(week 3) Perception- visual system

Question 1

what is the stimulus for vision

Answer 1

light

Question 2

how is light characterised

Answer 2

by wavelength and intensity

Question 3

what does intensity of light mean

Answer 3

no. of photons per second

Question 4

what is the optic array

Answer 4

spatial distribution of light

Question 5

whats the function of the visual system

Answer 5

converts structured pattern of light into a perception of a solid 3D world

Question 6

what is the key problem with visual encoding

Answer 6

how is info encoded at diff. levels

Question 7

what are the 3 encoding principles

Answer 7

p of least commitment (dont throw away info you might need later)
p of least redundancy (encoding info efficiently as possible)
p of graceful degradation (if system breaks, it should still be useable)

Question 8

what is the order of activation in the retina

Answer 8

rods and cones -> bipolar cells -> ganglion cells

Question 9

what is the receptive field of the retina

Answer 9

region which when stimulated influences firing rate of the neuron

Question 10

what is phototransduction

Answer 10

photoreceptors (rods&cones) turn light into electricity

Question 11

what is visual electrophysiology

Answer 11

measures eye and brains electrical signals by placing tiny electrode close to visual neuron

Question 12

what are ganglion cells

Answer 12

convey info from the eye to the brain via the optic nerve
responds to contrast between centre and surround and finds intensity edges (interesting v boring)

Question 13

what is the LGN

Answer 13

lateral geniculate nucleus
in the brain
where info from both eyes starts to mix
6 layers

Question 14

what is retinopic organisation

Answer 14

ensures spatial layout of retina is preserved as info is passed to brain

Question 15

what are the 3 pathways in the LGN

Answer 15

M pathway- fast temporal changes
P pathway- fine detail, red-green colour
K pathway- blue- yelloe colour

Question 16

what is the striate cortex

Answer 16

a 6 layer highly complex initial cortical processing hub for visual info in the occipital lobe

Question 17

what are end stopped cells/ hypercomplex cells in the striate cortex

Answer 17

specialised cells in visual cortex that respond to moving corners and angles
length tuned

Question 18

what are complex cells of striate cortex

Answer 18

direction and orientation selective
collect info about motion

Question 19

what are simple cells in the striate cortex selective to

Answer 19

selective to orientation of light

Question 20

what is orientation tuning

Answer 20

the process where neurons fire selectively to specific edge angles or bar orientations

Question 21

what is the disparity energy model

Answer 21

explains how V1 complex cells in the visual cortex compute binocular disparity to perceive depth

Question 22

what is binocular disparity

Answer 22

differenece in receptive field position between the eyes-helps depth perception

Question 23

what is encoded in V2 of extra striate cortex

Answer 23

colour, form, depth

Question 24

what is encoded in V3 of extra striate cortex

Answer 24

motion, form

Question 25

what is encoded in V4 of extra striate cortex

Answer 25

colour, shape

Question 26

what is encoded in V5/ MT of extra straiet cortex

Answer 26

motion, depth