NSCI 201 Chapter Notes - Chapter 20: Cranial Nerve Nucleus, Medial Rectus Muscle, Extraocular Muscles

50 views9 pages

For unlimited access to Textbook Notes, a Class+ subscription is required.

NSCI 201 (18.20)
Eye mvmt/ Sensorimotor Intg
22nd March 2016
Eye Movement and Sensorimotor Integration!
!
Eye movements!
!
Conjugate (eyes move in the same direction)!
!
!Saccadic: rapid, ballistic movements that change point of fixation!
!
!Smooth pursuit: slower tracking motions to keep moving stimulus on fovea!
!
!Vestibulo-ocular, optokinetic: Stabilization to compensate for head/ body movements!
!
Disconjugate (eyes move in opposite directions)!
!
!Vergence movements: Align fovea of each eye to targets at different distances!
!
!
!
!
!
!
!
!
Example: The perception of stabilised retinal images!
This setup ensures that image is always projected on fovea—after a while, image actually
disappears due to receptor fatigue, and editing. We’re always looking at things even if we don’t
feel like we are— eyes make tiny movements and saccades to track background imagery.!
!
!
!
!
!
!
1
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 9 pages and 3 million more documents.

Already have an account? Log in
NSCI 201 (18.20)
Eye mvmt/ Sensorimotor Intg
22nd March 2016
!
Six pairs of extra-ocular muscles contribute to vertical and horizontal eye movements!
Recall: lateral and medial recti move eyes in medial-lateral plane. These movements are also
called adduction (toward nose), abduction (towards temples) Also involved in vergence
movements. !
!
Vertical movements are due to superior and inferior recti.!
!
Torsional movements due to superior and inferior obliques. Intorsion: rotation of eye from top
towards nose; extorsion (away from nose)!
!
!
Innervation of the extra ocular muscles by the cranial nerve nuclei governing eye
movements!!
!
!
Oculomotor nucleus: situated in midbrain, controls
4 of 6 pairs of muscles, as well as pupils and
eyelids. Output through cranial nerve III. !
!
!
Trochlear nucleus is the only contralateral
innervation, runs through cranial nerve IV to control
superior oblique. !
!
!
Abducens nucleus controls lateral rectus, runs
through cranial nerve VI!
!
!
These are proximal connections, controls tensions
of individual muscles when firing occurs. !
!
!
!
!
!
2
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 9 pages and 3 million more documents.

Already have an account? Log in
NSCI 201 (18.20)
Eye mvmt/ Sensorimotor Intg
22nd March 2016
!
The metrics of a saccadic movement!
200 ms delay between shift in target position and saccade onset. !
!
Motor neuron activity in relation to saccadic eye movements!
Bursts of firing during saccadic movements, especially immediately preceding movement.
Duration of bursting roughly corresponds to duration of movement. Firing is suppressed when
saccade is produced in other direction.!
!
!
Metrics of smooth pursuit movements!!
!
!
Tracking is smooth up to a certain speed— can
perform catch-up saccades if lagging. !
!
!
!
!
!
!
!
!
!
!
3
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 9 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class