Eye-Movements and Eye-Tracking

Question 1

Video-Based Eye Tracking

Answer 1

Reflect infrared light at the eye and recording pupil and cornea position
Static systems: higher accuracy, high control over stimulus presentation
Mobile systems: totally mobile so useful for everyday life, lower accuracy, less control over stimulus presentation

Question 2

Why Do The Eyes Move?

Answer 2

Brings fovea in line with visual stimuli
Fovea has greatest acuity
Moved by extraocular muscles
Gaze position is usually tightly couple with attentional selection

Question 3

4 Types of Eye Movements

Answer 3

Saccades: fat, jump like movements
Fixations: stationary period between saccades
Pursuit: smooth tracking of target object
Vergence: keeps both eyes on a target which changes in depth

Question 4

Drifts and Microsaccades in Fixations

Answer 4

Act to refresh the image on the retina

Avoids fading of image caused by adaptation of retinal photoreceptors

Question 5

Saccadic Orienting

Answer 5

Eyes move to bring parts of scene most relevant into highest acuity
Originally thought of as a dichotomoy

Question 6

Superior Colliculus

Answer 6

The most lateral layers have receptive fields that respond to visual stimuli
Intermediate layers contain multisensory and motor neurons
Each map (visual, motor etc) aligned with the others in topographic space
Sensory and motor maps integrated which allows coordinated movements to stimuli in the environment

Question 7

Wurtz & Goldberg (1972) Monkeys and Superior Colliculus

Answer 7

Electrical stimulation of neurons caused saccades with a particular movement field
Visuomotor neurons in the intermediate layers of the SC activated by visual stimuli at particular locations
Activation in some neurons when covertly attending to stimulus (no eye movement)

Question 8

What is the Antisaccade Task?

Answer 8

Studies reflexive and voluntary saccades and cog inhibition
Enables decoupling of stimulus encoding and response preparation
Can be used to study deficits in cognitive control resulting from lesions and psychiatric disorders

Question 9

Antisaccade Task Procedure

Answer 9

Look in the opposite direction to the target
A stimulus onset causes a reflexive saccade
To look away the saccade must be inhbited and the correct saccade must be voluntarily programmed in the other direction
Reflexive saccades are faster than voluntary saccades
Healthy controls make around 10% errors

Question 10

Cognitive Controls Used in Antisaccade Task

Answer 10

Inhibit the prosaccade
Determine correct location for the antisaccade
Voluntarily make the antisaccade