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Eye Movements
Saccades
| Question | Answer |
|---|---|
| ________ saccades are voluntary changes of fixation between objects. | Volitional |
| ________ are components of other eye movement types: VOR fast phase, OKN fast phase, the pursuit "catch-up" saccades, and microsaccades of steady fixation | Saccades |
| 2 functions of the ________ saccades are to 1) explore the environment and objects within it 2) place objects of interest close to the fovea where high spatial resolution is possible. | Volitional |
| Stimuli: Saccadic system is both ______ and non______ stimuli | visual and non-visual |
| _______ stimuli include objects of interest, features and details important to the task, and novel or alarming visual stimuli. | Visual |
| _____-_____ stimuli include auditory stimuli, and the remembered locations of objects | non-visual |
| Categories of Saccades: 2 kinds ______ and ________ | Normometric, Dysmetric |
| ________ saccades consist of a single movement of the correct amplitude with suitable and swift dynamics | Normometric |
| _______ saccades are not normometric, for whatever reason | dysmetric |
| Single-step dysmetric saccades may be classified as ________ or _______. | hypometric or hypermetric |
| __________ saccade under-shoots the target. | Hypometric |
| _________ saccade overshoots the target. | Hypermetric |
| Saccades may be executed as multiple steps, and a multiple-step saccades measured by the first step are mostly ________. | Hypometric |
| Latency: Regular saccades have a latency of about _____-200ms for unpredictable stimuli. | 180 |
| A __________ saccade is the second, third, or later step in a multi-step saccade. | refixation *Have latency of about 150ms, which is shorter than for regular saccades! |
| Which other types of movements have saccadic components? | VOR Fast OKN Fast Pursuit catch-up Microsaccades of steady fixation |
| ______ space: if the error of eye fixation is less than about +/- 0.25 to 0.35 degree, then a saccade isn't initiated. | Dead |
| What are the 3 components of a saccade and what are their functions? | Pulse, Slide, Step |
| What is a ballistic system? | Once you decide to do something, you have no control over it |
| What are some characteristics of saccade velocity we can learn from the main sequence diagram? | saccade peak velocity and amplitude have a positive correlation |
| Gerald Westheimer showed that for a very brief ______ stimuli, the eye remained at the new position for at least ______ms before returning | pulse, 200ms |
| The saccadic system was modeled as a _____-data system, so the error in eye fixation is only ______ every 200ms. | sampled, sampled *target changes that occur between samples do not affect the response |
| Most saccades are less than ______ms in duration, and so could easily fit within the 200ms window for the sampled-data system. | 100ms *Possible that saccadic system is BALLISTIC (current research now says, not saccadic) |
| Example of ballistic system: (unrelated to eyes) | Shooting cannon balls b/c once it is shot, its course can't be altered |
| Some feedback does occur during the saccade in the form of ________ copy | efference |
| The _______ and _______ components of saccades control the dynamic part of the saccade, while the step holds the eye at the new fixation position. | Pulse, slide |
| The pulse and slide must generate a large ______ to 1) overcome opposing viscous and elastic forces within the orbital connective tissue and muscles and 2) provide a very high _______ acceleration | torque, angular |
| Ex. In the fastest saccades, the eye is accelerated to _______ deg/sec and then decelerated to a halt all within 100ms | 1000 |
| The _______ generates a brief strong force to move the eye | pulse |
| The ______ provides a brief force as a smooth transition to the step component. | slide |
| The ______ provides a small steady force to keep the eye in place. | step |
| The eye slows itself down due to visco-_____ biomechanical properties of the ______ tissues and muscles. | elastic, facial |
| Magnitude and Coordination: The saccade component must be of the correct amplitude and well-timed to obtain a ________ response | normometric |
| A _______ is a slow, sliding response to the final target position due to an initial over-shoot or undershoot of the pulse component | glissade |
| In normal individuals, most saccades can be classified as ________metric and ________metric. | normometric, hypometric |
| Normal for pulse to have an amplitude of 9/10 of the ________. | stimulus |
| Amplitude: Saccade amplitudes are usually less than _____ degrees | 15 |
| ______-head saccades are coordinated eye and head movements to achieve a change in ______. | Eye, gaze |
| Velocity: Saccadic peak velocity and amplitude are ________ correlated in a relationship shown by the _____sequence diagram. | positively, main ex. larger peak velocities associated with larger saccade amplitudes |
| It isn't possible to produce voluntary, exceptionally fast or slow saccades for a given _________. However, slow saccades occur in some neural conditions | amplitude |
| Duration: Saccades are very brief and almost always executed within ______ms | 100 |
| Directions of Saccades: _______ and _______ saccades are not handled by identical neural pathways and aren't always horizontal or vertical, respectively. | horizontal, vertical |
| During ________ saccades, the horizontal and vertical components don't have the same timing and velocity. | oblique Therefore, they are usually curved in space |
| Transient Vergence: Timing and velocity of _______ in the two eyes ARE/ARE NOT exactly matched. | saccades, are not NOT EXACTLY CONJUGATE |
| The ABDUCTING/ADDUCTING eye leads the ABDUCTING/ADDUCTING and arrives sooner. | abducting, adducting |
| A ________ divergence during the horizontal saccade occurs. | dynamic |
| At the termination of the saccade, small fixation disparities are corrected by the _______ system. | vergence |
| Prediction: Individuals learn to predict _______ motion very quickly and time their saccades accordingly. | target *latency of the saccade may be reduced, zero, or even be negative |
| Plasticity: A new or altered pair of glasses changes the relationship between the perceived direction of an eccentric object, and the actual point of __________ if the eye rotates to align on the initially perceived direction. | fixation |
| With anisometropic spectacle corrections, the saccades become DISCONJUGATE/CONJUGATE so that in space they are effectively DISCONJUGATE/CONJUGATE. | disconjugate, conjugate |
| Interactions: The vestibulo-ocular response must be suppressed during any saccade that includes correlated head movement like an _____-_____ saccade. | eye-head |
| Neural Control: Frontal Eye Fields (FEF) initiate ________ saccades and have ______topic organization | voluntary, retinotopic (there is a mapping between positions in the field of view and positions on the FEF |
| Activity in the Frontal Eye Fields leads to a horizontal saccade to the CONTRALATERAL/IPSILATERAL side. | contralateral |
| Activity in the frontal eye fields is required for a _________ saccade. | vertical |
| The ______ eye fields project to the superior colliculus (SC), paramedian pontine reticularl formation (PPRF), and rostral interstitial medial longitudinal fasciculus (riMLF). | Frontal |
| The superior ______ coordinates head and eye to fixate a particular direction in space and projects to the pontine reticular formation (PRRF) and rostral interstitial medial longitudinal fasciculus (riMLF). | colliculus |
| The pontine reticular formation (PPRF) contains premotor nuclei for ________ saccades, and the riMLF does so for ________ saccades. | horizontal, vertical |
| ______-motor neurons, in various sites are: burst neurons, and long-lead burst neurons; the omnipause cells; and tonic cells. | Pre |
| Long-lead burst neuron cells fire at _____ms. (BEFORE THE SACCADE) | 40 |
| ______-lead burst neuron cells fire at the start of and during the saccade. Two types: excitatory burst neurons and inhibitory burst neurons | medium |
| _______ burst neurons provide pulses to the agonist, while _______ burst neurons provide inhibitory off-pulses to the antagonist. | Excitatory, inhibitory **Example of SHERRINGTON'S LAW |
| Omnipause neurons fire ________ to inhibit burst cells. | continuously |
| _________ neurons stop firing just at the start of and during any saccade. (Act as GATEKEEPERS of the saccade system) | Omnipause |
| If omnipause neurons are stimulated experimentally, then voluntary saccades are ______________. | impossible |
| ______ cells fire after the saccade to maintain eye position and are part of the GAZE HOLDING MECHANISM (neural integrator) essential for accurate steady fixation. | Tonic |
| Why does dynamic vergence occur during a horizontal saccade? | Timing and velocity of eyes aren't exactly matched, abducting eye is slightly faster than adducting ,NOT TRULY CONJUGATE |
| What is the usual trajectory of an oblique eye movement in space? | Curved in space |
| How can someone produce a saccade BEFORE the target moves? | predictable, 0 latency |
| Describe how burst neurons (EBN and IBN), omnipause, and tonic cells cooperate with each other in the production of a saccade. | EBN- bursts from agonists IBN- inhibitory off-pauses of antagonist omnipause-fire continuously to inhibit burst cells, gatekeepers of saccade system b/c stop firing at the start of and during saccade Tonic-fire after saccade to maintain position |
| If you're looking before the focal point, you'll see ____ objects. | double |
Created by:
Jmdink