lecture 3

Question 1

what is the function of the ganglion cells?

Answer 1

to condense raw information from the photoreceptors, aim to extract important information from the retinal image

Question 2

ratio of retinal ganglion cells to photoreceptors?

Answer 2

1: 126

Question 3

basis of single cell recording

Answer 3

physiological approach
an electrode is inserted into a neuron that measures electrical activity
activity is of that single neuron
an increased rate of action potentials indicates an increased activity of the neuron

Question 4

what is an experimenter trying to find from single cell recording?

Answer 4

a stimulus that changes the activity of the cell from baseline

Question 5

receptive field

Answer 5

area on the retina which, when stimulate by light, elicits a change in the firing rate of the cell

Question 6

how are ganglion cells influence by a whole region on the retina?

Answer 6

convergence

horizontal and amacrine cells

Question 7

excitatory region causes

Answer 7

an increase in the cell’s response rate

Question 8

inhibitory region causes

Answer 8

a decrease in the cells response rate

Question 9

features of the receptive fields of the visual field?

Answer 9

each photoreceptor is part of the receptive field of more than one ganglion cell
receptive fields of neighbouring ganglion cells overlap
receptive fields of all ganglion cells together cover the whole visual field

Question 10

what is lateral inhibition?

Answer 10

inhibition transmitted across the retina by horizontal and amacrine cells

Question 11

what is the organisation of receptive fields on the retina?

Answer 11

centre surround antagonism

Question 12

what are the two forms of centre surround antagonism?

Answer 12

ON centre OFF surround

OFF centre ON surround

Question 13

what do ganglion cells respond to?

Answer 13

detects spots of lights and edges (contrast)

respond to changes in pattern of light as this carries the most important information

Question 14

what do ganglion cells not respond to/ detect

Answer 14

not able to detect the orientation of bars

no response to changes in overall level of illumination

Question 15

how do ganglion cells reduce the amount of information in a stimulus

Answer 15

by finding boundaries and contours. In all dark or all illuminated areas there will be baseline firing of cells. Where there is a boundary an excitatory or inhibitory effect will be exhibited

Question 16

where are receptive fields smallest?

Answer 16

at the fovea

Question 17

why do we see a darker stop at the intersection of the hermann grid?

Answer 17

more light falls onto the off region so receives more inhibition and cells fire less
less firing is interpreted as less bright so we perceive a darker spot