W5 - Vision in sport Flashcards
What is the function of:
- cornea
- pupil
- lens
- retina
- Cornea - where light enters the eye
- Pupil - is an aperture(hole where light enters). Intraocular muscles can change the size of the pupil to vary light entering. Dark = dilation, bright = constriction.
- Lens - changes shape(thicker or thinner) to refract light to focus our vision
- Retina - where all light/photoreceptors are, point were light focuses on the back of the eye. 2 types of cell(rods- dim light & central and peripheral field and cones- bright light & central visual field). These convert light into electric signals via optic nerve to be processed to the brain
What is meant by bioccular vision?
- 2 eye vision, so light from same thing will enter each eye at a slightly different angle, useful for depth perception(left & right half)
- Nasal nearer to nose(medial), temporal(lateral- optic tracts do not cross over)
- Nasal visual hemispheres cross over in the brain
- The difference in perception in visual field can be used to indicate how far away something is
What are the 2 types of eye movement?
fixations: fixating on something
More than 0.1 of a second
* central visual field (within 3°)
* duration 100 ms or longer
* conscious processing
saccades: jumping of eye movement
* rapid eye movements
* between fixations
* information is suppressed, as short
Time-period
What are the main visual streams (Norman, 2002)?
Visual streams:
focal vision (ventral):
* Identification (“what?”)
* central visual field
* conscious
ambient vision (dorsal):
* optical flow - movement of info along optic nerve(“where?”) = quicker(subconscious)
* central & peripheral visual field
* nonconscious
How can vision be trained in sport?
- Targets visual functioning of the eye (e.g. the lens, extraocular muscles) through to the visual cortex and association area of the occipital lobe
- These skills can assist the athlete in the detection and identification of visual stimuli (e.g. localizing a tennis ball during its trajectory), discrimination (e.g. separating the tennis ball from a yellow cap worn by a crowd member)
- Defined by the consistent use of generic stimuli
What visual stream goes to the:
- parietal lobe
- temporal lobe
- dorsal stream (“where”)
- ventral stream (“what”)
Then both go to frontal where we plan a response, then to cortex to carry it out
what is the time course of visual streams?
1) Occipital lobe –> wither dorsal(parietal lobs) or ventral(temporal lobe) stream
2) Dorsal + ventral to frontal lobe = response planning
3) Frontal lobe –> (pre)motor cortex = specific movements organised
4) (pre)motor cortex to spinal cord
How is Tau determined when:
- moving observer
- moving object
- As something comes closer to you it takes up more of your visual field(looks bigger)
- Closer object gets bigger, number of rods & cones can be an indicator of how big something is/time to contact
How is Tau determined?
Tcontact = size of image/rate of expansion
Tcontact is inversely proportional to the rate of expansion
Provide example studies of Tau:
- Bootsma & van Wieringen, 1990 (table tennis example)
- Lee et al., 1982 (long jump example)
- Sayyah et al., 2018 (diving example)
describe interceptive tasks:
- Image direction on retina
- same on both eyes → miss to that side
- less speed difference → pass wider
If moving to right, object is moving to my left (or I’m moving the right)
Describe the run to catch/intercept task (objective):
Solution:
* couple running speed to rate of change of tau
* tau-dot 𝝉’ = rate of change of tau
* stop just short: keep -0.5 < τ’ < 0
* hit while moving: keep -1 < τ’ < -0.5
A negative number closes the gap (catch an object). If size changes of an object as it comes towards you, it generally leads to failure in the task. Based on learning to catch based on the size of something in your visual field.
Describe the interceptive timing task (moving pointing finger to intercept a ball on screen): SATO
- Easier to be accurate in timing with something moving fast, than slow
- Easier to time maximal movements because potentially only 1 max, a lot of different ways to reach e.g.: 50%
Define:
- advance cue utilisation
- temporal occlusion
- Advance cue utilisation - athletes ability to make accurate predictions based on contextual info
- Temporal occlusion - varying the extent of the shown ball flight info, with 42ms before impact having the biggest impact on success rate
- Limitation - approach does not tell us about the nature of the anticipatory cues the performer uses in the anticipation process
What was shown by (Muller& Abernethy, 2006) on batters cue utilisation?
- occlusion studies on batters (reaction time paradigms)
- Varying the time at which info is available
- With no occlusion, both are successful
- All players track ball after release, occlusion pre-bounce = bigger gap but both successful
- So info after bounce is only useful if they got the first prediction wrong
- Pre-release = higher skilled are able to do it, LS were not. HS players are able to use info before release (can be trained)
