Eye movement 1

Question 1

4 types of eye movements

Answer 1

1) smooth pursuit
2) saccades
3) reflexes
4) vergence

Question 2

4 types of eye movements
describe smooth pursuit

how to test

Answer 2

tracking to keep an object on the fovea

keep head still and use object to track

Question 3

4 types of eye movements
saccades

how to test

Answer 3

rapid ballistic eye movement to bring object on to fovea = jumps

suppress visual info so don’t see blur of visual world

hold two fingers to smooth pursuit from finger to finger

Question 4

4 types of eye movements

reflexes

Answer 4

combo of pursuit + saccades

vestibuloocular reflex
optokinetic nystagmus

both involve nystagmus

Question 5

4 types of eye movements

vergence

Answer 5

moving fovea to object closer (convergence) or farther (divergence)

move object closer to you, eyes move medial

Question 6

Difference btwn conjugate and vergence eye movements

Answer 6

conjugate = both eyes move in same direction by sensory, visual and vestib inputs

vergence = eyes move in opposite direction (both eyes nasally during near reflex

Question 7

describe near rreflex

Answer 7

both medial recti contract pulling eyes nasally
pupils constrict to incr depth of field
ciliary contract so lens fatter to focus on near object

Question 8

describe saccade

Answer 8

rapid movement that brings eyes to predetermined target or position up to 700 degrees/sec

Question 9

uses of saccades

Answer 9

1) resotre eye toward center of orbit when visually or vestib evoked
2) or rapidly foveate an interesting periph stim moving away from center of orbit

Question 10

what does it mean to say visually evoked saccades are ballistic

process?

Answer 10

programmed to foveate a particular target even if target moves after saccade initiated

1) high freq burst for initial accel
2) steady rate to maintain eye position

if head also rotate, saccade has to include later modif

info during saccade suppressed

Question 11

describe optokinetic nystagmus

Answer 11

rhythmic saccades and tracking movements caused by simple stim (rotating striped drum)

Question 12

control of saccades

in brain

Answer 12

frontal eye field –> via corticopontine fibers –> PPRF

frontal eye field –> superior colliculus –> PPRF

Question 13

where is pattern generator for vertical saccades?

where is pattern generator for horizontal saccades?

Answer 13

near oculomotor nuclei (midbrain)

PPRF (near abducens nucleus)

Question 14

horizonal saccades are driven__ (ipsil or contralat)

Answer 14

contralaterally

saccade to left driven by activity in right frontal eye field

Question 15

2 important control centers for saccades___

Answer 15

1) cortex
2) superior colliculsu

voluntary movements of pattern generators driven by frontal lobe
either direct to PPRF or via superior colliculus to PPRF

Question 16

activation via superior colliculus involves what kinds of layered maps

Answer 16

1) retinotopic map
2) auditory spatial map
3) somatotopic map

Question 17

describe smooth eye pursuit

can only maintain foveation at what rate? meaning?

Answer 17

elicited by large moving stimulus to feveate that stimulus for more extended visual examination

maintain foveation at 50 degrees/sec or less because coord smooth pursuit involves lots of analysis in visual cortex (position, direction, speed)

if faster than 50 degrees/sec, saccades + smooth pursuit

Question 18

what brain part controls saccades?

what if damage area 8, SC, both?

Answer 18

area 8 in prefrontal cortex

if damaged = still make saccades but not as graceful

if damage superior colliculus can still make

if damage both = no saccades