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The vestibular labyrinth

The vestibular labyrinth. Hair cell responses . Neural pathways for the angular-VOR three-neuron arc. Vestibular latency i s about 15 msec. Eye movements: Lab # 1 - Catching a ball. How do we use our eyes to catch balls? What information does the brain need?

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The vestibular labyrinth

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  1. The vestibular labyrinth

  2. Hair cell responses

  3. Neural pathways for the angular-VOR three-neuron arc Vestibular latency is about 15 msec

  4. Eye movements: Lab # 1 - Catching a ball

  5. How do we use our eyes to catch balls? What information does the brain need? Most experiments look at simple movements in response to targets. What happens in the real world?

  6. Cricket

  7. Batsman anticipate bounce point Better batsman arrive earlier saccade pursuit Eye movements in cricket: Land & MacLeod, 2001

  8. Why are eye movements predictive? Analysis of visual signals takes a lot of time! Photoreceptors ganglion cells LGN Primary visual cortex other cortical areas mid-brain brain stem muscles Round trip from eye to brain to muscles takes a minumum of 200 msec. Cricket ball only takes about 600 msec. Prediction gets around the problem of sensory delays.

  9. Is prediction seen in cricket a general property of behavior, or only seen in skilled performance like cricket or baseball?

  10. X smooth pursuit saccade X Catching: Gaze Patterns X Thrower Catcher

  11. After three trials, pursuit has improved a lot. Implications of this?

  12. Different pattern of eye movements when watching (earlier, no pursuit). Implications of this?

  13. saccade X X Gaze Patterns Different when Watching X Thrower Catcher

  14. Lab groups

  15. What are the questions? • Is the behavior observed by Land in cricket also true for a simple task like catching a ball? • What eye movements are made in this case? • Do subjects anticipate the bounce point? By how much? • Does it correlate with performance? • Do Subjects look at floor or above the bounce point? • What happens after bounce? • What is the difference between throwing and catching? Why? • Similarity between individuals? • When do the hands start to move? • 2. Choice of task: • Catching and throwing a ball. • 3. Procedure: • Select subject and calibrate eye tracker. Two throw the ball back and forth, with a bounce in the trajectory at a comfortable distance. Need to measure the distance. • First throw in a predictable manner, about10 times.

  16. Data analysis • Play video frame-by-frame using Video-Viewer software. • …. • What to look for: • Describe eye movements sequence for each trial • eg Trial 1: fixate near hands/saccade to bounce point/fixate/track portion of trajectory/fixate for last part of trajectory (??) • Trial 2: fixate near hands/saccade to bounce point/fixate/track portion of trajectory/fixate for last part of trajectory (??) • …. • B How regular is the sequence of movements? • C What is the timing of the saccades/fixations/tracking relative to movement of the ball. How much do subjects anticipate the bounce point, if at all? • D. How accurate are fixations near the bounce point? (Need to measure visual angle.) • Compare different conditions. • What happens with the different balls? Do the eye movements change with additional experience? How quickly do they adjust? • What is the role of the pursuit movement? If pursuit is made only on final bounce, implies pursuit is used to guide hands. Maybe position of eye in head.

  17. Unexpected bounce leads to poor performance, particularly in the pursuit movement after the bounce. Implications of this?

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