layer of the V1 has alternating inputs?

4C in V1

Information from each eye is combined in what layer of V1?

layer 3

What is monocular input?

cells that receive input from either the left or the right eye

What s binocular input?

cells receive input from both eyes and contribute to 3D and depth processing

V1 cells respond best to and allows for what?

specific orientation of the stimulus allowing for detection of orientation

Does orientation selectivity of cells stay the same or change as you move perpendicular to the surface and why?

stays the same as the probe would remain in the same minicolumn

Does orientation selectivity of cells stay the same or change as you move parallel/ laterally to the surface and why?

changes as the probe would move through different minicolumns

Why are many V1 cells direction selective?

they prefer movement in 1 particular direction which helps with motion detection and project to area MT

Do simple cell receptive fields have distinct on and off regions?

yes, to help determine orientation preference

Converging LGN input results in what?

simple cell RF with elongated on regions

Why do complex cells have no distinct on and off regions?

simple cells project to create complex cells and each simple cell has a different on/off preference causing them to cancel out and only have orientation preference

What are blobs?

an enzyme called cytochrome oxidase found in the mitochondria that contribute to cellular respiration, is differentially distributed across V1

What layers are blobs found in and in what intervals?

blobs extend through layers 2/3 and 5/6 at regular intervals in V1

What are blobs thought to contribute to?

color processing

A module of V1 does what?

it is capable of analyzing every aspect of a single part of visual space

What do V2 cells respond to?

angles or the component lines that form preferred angles

What do V4 cells respond to?

sensitive to form and color (ie colored shapes)

What do MT/V5 cells respond best to?

respond best to stimuli moving in particular directions (motion directions and velocities)