Saccades Flashcards
Velocity
The speed at which an object is traveling
Amplitude
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
Saccade latency can be thought of as the composite of time during which the following occurs…
- Processing of visual stimulus
- Accumulation of a decision process
- Final motor execution
What is the amplitude of saccades in normal viewing situations and at ever degree does head movement become involved?
In normal viewing situations most Saccades have an amplitude of >15 degrees, after which the head becomes involved in the movement to redirect the eye.amplitude situations
Saccadic interval
The duration of time between the event that is being responded to—for example a peripheral visual flash—and the onset of movement (Gilchrist, Oxford p 87).
Same as saccadic latency (?)
The distribution of individual saccade latencies has a distinctive form. What is it?
The distribution of individual saccade latencies is SKEWED, with a longer tail for longer latency Saccades.
How is saccadic latency measured?
By using the simple transformation of “latency” for the RECIPROCAL of latency.
What type of distribution does the transformation of latency for the reciprocal of latency result in?
A distribution that is close to a Gaussian (normal) distribution (Gilchrist, Oxford p. 87-88).
What is L.A.T.E.R.?
Linear
Approach to
Thresholds with
Ergodic
Rate
- What does the LATER model measure?
- Who created the LATER model?
- This model involves a DECISION SIGNAL which has some starting level and then accumulates over time towards a THRESHOLD.
- Carpenter (1995)
How does LATER measure the decision process involved in making a saccade?
Once a decision threshold is reached, then the saccade is generated.
What creates for the form of VARIABILITY in latency?
Trial-by-trial variability in the ACCUMULATION RATE of the decision signal.
What is an express saccade? What does an express saccade depend on?
A second (bimodal) distribution of Saccades which occur faster than normal and which may emerge depending on:
1. The amount of practice
2. The presence of a gap
3. The position of the target?
What is the Gap effect in saccades?
A reduction in the saccadic latency if the currently fixated item disappears before the new target appears (in a simple saccade test).
What is a “reflexive pro saccade”?
An automatic response triggered by the sudden appearance of a peripheral stimulus. Unconscious.
What is an antisaccade? How are they different than reflexive prosaccades?
The ability to respond effectively to change in our visual environment; this hinges on our ability to make VOLUNTARY eye movements. These voluntary movements depend most on endogenous factors (top-down regulation).
What are two possible outcomes for antisaccades?
- A reflexive prosaccade driven by stimulus driven properties.
- Successful voluntary saccade is made.
What purpose do the occulomotor pathways serve?
Occulomotor pathways direct your eyes to a target of interest and keep them there even if the target is moving.
What purpose do the occulomotor pathways serve?
Occulomotor pathways direct your eyes to a target of interest and keep them there even if the target is moving.
What are the 4 main systems used by the oculomotor pathways?
- Saccades
- Pursuit
- Vergence
- Vesitubulo-ocular reflex
What is Dead Time? What happens directly dead time?
Immediately before each saccade’s execution, as a consequence of sensory transduction and motor pathway delays (5), there is a “dead time,” an ≈100-ms time interval in which visual information does not influence the destination of the saccade. This may be referred to as a PERIOD OF NO RETURN.
The oculomotor system enters a PERIOD of NO RETURN when the system is committed to be a given movement—either the saccade target either changes or moves (Gilchrist, p 89).
What is the difference between Dead Time, the Gap effect, the Remote Distractor effect, the Global Effect, and saccadic latency?
Dead time-/a period of no return when the saccade movement is conjured to a specific location even when the target changes or is moved.
Gap effect—a reduction in saccadic latency when the currently fixated item (in a simple saccadic study) disappears before the new target appears.
Remote Distractor Effect—an increase in saccadic latency when the target is presented concurrently with a distractor that is > 20 degrees off the target axis.
Global Effect—no increase in saccadic latency, but the placement of a distractor (>20 degrees off target axis) affects the location of where the saccade lands—between the target and the distractor.
Saccadic latency—Each saccade is the result of a neural decision that is based on the processing of visual information.
What is the Global Effect?
No increase in saccadic latency, but the placement of a distractor (>20 degrees off target axis) affects the location of where the saccade lands—between the target and the distractor.
What is the Remote Distractor Effect?
An increase in saccadic latency when the target is presented concurrently with a distractor that is > 20 degrees off the target axis.
- What is saccadic suppression? 2. What does it accomplish?
- The visual system shutting down retinal input during a saccadic eye movement.
- Saccadic suppression helps maintain our sense of visual stability so that eye movements don’t cause motion blur on the retina.
