ELECTROOCULOGRAPHY
Dep. of Physiology, Fac. of Medicine, MU, 2016 © Zuzana Nováková
ELECTROOCULOGRAPHY
• Method for assesment of the eye movements employing the
measurement of potential difference between cornea and retina
• This potential generates an electric dipole oriented in parallel with
the optical axis of the eye
• The main goal of eye movements: to maintain and stabilize the object
of interest at the point of the sharpest vision (yellow spot)
Types of eye movements
• Sustaining (miniature) – such as fixation - Looking into our eyes do not stray far
away in space, but they are automatically fixed on a point in space (its visual field)
• Smooth pursuit movements - assist the macular stabilization of the observed
object
• Saccadic movements – assist the transferring the view to a new object
• Nystagmus – rhythmic eye-bulb movements, with 2 components: slow deviation to
one side and fast twitch to the opposite side (slow is vestibular, fast from brainstem
structures)
• Vestibulo-ocular reflex – stabilization of the retinal image during sudden, nonuniform
movements of the head
• Optokinetic nystagmus – regular eye movement stabilizing the view during slight
movement of the head or when the object changes its position with respect to
motionless head
Function of Eye
Movement
Type of Eye Movement
"Holding" (slow)
•Smooth Pursuit
•Optokinetic Nystagmus
(slow phase)
•Vestibular Nystagmus
•Convergence
•Divergence
•Accommodative Vergence
"Catching" (fast)
•Saccades
•Optokinetic Nystagmus
(quick phase)
"Sustaining"
(miniature) •Microsaccades •Tremor
•Drift
voluntary eye movement; involuntary eye movement
Eye Movement
The Vestibular Apparatus
•The vestibulo-ocular and optokinetic reflexes are the earliest eye
movements to appear phylogenetically
•The vestibulo-ocular reflex (VOR) stabilizes retinal images during
head motion by counter-rotating the eyes at the same speed as the
head but in the opposite direction
Characteristics of the VOR
The VOR stabilizes retinal images during brief head movements by counter-rotating
the eyes at the same speed as the head but in the opposite direction
Summary of Central Control of Pursuit Eye
Movement
Vertigo
Nystagmus
Dep. of Physiology, Fac. of Medicine, MU, 2016 © Zuzana Nováková
Vertigo
• Vertigo (dizziness)– subjective loss of stability in space, rotation of
surrounding space or rotation of body in space
• connected with objective symptoms – disturbances of equilibrium
and nystagmus – by stimulation of the labyrinths
• semicircular canals are stimulated by:
• rotation - post-rotational vertigo
• Caloric (application of external auditorial tube either with cold=27°C or
warm=47°C water
• electric current - galvanic vertigo
Nystagmus
• rhythmic eye-bulb movements, 2 components: slow deviation to one
side and fast twitch to the opposite side
• slow is vestibular, fast from brainstem structures
• Nystagmus at rest – vestibular system is affected by some
pathological process or cerebellum
Vestibular System: Structure
11
Vestibular System: Structure
12
utricle
saccule
Otolith
organs
Semicircular canals: structure
13
 each semicircular canal
contains an ampulla
 Contains hair cells
embedded in sensory
epithelium called crista
ampullaris
 Cilia of hair cells
project into gelatinous
cap called cupula
Enlargement of
ampulla
Crista ampullaris
Semicircular
canals
Semicircular canals:
function
14
 Specialized for responding to rotational
acceleration of the head
 Head rotation results in the
movement of endolymph in opposite
direction
 Bends cupula which bends hair cells
 Same mechanical/electrical
coupling as in auditory hair cells
B&B Figure 13-18
Semicircular canals: sensory transduction
15
B&L Figure 8-26
 Steriocilia maintain directionality on both sides of the head
 Bending towards kinocilium  opens mechanically gated cation
channels  K+ influx  depolarization
 Bending away from kinocilium  closes channels that are open during
resting state  hyperpolarization
Semicircular canals: sensory transduction
16
Kandel Figure 40-7
 Paired canals work together
to signal head movement
 With turning of the
head, hair cells on one
side of the body send
excitatory signals to the
brain while hair cells on
the opposite side are
inhibited
Vestibular Pathways
17
• vestibular afferents synapse on vestibular nuclei located in medulla & pons
• Nuclei integrate information from vestibular, visual, and somatic receptors and send collaterals to
• 1.cerebellum
• Sends corrective adjustments to motor cortex: maintenance of balance and posture
Vestibular Pathways
18
• 2.nuclei of cranial nerves
• Control coupled movements of the eyes, maintain focus and visual field
• 3.nuclei of accessory nerves
• Control head movement and assist with equilibrium
Vestibular Pathways
19
• 4.ventral posterior nucleus of thalamus and vestibular area in cerebral cortex (part
of primary somatosensory cortex)
• Conscious awareness of the position and movement of head
Areas 1,2,3
Vestibular Reflexes
20
Vestibulospinal Reflexes
• Senses falling/tipping
• contracts limb muscles for postural support
Vestibulocollic Reflexes
• acts on the neck musculature to stabilize the head if body
moves
Vestibulo-ocular Reflexes
• stabilizes visual image during head movement
• causes eyes to move simultaneously in the opposite direction
and in equal magnitude to head movement
Summary of Central Control of Saccades