spatial vision

Question 1

do the 6 different layers in V1 contain different types of neurons?

Answer 1

YES

Question 2

some layers in V1 are ___ layers and some are ___?

Answer 2

input and output

Question 3

neighbour relationships in retina are retained in the … ?

Answer 3

cortical map

Question 4

all neurons stacked on top of each other in V1 respond to the ___ - but react to ___ ?

Answer 4

• same orientation
• different sizes

Question 5

neurons change orientations by ___ as you move through V1?

Answer 5

10 degrees

Question 6

do binocular neurons have a preference for right or left eye?

Answer 6

YES even though they receive from both

Question 7

what are ocular dominance bands?

Answer 7

eyes that respond to left organised together and vice versa for right

Question 8

what is a hyper column in the V1?

Answer 8

• collection of neurons that all have receptive fields that cover the dame parts of visual space - within that, they respond to different orientations

Question 9

neurons within one orientation column (stacked on top of each other) might respond to different sizes e.g., fatter or thinner bars of light?

Answer 9

TRUE

Question 10

what can be changed about sinewaves?

Answer 10

• change orientation (can study orientation tuning)
• change spatial frequency (size of stimuli)
• change contrast
• change phase - where does the cycle start e.g., at black or white?
• luminance changes as you move from left to right of the sinewave (the amount of light)

Question 11

what are sinewaves?

Answer 11

• dark and light bars
• no hard edge between the bars

Question 12

how can we specify spaial frequency?

Answer 12

seeing how many cycles fit into one degree

Question 13

what does the visual angle tell us?

Answer 13

• the visual angle tells us the size of the retinal image (given a certain object size at a certain distance)
• doesn’t matter the size of object in the environment as we don’t have access to that, we only have access to what is projected onto our retina at the back of eye (retinal image)

Question 14

what is the Fourier analysis?

Answer 14

• every image can be broken down into sinewave components – Fourier analysis
• the visual system conducts the equivalent of a local Fourier analysis
• can use FA to deconstruct images and make them into sinewaves

Question 15

hyper columns and Fourier analysis?

Answer 15

• hyper columns contain neurons tuned to different orientations and spatial frequencies
• all of these neurons analyse the same patch of visual space
• together, they extract spatial frequency components and orientation components contained in ‘their’ local patch – they conduct a local Fourier analysis

Question 16

what is adaptation happen - method and process?

Answer 16

• both a method and a process in the visual system
• method: Stare at the same stimulus for a long time
• process: As a consequence of long exposure, those neurons that are tuned to the stimulus property decrease their sensitivity
• example: Tilt Aftereffect

Question 17

how can population codes tell you a specific image has a grating of vertical lines?

Answer 17

• have population neurons
• within, neurons arranged in columns
• look at grating
• in the centre, one neurons tuned to vertical orientations - would respond at optimal rate to this grating
• if tuned slightly to the right - would not respond at optimal response
• all these neurons contribute to activation profile
• that specific profile tells your brain the image is the grating of vertical lines

Question 18

what is contrast sensitivity function?

Answer 18

• sensitivity of our visual system differs for different spatial scales
• contrast sensitivity function (CSF) = How sensitive are we to inputs
• 3-10 degrees - most sensitive to visual inputs

Question 19

what produces the contrast sensitivity function?

Answer 19

• represented by neurons who are sensitive to fat bars
• population of neurons tuned to similar spatial frequency forms a spatial frequency channel