16- Evolution

Question 1

Most animals with high levels of … have mobile eyes?

Answer 1

acuity

Question 2

Humans and other primates make a range of eye movements, including 1,2,3 pursuit.

Answer 2

1- fixational,
2- saccadic,
3- smooth

Question 3

Some species (e.g. mantis shrimp and jumping spider) use what to exploit particular aspects of their visual system?

Answer 3

slow eye movements

Question 4

Many animals sample the visual scene using which 2 types of strategy?

Answer 4

saccade and fixate

Question 4

Compensatory eye movements may enhance what?

Answer 4

motion sensitivity

Question 5

The oculomotor system has evolved mechanisms for keeping … stable in which type of environments?

Answer 5

gaze,
dynamic

Question 6

Physiology of eye movements:

How many extraocular muscles do humans have, and which type of pairs do they operate in?

Answer 6

6 extra ocular muscles
antagonistic pairs

to elevate eye: use Superior Rectus (top) Inferior Rectus (bottom)
to move eye left and right: Medial Rectus (horizontal plane) Lateral Rectus (ear) abduction and aduction
Oblique muscles work in concert with other muscles in other directions in gaze as they introduce torsonal movements of the eye

Oculomotor nucleus located in the Midbrain, has a specific pattern path to the Caudial Midbrain. (cranial nerves)
Lateral Rectus damage (abduct to midline restraint of eye movement)

Question 6

Name the 4 types of eye movements:

Answer 6

Fixational eye movements
Saccadic eye movements
Smooth pursuit eye movements
Vergence eye movements

Question 7

when fixation is stabilized, useful distance information can be extracted from which type of fields?

Answer 7

Retinal flow

Question 7

Which eye movement is this?

ballistic eye movement (up to 1000 deg/s) that moves fixation from one point in space to another
we make 3-4 saccades every second
saccades move our fixation around interesting parts of an image
but we suppress (reduce visual sensitivity) to eliminate motion blur

Answer 7

Saccadic eye movements

Saccadic surpoession

Question 8

Physiology of eye movements:
brain circuits and innervation of which type of muscles mediating eye movements?

Answer 8

extra-ocular muscles

Question 8

The reduction of perceptual fading (when you stare at an object, all other objects in the periphery start to disappear due to decaying firing in neurons) is also known as which effect?

Answer 8

Troxler effect

Question 9

Which eye movement is this?

control of fixation position,
reduction of perceptual fading (Troxler effect),
generation of synchronized transient visual activity,
enhancing visual acuity and scanning across visual space

Answer 9

Fixational eye movements

Question 10

Which eye movement is this?

Eyes follow an object moving through space to keep the object imaged on the fovea (i.e. there is no net retinal motion).
Trying to match motion of retina to objects in visual field
Found in humans and other primates
(you need a high forvea to engage in this eye movement)

Answer 10

Smooth pursuit eye movements

Question 10

Which eye movement is this?

The angle of the eyes are moved in opposite directions to put a near object of interest on the fovea of each eye
objective is to keep fovea aimed at object in both retinas
(kinda cross eyed)

Answer 10

Vergence eye movements

Question 11

Which eye movement is this?

Very high frequency and very low amplitude related to musculature of the eyes

Answer 11

Fixational eye movements
tremor

Question 11

Which eye movement is this?

Very small sequences of speedy and amplitude in eye movements eg. eyes will jump and drift, jump and drift

Answer 11

Fixational eye movements
microsaccades

Question 11

Which 2 eye movements are described as being relatively slow?

Answer 11

Vergence and Smooth Pursuit eye movements

Question 11

Name the 3 types of fixational eye movement:

Answer 11

ocular drift,
tremor,
microsaccades

Question 12

Which eye movement is this?

Quite slow, eyes drift about not necessarily in the same direction (Vergence eye movement compensates for this)

Answer 12

Fixational eye movements
ocular drift

Question 13

info slide

Answer 13

Direct projection of some retinal ganglion cells down to the superior purcolous (20%) the rest leaves the back of the eye at the optic nerve to the LGN. At this point the layers are kept separate (PVC layers) and project to V4 to V1 lateral intraparietalcortex project to midbrain and Superior callous

LIP is involved with attentional regulation and visual working memory

Question 13

A major challenge for the oculomotor system is to keep gaze stable while head/ body or eyes move.

Which 2 reflexive types of eye movements have evolved in humans to achieve this?

Answer 13

Vestibular Ocular Reflex
Opto-Kinetic Response

Question 13

Which illusion is known for making your eyes move in the opposite direction every time you look around the image despite trying to remain fixated?

Answer 13

Spine Drift Illusion

Question 13

Which reflexive types of eye movement has evolved to:

prevent involuntary rotation of the eyes relative to surroundings

initiated by rotation detectors in the semi-circular canals (in inner ear), which have cells that fire in proportion to head velocity

results in a movement of the eyes in equal and opposite direction to the head

VOR is fast, operates up to 10Hz OWLS?

Answer 13

Vestibular Ocular Reflex

Question 14

Which reflexive types of eye movement has evolved to: use signals from motion detectors to cancel out residual movement between image and retina if object moves rightwards across the retina, a rightwards eye movement will limit the amount of relative motion we ‘assume’ the world is stationary and we fix gaze relative to it causes induced nystagmus (sawtooth movements of the eyes) involves a large field stimulus and must be suppressed when pursuit eye movements track small foveal target OKR is slow - effective up to 1Hz?

Answer 14

Opto-Kinetic Response eyes lock onto a bar until it reaches out of orbid, eye will jump back to a different bar at the beginning ect (looking at sheep on the train) this stablises gaze relative to the rest of the visual field.

Question 14

What are the 3 consequences of image motion blur: resolution is ... when motion blurs an image easier to detect foreground motion when background is ... heading and distance information are ... to recover from pattern of retinal stimulation when translation is removed

Answer 14

degraded stationary easier

Question 14

Is the Vestibular Ocular Reflex fast?

Answer 14

Yes

Question 14

Is the Opto-Kinetic Response fast?

Answer 14

No, slow

Question 15

Primates use which 2 eye movement strategies?

Answer 15

saccade and fixate strategy gaze rotation in space = head + eye; dots = fixations; lines = saccades see both fast saccadic movements of the eye and slow movements opposite to head (VOR) gaze fixations are steady (traces displaced relative to one another for clarity)

Question 15

ocular drift, tremor, microsaccades are all part of which eye movement?

Answer 15

fixational eye movement

Question 15

Which animals other than primates use saccade and fixate strategy?

Answer 15

Goldfish and crabs, despite evolutionary differences, use saccade and fixate behaviour

Question 16

Which type of movement do flies have?

Answer 16

Insects do not have eye movements (move head), they have a head saccade rather than an eye saccade, to keep the fly steady during flight while it rotates its body movement which is continuous; head and eyes rotate in saccade-like movement Flight behaviour of Cerceris (head orientation) (small wasp) leaving nest have changes in body position, yet fixtation is kept stable to try and locate landmarks in relation to their nest

Question 16

True of False: Most animals with good vision use the same saccade and fixate strategy, though this can be in the form of eye, head or body movements?

Answer 16

True

Question 17

Name an example of behavioural translational saccades in birds:

Answer 17

Head -bobbing techniques -gives a period of very stable gaze while on the ground between those where vision is compromised by motion. if background motion is removed (treadmill) pigeons do not head-bob birds with frontal eyes (e.g. eagles, owls) do not head-bob smaller birds show similar behaviour by hopping (jump and hold phases)

Question 18

Consequences of motion blurring: info slide Not representing the contrast correctly in an image is known as motion blurring and has huge impact on high resolution visual systems

Answer 18

If you have a lower resolution system , you have higher tolerance to motion blurring but because humans experience motion blur at very low speeds, we must stablise vision in which we have evloved the Vestibular Ocular Reflex and Opto-Kinetic Responses.

Question 18

Stabilising vision in eyes helps to pick up motion in our visual fields

Answer 18

Compensatory eye movements may enhance sensitivity to motion parallax

Question 18

We can estimate distance using retinal flow fields (speed estimates, but when adding translation, it becomes very difficult to do. To overcome this, we stabilise our gaze.

Answer 18

Distance information can be obtained from the flow field if image is stabilised to remove rotations.

Question 19

What is it called when we fixtate our gaze onto an object but move our body towards or around the object?

Answer 19

Generating motion parallax movements lateral translation (without rotation) allows animals to estimate the distance of objects Exploiting this approach requires ability to precisely locate edges.

Question 19

Which animals generate motion parallax movements?

Answer 19

locusts and mantids (peering) bees (roll m/ments of thorax) gerbils (head bobbing)

Question 20

Exceptions to the rule: scanning eyes Holding your gaze is beneficial to many animals but some do not use this. Which 2 species actively rotate their eyes in order to acquire visual information?

Answer 20

(a) mantis shrimp - ambush predators that smash or spear prey - each eye makes independent movements (b) jumping spider - has pairs of secondary eyes and large - forward pointing principal eyes with secondary eyes used only for motion detection - movements designed to detect the orientation of linear structures - legs!