Lecture 11

Question 1

what are the 2 systems needed for clear and stable vision?

Answer 1

eye movement system (stabilize image on fovea) and accommodative system (clear image)

Question 2

what is a saccadic eye movement?

Answer 2

brings the image of an object of interest rapidly onto the fovea

Question 3

what is a smooth pursuit eye movement?

Answer 3

holds the image of a small moving target on the fovea

Question 4

what is a vergence eye movement?

Answer 4

moves the eyes in an opposite direction so that images of a single object are held simultaneously on both fovea

Question 5

what are 3 eye movements that direct the fovea to an object of interest?

Answer 5

saccades, smooth pursuits and vergences

Question 6

what are 3 eye movements that hold images steady on the retina?

Answer 6

fixation, vestibular (VOR) and optokinetic

Question 7

what is a fixation eye movement?

Answer 7

holds the image of a stationary object on the fovea when head is immobile

Question 8

what is a vestibular (VOR) eye movement?

Answer 8

holds the image steady on the retina during brief head movements

Question 9

what is an optokinetic eye movement?

Answer 9

holds image steady on the retina during sustained head movements or when the environment moves around the head

Question 10

what are monocular eye movements called?

Answer 10

ductions

Question 11

what are versions?

Answer 11

conjugate eye movements - 2 eyes move in the same direction by the same amount

Question 12

what are vergences?

Answer 12

disjugate eye movements - 2 eyes move in opposite directions

Question 13

what are the movements called for ductions in the z, y, and x-axis?

Answer 13

z = abduction and adduction
y = elevation (supraduction) and depression (infraduction)
x = incyclotorsion and excyclotorsion

Question 14

what are the movements called for versions in the z, y and x-axis?

Answer 14

z = dextroversion and levoversion
y = elevation and depression
x = dextrocycloversion and levocycloversion

Question 15

what are 4 types of version movements (conjugate)?

Answer 15

saccadic movement, smooth pursuit, vestibular (VOR) movement and optokinetic movement

Question 16

what do conjugate eye movements control?

Answer 16

gaze control

Question 17

what do disjugate eye movements control?

Answer 17

vergence control

Question 18

what is the input to the frontal eye fields (FEF)? what is the output?

Answer 18

input = many cortical and subcortical areas 
output = superior colliculus and other gaze centers

Question 19

what is the function of the frontal eye fields (FEF)?

Answer 19

voluntary eye movements (not guided by target) and scanning the visual field

Question 20

where are the frontal eye fields located?

Answer 20

frontal lobe of cerebral cortex (brodmann’s area 8)

Question 21

where is the superior colliculus (SC) located?

Answer 21

pair of nuclei located on the upper surface of the midbrain

Question 22

what is the input to the superior colliculus (SC)?

Answer 22

retina, auditory system, somatosensory system and frontal eye fields

Question 23

what is the output from the superior colliculus (SC)?

Answer 23

to other gaze control centers

Question 24

what is the function of the superior colliculus (SC)?

Answer 24

controls the direction and magnitude of saccades

Question 25

where is the horizontal gaze center (PPRF) located?

Answer 25

located in the reticular formation of the pons (known as the Paramedian Pontine Reticular Formation)

Question 26

what is the input to the PPRF?

Answer 26

directly from the superior colliculus, FEF or cerebellum

Question 27

what is the output from the PPRF?

Answer 27

to nuclei of motor nerves controlling horizontal eye movements (directly or crossing midline via MLF)

Question 28

where is the vertical gaze center NIC located?

Answer 28

in the rostral part of the midbrain reticular formation (Interstitial Nucleus of Cajal)

Question 29

what is the output from the NIC?

Answer 29

to nuclei of motor nerves controlling vertical eye movements (CN3 and CN4)

Question 30

what is the medial longitudinal fasciculus (MLF)?

Answer 30

a midline tract in the medial midbrain and pons - connects the nuclei of the 3 eye movement motor nuclei

Question 31

what is the input or stimulus for a saccade?

Answer 31

target position, angle in degrees

Question 32

what is the input or stimulus for a pursuit?

Answer 32

target motion deg/sec

Question 33

what is the input or stimulus for a vergence?

Answer 33

vergence stimulation from disparity

Question 34

what is the input or stimulus for accommodation?

Answer 34

target distance in diopters

Question 35

what is the input or stimulus for VOR/OKN?

Answer 35

target velocity and head velocity

Question 36

what is the output in accommodation?

Answer 36

change in focus

Question 37

what is the output in a saccade?

Answer 37

change in angle of the eye/position

Question 38

what is the output in a pursuit?

Answer 38

change in velocity of the eye

Question 39

what is the output in a vergence?

Answer 39

change in position of the eyes

Question 40

what is the output in VOR/OKN?

Answer 40

change in velocity of the eyes

Question 41

how does an open loop system work?

Answer 41

none of the output is fed back into the input (no fine-tuning of the response)

Question 42

how does a closed loop system work?

Answer 42

all or part of the output is fed back into the input altering the final output