M2 Lecture 11: Feb 19

Question 1

what is Accommodation

Answer 1

The process by which the eye changes its focus (in which the lens gets fatter as gaze is directed toward nearer objects) – useful < 2-3 meters

Question 2

what is Convergence

Answer 2

The ability of the two eyes to turn inward, often used to focus on nearer objects.

Question 3

what is Divergence:

Answer 3

The ability of the two eyes to turn outward, often used to focus on farther objects.

Question 4

what are the binocular cues

Answer 4

accommodation, convergence and divergence

Question 5

what is Binocular summation:

Answer 5

The combination (or “summation”) of signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone

Question 6

what is Binocular disparity:

Answer 6

The differences between the two retinal images of the same scene

Question 7

Disparity is the basis for what

Answer 7

stereopsis

Question 8

what is stereopsis

Answer 8

a vivid perception of the three-dimensionality of the world that is not available with monocular vision

Question 9

what is Corresponding retinal points:

Answer 9

A geometric concept stating that points on the retina of each eye where the monocular retinal images of a single object are formed are at the same distance from the fovea in each eye

Question 10

what is Vieth–Müller circle (Horopter):

Answer 10

The location of objects whose images lie on the corresponding points. The surface of zero disparity.

Question 11

Objects on the horopter are seen as what

Answer 11

single images when viewed with both eyes.

Question 12

Objects significantly closer to or farther away from the horopter fall where

Answer 12

on noncorresponding points

Question 13

Objects significantly closer to or farther away from the horopter fall on noncorresponding points in the two eyes and are seen as how many images

Answer 13

2

Question 14

what is Diplopia:

Answer 14

Double vision. If visible in both eyes, stimuli falling outside of Panum’s fusional area will appear diplopic.

Question 15

what is Panum’s fusional area:

Answer 15

The region of space, in front of and behind the horopter, within which binocular single vision is possible.

Question 16

what is Crossed disparity

Answer 16

The sign of disparity created by objects in front of the plane of the horopter

Question 17

Images in front of the horopter are displaced how

Answer 17

to the left in the right eye and to the right in the left eye.

Question 18

what is Uncrossed disparity:

Answer 18

The sign of disparity created by objects behind the plane of the horopter.

Question 19

Images behind the horopter are displaced where

Answer 19

to the right in the right eye and to the left in the left eye.

Question 20

Different binocular neurons in V1 encode all categories of retinal disparity (zero, crossed (near), and uncrossed (far)).

These neurons are organised how

Answer 20

into columns

Question 21

Different binocular neurons in are V1 encode all categories of retinal disparity (zero, crossed (near), and uncrossed (far)).

These neurons allow perceiving what

Answer 21

depth within Panum’s fusional area.

Question 22

what is Stereoscope

Answer 22

A device for presenting one image to one eye and another image to the other eye.

Question 23

explain how 3D glasses work

Answer 23

For movies to appear 3D, each eye must receive a slightly different view of the scene (just like in real life).
Early methods for seeing movies in 3D involved “anaglyphic” glasses with a red lens on one eye and a blue lens on the other.
Current methods use polarized light and polarizing glasses to ensure that each eye sees a slightly different image.

Question 24

what is Correspondence problem

Answer 24

In binocular vision, the problem of figuring out which bit of the image in the left eye should be matched with which bit in the right eye

the question is Do we need to recognize objects to have stereopsis?

Question 25

what is Random dot stereogram (RDS):

Answer 25

A stereogram made of a large number of randomly placed dots.

Question 26

RDSs contain what cues to depth

Answer 26

no monocular

Question 27

Stimuli visible stereoscopically in RDSs are cyclopean stimuli, what is cyclopean

Answer 27

Referring to stimuli that are defined by binocular disparity alone.

Question 28

what is Free fusion:

Answer 28

The technique of converging (crossing) or diverging (uncrossing) the eyes in order to view a stereogram without a stereoscope

Question 29

(for RDS) If the “object” on the right eye is positionned to the left of the object on the left eye (if there is crossing), the object will be perceived where

Answer 29

in front of the background (and vice-versa).

Question 30

what is Binocular rivalry:

Answer 30

The competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes.

-> the retinal input is constant, but the percept changes!

Question 31

What tracks the percept

Answer 31

Patterns in V1-V3!

Question 32

V1 tracks more what than the percept

Answer 32

the eye

Question 33

Logically speaking, motion perception shouldn’t require anything else than what

Answer 33

the ability to perceive successive still frames.

Question 34

what is Akinetopsia

Answer 34

A rare neurophysiological disorder in which the affected individual has no perception of motion.

Question 35

Akinetopsia can be caused by what

Answer 35

can be caused by lesion of areas MT/MST

Question 36

e.g. of Akinetopsia (just an example to solidify the issue)

Answer 36

A 47-year-old man reported seeing streams of multiple, frozen images trailing in the wake of moving objects. As soon as motion ceased, the images collapsed into each other. he compared his vision to a scene lit by a flashing strobe, except that stationary elements were perceived normally. In fact, if nothing was in motion and he held perfectly still, his vision was entirely normal. The moment anything moved, however, it left a stream of static copies in its path. For example, while out for an evening stroll, he saw a pack of identical dogs lined up behind his West highland terrier. Driving was impossible because he was confused by multiple snapshots of cars, streets, and signs. Moving lights were followed by a long comet trail»

Question 37

what is Apparent motion

Answer 37

The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession.