Lecture 3d: Eye Movements Part 2 - Saccades Quiz

Saccades

The fast eye movements that place the retinal image of the object of interest on the fovea.

Reading Eye Movements

Typical eye movements made while reading, showing

fixational pauses (F), interfixational saccades (S) and a

regressional movement (R).

fixational pauses

Typical eye movements made while reading

what is F?

regressional movement

Typical eye movements made while reading

what is R?

interfixational saccades

Typical eye movements made while reading

what is S?

saccades

Amplitude and frequency of what depend on the skill of the reader and the difficulty of the reading matter?

amplitude, frequency

What of saccades depend on the skill of the reader and the difficulty of the reading matter?

Developmental Eye Movement Test (DEM)

Comparison data for children aged 6-13 yr. Use if suspect decreased reading skills are due to eye movement problem.

Task: say the numbers out loud, down a line, then across the line

The time to complete the task is timed; any errors made add to the

time score (there is a formula for this)

saccades

What is the Developmental Eye Movement Test (DEM) testing?

at least 100-200ms

what is the latency of the Saccades?

decreased

How is the latency of saccades affected by anticipation?

from anticipation

How is the latency of saccades decreased?

1 degree

What is the minimum amplitude of a saccade?

~100 degrees

What is the maximum amplitude of a saccade?

~15 degrees

What amplitude do most saccades occur in?

20 degrees

Greater than what amplitude usually results in 2 saccades and/or head movement?

a

Greater than 20 deg movements, there are 2 saccades where the first saccade is...

a) 90% of movement

b) 10% of movement

b

Greater than 20 deg movements, there are 2 saccades where the second saccade is...

a) 90% of movement

b) 10% of movement

~7-900deg/sec

the peak velocity of a saccade is?

50ms

the maximum duration of a saccade is?

b

The duration of a saccade is longer for...

a) smaller saccades

b) larger saccades

a

The duration of a saccade is shorter for...

a) smaller saccades

b) larger saccades

Retinal blurring

What is not noticed during a saccade?

Elevation of visual threshold by ~0.5 log units (visual suppression)

~0.5 log units

Retinal blurring is not noticed during a saccade, elevation of visual threshold by how much (visual suppression)?

motion blur

There is an absence of a perception, namely not perceiving your own saccades under normal circumstances. This mechanism is used to suppress what during saccades?

15 degrees

More than 85% of saccades have amplitudes greater than what?

85%

More than what percent of saccades have amplitudes greater than 15 degrees?

amplitude

Saccade duration increase as what increases?

large saccades

Peak velocity starts to level off for what?

automatic

Voluntary eye movements (we can choose to look at something or not), once initiated their execution is...

vision

Saccade is so fast there is no time to use what to guide the eye to its final position?

Saccades

What is so fast there is no time to use vision to guide the eye to its final position?

they are very fast, they are fast,

For saccades, there is no time to use vision to guide the eye to its final position because?

final position

Saccade is so fast there is no time to use vision to guide the eye to its...?

Saccade control system must calculate in advance the muscle activation required.

Slight over shoot, small corrections (corrective saccade)

Saccade is so fast there is no time to use vision to guide the eye to its final position. Saccade control system must calculate in advance the muscle activation required.

Resultant movement is pre-programmed or ballistic therefore what is common for saccades?

overcome eye's inertia (orbital viscous drag)

Saccades are produced by burst of neural activity, then train of impulses. The initial burst is for what?

velocity required

Pulse related to what of the saccade?

pulse

what related to velocity required for the saccade?

saccade amplitude

Size of step determines what?

burst neurons (in the brain stem)

Each saccade is associated with a burst of activity initiated from?

step

The size of what determines saccade amplitude?

tonic neurons (in the brain stem)

At the new position there is a tonic position-related discharge, controlled by?

duration of saccade

Duration of pulse determines what?

Frontal cortex

Saccades Are Controlled by the?

duration of pulse

What determines duration of saccade?

frontal cortex

The saccades are driven by what?

A decision and choice is required to initiate the saccade.

superior colliculus

Cortex controls saccadic system through the?

Amplitude

The size of the saccade, measured in degress or min of arc.

Peak Velocity

The highest velocity reached during the saccade. Saccade velocity profiles are usually symmetrical at least for small and medium size saccades.

Duration

Time taken to complete the saccade. Partly because of the high velocities involved, most saccades are complete within a few tens of milliseconds.

Latency

Time taken from the appearance of a target to the beginning of a saccade in response to that target.

Saccadic Suppression

The phenomenon where the brain selectively blocks visual processing during rapid eye movements.