NSCI 324*Systems Neuroscience

Doug MunozCentre for Neuroscience StudiesBotterell Hall, room 226x32111doug.munoz@queensu.ca

Tutorial: Monday Jan 23, 2012 10:30amBotterell B147TA: Jay Jantz (j.jantz@queensu.ca)

NSCI 324*Systems Neuroscience

Vision and Oculomotor Control (Dr. Munoz)January 10 The retina January 13 Central Visual PathwaysJanuary 16 Dr. Munoz Tutorial: January 16 Higher Visual functions January 17 Oculomotor System I. Basic organization January 20 Oculomotor System II. Vestibulo-ocular reflexJanuary 23 Dr. Munoz tutorial:January 23 Oculomotor System III. SaccadesJanuary 24 Basal Ganglia for cognitive and motor controlJanuary 27 review of Dr. Munoz lecture materialJanuary 30 Dr. Munoz exam in tutorial period

Oculomotor system I.Basics

Movements that stabilize the eye when the head moves

Movements that align the fovea with a visual target

Movements that stabilize the eye when the head moves

Movements that align the fovea with a visual target

Vestibulo-ocular

Vestibulo-ocular Reflex

Movements that stabilize the eye when the head moves

Movements that align the fovea with a visual target

Vestibulo-ocular

Optokinetic

Movements that stabilize the eye when the head moves

Movements that align the fovea with a visual target

Vestibulo-ocular

Optokinetic

Saccade

Visual Fixation

Saccades allow us to scan the visual field and intermittently focus our attention on the parts of the scene that convey the most significant

information.

Saccade-Fixation Behaviour

Eye movements reveal a good deal about the strategies used to inspect a visual scene. Each scan reflects the current task.

Free examination

An Unexpected Visitor (I.E. Repin)

Gaze position

What do Saccades Accomplish?

Instruction: “Give the ages of the people.”

An Unexpected Visitor (I.E. Repin)

What do Saccades Accomplish?

Instruction: “Remember the clothes worn by the people.”

An Unexpected Visitor (I.E. Repin)

What do Saccades Accomplish?

Instructions: “Remember the position of the people and the objects in the room.”

An Unexpected Visitor (I.E. Repin)

What do Saccades Accomplish?

Instruction: “Estimate how long the unexpected visitor had been away from the family.”

An Unexpected Visitor (I.E. Repin)

What do Saccades Accomplish?

The human eyes voluntarily and involuntarily fixate on those elements of a visual scene that carry essential and useful information. The more

information is contained in an element, the longer the eyes stay on it.

The distribution of fixations on the elements of a scene changes depends on the purpose of the observer, i.e., it is determined by information to be

obtained and the thought process accompanying the analysis of this information.

Hence people who think differently also, to some extent, see differently.A.L. Yarbus (1967)

What do Saccades Accomplish?

Movements that stabilize the eye when the head moves

Movements that align the fovea with a visual target

Vestibulo-ocular

Optokinetic

Saccade

Visual Fixation

Smooth Pursuit

Movements that stabilize the eye when the head moves

Movements that align the fovea with a visual target

Vestibulo-ocular

Optokinetic

Saccade

Visual Fixation

Smooth Pursuit

Vergence

Vergence

Fixate far target Fixate near targetVergence: eyes move in opposite directionsConvergence: to fixate near objectsDivergence to fixate far objects

Retinal Disparity Drives Vergence Eye Movements

Retinal disparity: difference in location of image between the two eyes. Disparity signal is derived in extrastriate cortex (dorsal stream)

Extraocular Muscles

Extraocular Muscles

Extraocular Muscle Innervation

The Oculomotor and Trochlear

nerves originate from the midbrain.

The Abducens nerve originates from the pons.

Lateral view

Discharge Properties of Motoneurons

Properties of MotoneuronsF

iring

Fre

quen

cy

Eye Position (E)

Firi

ng F

requ

ency

Eye Velocity (E)

Extraocular Muscle Motoneurons

carry eye position and eye velocity

final common path for all eye movements

integrator located in reticular formation and vestibular complex of brainstem part of final common path

“Neural integrator” integrates E command to produce E command

muscleMNE + E

E

+

E +