Eog

Question 1

What is the visual modality in humans?

Answer 1

Among the most important exteroceptive sensory modalities

Question 2

Where is the density of cones highest in the retina?

Answer 2

In the foveal area

Question 3

What is the significance of the foveal area?

Answer 3

It is where the highest visual acuity can be achieved

Question 4

What does the brain attempt to keep on the fovea?

Answer 4

The most salient part of the visual field

Question 5

How is fixation of an object in the visual field usually accomplished?

Answer 5

By moving the head and/or the eyes

Question 6

What term describes the movement of the eyes to track objects?

Answer 6

Visual tracking

Question 7

What are microsaccades?

Answer 7

Minor repetitive, involuntary, quick movements of the eyeball

Question 8

How can the overall activity of the eye muscles be controlled?

Answer 8

Voluntarily

Question 9

What are the muscles that move the eyeballs called?

Answer 9

Extrinsic eye muscles

Question 10

How many extrinsic eye muscles are there?

Answer 10

Six

Question 11

What is the role of cranial nerve VI?

Answer 11

Innervates the lateral rectus muscle

Question 12

What does stereo vision require?

Answer 12

Synchronized movements of the two eyeballs

Question 13

Fill in the blank: The _______ is responsible for the superior oblique muscle.

Answer 13

Trochlear nerve

Question 14

True or False: The movements of the eyeballs provide the brain with identical images.

Answer 14

False

Question 15

Which cranial nerve is associated with the oculomotor nerve?

Answer 15

Cranial nerve III

Question 16

What is the function of the extrinsic eye muscles?

Answer 16

To move the eyeball within the orbit

Question 17

What is the primary purpose of horizontal and vertical eye movements?

Answer 17

To maintain fixation on an object of interest

Question 18

What is the primary function of the motor centers located in the frontal lobe of the cortex?

Answer 18

Control of muscles

Includes the remaining four muscles of the eye.

Question 19

What is the physical structure of the human eyeball described as?

Answer 19

A dipole

Positive terminal in front of the cornea and negative terminal behind the retina.

Question 20

What potential is generated between the positive and negative terminals of the human eyeball?

Answer 20

Approximately 0.4-1.0 mV

Generated by hyperpolarizations and depolarizations of nerve cells in the retina.

Question 21

What does electrooculography (EOG) measure?

Answer 21

Movements of the eyeballs as voltage changes

Measured in terms of the potential difference generated by the eyeball’s dipole structure.

Question 22

How are horizontal movements of the eyeball measured in EOG?

Answer 22

By placing electrode pairs on the temporal side of the two orbits

Vertical movements are measured with electrodes above and below the right eye.

Question 23

What happens to the EOG signal when the eyeball is in the middle position?

Answer 23

The signal is close to zero

This occurs when the distance from both electrode pairs is equal.

Question 24

What induces a positive change in voltage in an EOG measurement?

Answer 24

Moving the eyeball horizontally closer to the positive electrode

The opposite movement induces a negative change in voltage.

Question 25

What is the typical accuracy of EOG measurements?

Answer 25

1.5-2°

The measurable range is up to 70° both vertically and horizontally.

Question 26

What is the range of EOG signal voltages?

Answer 26

0.05 to 3.50 mV

The frequency domain of interest for direction of gaze is 0-15 Hz.

Question 27

What occurs to EOG values under constant fixation?

Answer 27

They slowly return to baseline (zero) in several minutes

Indicates the stability of the measurement over time.

Question 28

True or False: Movement of facial muscles can introduce noise into the EOG signal.

Answer 28

True

Movement of the jaw can also contribute to artifacts in the signal.