Describe 2 kinds of eye movements and their function
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DESCRIPTIONDescribe 2 kinds of eye movements and their function. Describe the specialized gaze patterns found by Land in cricket. Describe your results in the ball-catching lab. How do they compare with Land s? What is meant by top-down and bottom-up processing? Give examples of both. - PowerPoint PPT Presentation
Describe 2 kinds of eye movements and their function. Describe the specialized gaze patterns found by Land in cricket.Describe your results in the ball-catching lab. How do they compare with Lands?What is meant by top-down and bottom-up processing? Give examples of both.Give some examples that reveal attentional limitations in visual processing.What is Neuroeconomics? Explain how the saccadic eye movement circuitry is influenced by reward.Give some examples that eye movements are learned.Describe the Sprague and Ballard theory (Walter) of gaze control. What evidence is there to support the theory. Why is it useful?Draw a sketch of the brain showing the structures involved in the generation of a saccadic eye movement. Specify the function of these structures.
Describe 2 kinds of eye movements and their function.
Types of Eye MovementInformation GatheringStabilizingVoluntary (attention)Reflexive
Saccadesvestibular ocular reflex (vor)new location, high velocity, ballisticbody movements
Smooth pursuitoptokinetic nystagmus (okn)object moves, velocity, slow whole field image motion
Vergencechange point of fixation in depthslow, disjunctive (eyes rotate in opposite directions)(all others are conjunctive)Fixation: period when eye is relatively stationary between saccades.
Why do we move our eyes? High density of cone photoreceptors in central fovea - also high acuity
Describe the sequence of eye movements you might make inan everyday task eg making breakfast. Describe the functionof each movement.
Making breakfast:Upon entering the kitchen: saccade to the cupboard on the basis of memory, as I know cereal is located there. Approach cupboard and saccade to door handle to guide hand to open door. Search for cereal with several saccades, maybe landing on boxes of similar size and appearance. When saccade lands on the correct box, stay fixating to guide the grasp of the box. Rotate body and head to exit the cupboard and make a big saccade to the cupboard containing the bowls. Fixate the cupboard while I walk there and make a fixation to the handle to guide opening.
Describe the specialized gaze patterns found by Land in cricket.
Eye movements in cricket:Land & MacLeod, 20011) Batsman fixates the bowlers hand
2) Makes a saccade to the anticipated location of the bounce. 3) This is followed by a smooth pursuit movement after the bounce.
The bounce point gives information about where and when to swing the bat.
Describe your results in the ball-catching lab.Did you find the same basic pattern as Land did?How did your results differ?
Catching: Gaze PatternsCatcherThrowerX
Draw a sketch of the brain showing the structures involved in the generation of a saccadic eye movement. Specify the function of these structures (to the extent that this is possible)
(LIP) target selectionsignals to musclesInhibits SC saccade decisionSaccade commandmonitor/plan movementsGeneration of SaccadesV1 (image)
Photoreceptors ganglion cells LGN
Primary visual cortex SEF/FEF, PF Cortex
Basal ganglia (caudate/SNc) SC/mid-brain
brain stem (Reticular formations) oculomotor groupsRetina to Saccade
Photoreceptors ganglion cells LGN
primary visual cortex posterior parietal ctx
pre-motor ctx M1 musclesWhy is prediction necessary?Components of visuo-motor latency.Round trip from eye to brain to muscles takes a minumumof 200 msec. Ball (our expt) only takes about 900 msec.Prediction gets around the problem of sensory delays.
What is meant by top-down and bottom-up processing? Give examples of both.
Bottom up processes are evoked by the visual stimulus.
Top down processes are operations that reflect the subjects current cognitive goals.
In the case of eye movements, fixations that are for the purpose of getting specificinformation to accomplish a task are said to reflect top down control.
Fixations that are evoked automatically by the occurrence of a stimulus are said tobe under bottom up control.
What is Neuroeconomics? Explain how the saccadic eye movement circuitry is influenced by reward.
Humans/primates exhibit behaviors that lead to expected reward. Reward is provided by the release of dopamine.
Dopaminergic neurons in basal ganglia signal expected reward. (Schultz, 2000)Response to unexpected rewardIncreased firing for earlier or later rewardExpected reward is absent.SNpc
Neurons at all levels of saccadic eye movement circuitry are sensitive to reward.
LIP: lateral intra-parietal cortex. Neurons involved in initiating a saccade to a particular location have a bigger response if reward is bigger or more likely
SEF: supplementary eye fieldsFEF: frontal eye fieldsCaudate nucleus in basal ganglia
This provides the neural substrate for learning gaze patterns in natural behavior, and for modeling these processes using Reinforcement Learning. (eg Sprague, Ballard, Robinson, 2007)
Give some examples that eye movements are learned. Jovancevic & Hayhoe 2009 Real Walking
Learning to Adjust GazeChanges in fixation behavior fairly fast, happen over 4-5 encounters (Fixations on Rogue get longer, on Safe shorter)
Time fixatingIntersection.Follow the car.orFollow the car and obeytraffic rules.CarRoadsideRoadIntersectionShinoda et al. (2001)Detection of signs at intersection results from frequent looks.Top Down strategies: Learn where to look
Give some examples that reveal attentional limitations in visual processing Difficult to detect color change in one of 8 colored squares.
Color-changing card trick
What are these examples called?
What conclusions has been drawn from these experiments.
*Now we should review the major types of eye movements Mediated by different brain areas which well review on thursday*This is basically the same graph but also demonstrates that the level of acuity (Ie the sharpness of objects)Is best and falls off drastically in the peripheryPeak acuity - can distinguish lines separated by a photoreceptor width.*Show - Not confined to expert cricketers- general aspect of behav
*****21What do we know? Previous work on dsn of attn in natural environments: