l 23 retinal circuitry

Question 1

spatial frequency tuning

Answer 1

visual system is tuned to a particular spatial frequency

- max sensitivity if dark adapated, shifts to the right if light adapted

Question 2

sine wave stimuli of different spatial frequencies

Answer 2

wavelength over space (cycles/degrees)
low SF: long eavelength
high SF: short wavelength

Question 3

since wave stimuli of different contrast

Answer 3

sensory stimuli geared towards contrast

- amplitude contrast of response

Question 4

spatial frequencies in surround

Answer 4

surrounds = low spatial frequencies
center = high spatial frequencies
- optimal size where bar fills up receptor but not surround

Question 5

what do the mechanisms that shut off bipolar cells depend on

Answer 5

block GABA and see no response
block TTX and conclude GABA comes from amacrine cells
voltage clamp to measure glutamate -60, measure inhibitory GABA by holding at 0mV

Question 6

horizontal cells mediate surround inhibition

Answer 6

in dark: photoreceptors depolarize, horizontal are also depolarized so they provide tonic inhibition
when shine light, hyper photoreceptors to stop releasing glutamate and hyperpolarize horizontal to stop releasing GABA

Question 7

ribbon synapses

Answer 7

photoreceptors have specialized ribbon synapses that support tonic release of vesicles
- mediated by L type calcium channels but only activate at Vm > -40

Question 8

activation of Ca channels and dynamic range of photoreceptors

Answer 8

photoreceptors rest at -40mV and hyperpolarize with light

unsure how to use Ca channels because range is mismatched

Question 9

Appaloosa horses

Answer 9

mutations in rod L type calcium channels leads to congenital stationary night blindness in appaloosa horses
- linked to coat color, spot was genetically linked to ca channel adn animals without spots were more blind

Question 10

synaptic organization in outer plexiform layer

Answer 10

1. ribbon synapses

2. provide input to several cell types

Question 11

bipolar cell types and responses

Answer 11

photoreceptor hyperpolarizes, stops releasing glutamate
off: works same as neuron, hyperpolarizes glutamate activates AMPA
on has to depolarize and inverts response, glutamate is coupled to inhibitory GPCR which closes channels

Question 12

on and off circuits

Answer 12

anatomically segregated in different layers of IPL

Question 13

bipolar cell to ganglion cell

Answer 13

bipolar varies intensity of light in graded fashion

ganglion is fixed number of action potentials, conversion from anallog to digital

Question 14

rod bipolar cells

Answer 14

do not contact ganglion cells, pass signals through all amacrine cells

Question 15

amacrine cell to cone bipolar cells

Answer 15

amacrine cell depolarizes
OFF bipolar cell sign inverting glycinergic pathway
ON bipolar cell through sign preserving electrical coupling pathway

Question 16

rod circuitry

Answer 16

rods connect to 1 bipolar cell called rod bipolar cell (cones connect to other 14) all signals go to 1 so how does information get distributed to 30 types of ganglion
a2 amacrine cells are activated and make gap junction connections to bipolar cells
activating rods activates A2 which activates other bipolar