Sensorimotor Integration

Question 1

Why study eye movements

Answer 1

1. eye movements can be accurately measured
2. only 6 muscles control the position of each eye
3. neural circuits controlling eye movements do not need to compensate for variable loads over time

Question 2

Distinction between foveal and parafoveal vision

Answer 2

• eye movements important because high visual acuity is restricted to the fovea

Question 3

saccades

Answer 3

• quick, ballistic eye movements that occur several times per second during normal vision
• landing / fixation points of saccades
• lines that connect the dots to indicate the saccades trajectories
• helpful in giving high resolution visual info about hte target you’re about to interact with

Question 4

tiny eye movements for what purpose

Answer 4

• if the visual image is stabilised perfectly on the retina, then visual preception of the scene rapidly fades away
• thus tiny eye movements prevent this retinal adaptation

Question 5

extraocular muscles

Answer 5

horizontal movements: medial and lateral rectus muscles

vertical eye movements: coordinated action of superior and inferior recturs, and superior and inferior oblique

when eyes abducted (looking outward) the rectus muscles serves as the primary veritcal movers

Question 6

abduction

Answer 6

away from midline

Question 7

adduction

Answer 7

towards midline

Question 8

extraocular muscles are innervated by lower motor neurons in the brainstem

Answer 8

whose axons form 3 cranial nerves: the abducens nerve (lateral rectus in the ipsilateral eye), the trochlear nerve (superior oblique on contralateral side) and the oculomotor nerve (ipsilateral)

Question 9

gaze stabilising eye movements

Answer 9

vestibulo-ocular and optokinetic

Question 10

gaze shifting eye movements

Answer 10

saccades, smooth pursuit and vergence

Question 11

vestibulocular reflex

Answer 11

able to maintain stable fixation over some target in the environmetn

reflex response to automatically compensate for head movement

limited to relatively fast head movement

Question 12

optokinetic eye movements

Answer 12

• sensitive to global or fullfield visual motion produced by slow rotational movements
• stabilises the visual image on the retina

Question 13

vergence eye movements

Answer 13

align fovea of each eye with targets located at different depths

Question 14

Frontal eye fields

Answer 14

located in rostral portion of premotor cortex (Brodmann’s Area 8)

Question 15

Function of superior colliculus and the Frontal Eye Fields

Answer 15

play important roles in planning and initiating saccades to visual targets

Question 16

Frontal eye fields

Answer 16

direct route: FEF > PPRF

indirect route: FEF > SC > PPRF