Slide 1Best Action film clipPerceptual theoriesInverse projection problemPerception reconsideredPerceptual experimentsQuestion:Optic flow and a gradient of flowSlide 9Some important characteristics of optic flowOptic flow helps keep your balanceFlow, Posture, and BalanceThe Physiology of NavigationSlide 14Skilled ActionsPhysiological Links Between Sensory and Motor FunctionsSlide 17Experiment by Schindler et al.Slide 19Slide 20ResultsInterpretationVisual dominant vs. motor dominant neuronsMirror neuronsSlide 25Slide 26Slide 27What are mirror neurons for?Slide 29Creating action by activating motor cortexch 7 1Sensation & PerceptionCh. 7: Perception and Action© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)Main topicsEcological approachOptic flowThe physiology of navigationSkilled actionLinking sensory and motor functionsMirror neuronsBest Action film clip•Just in case, if you were not part of the history–http://www.youtube.com/watch?v=ijXJRcAmImk&feature=relatedch 7 2Perceptual theories•Many perceptual theories are about integrating top-down and bottom-up processes–Helmholtz’s unconscious inference–Likelihood principleInverse projection problemBottom-up information is not enough to create 3D perception.ch 7 5Perception reconsidered•J. J. Gibson’s ecological approach–All the studies we have seen so far are conducted in laboratory settings, in which stationary stimuli were given. –Perception is not a stationary experience.–Perception should be studied as it occurs in the natural environment.Perceptual experiments•Muller Lyer Illusion•Attention blink•Visual searchch 7 7Question:•What information do perceivers use as they move through the environment?•One type of information is:–Optic flow•E.g., expansion/contraction of a scene (an optic array that reaches the retina).–We notice the ratio of expansion/contraction (a gradient of flow).ch 7 8Optic flow and a gradient of flow•A gradient of flow gives a strong cue for motion and depth perception.–How much the scene expands on your retina gives you enough information to capture depth perceptionch 7 9Demonstration:http://www.reading.ac.uk/arl/clips/demo_of_displays.htm#opticflow http://www.youtube.com/watch?v=ysGM3CfBVpU&feature=relatedch 7 10Some important characteristics of optic flow•Invariant information–Gradient information remains constant under different conditions.–E.g., texture gradientch 7 11Optic flow helps keep your balance•Demonstration:–Stand up and raise one foot, and stay balanced while your eyes closed.–Isn’t it difficult?ch 7 12Flow, Posture, and Balance•Experiment by Lee and Aronson–13- to 16-month-old children placed in “swinging room”•In the room, the floor was stationary but the walls and ceiling swung backward and forward•The movement creates optic flow patterns–Children swayed forward in response to the flow patterns created in the roomch 7 13The Physiology of Navigation•Optic flow neurons - neurons in the medial superior temporal area (MST) of monkeys respond to flow patternsch 7 14Neuron 1 in the monkey’s MST responds to an expanding stimulus but not a stimulus with circular movement. Neuron 2 responds to circular movement but not to expansion.ch 7 15Skilled Actions•Skilled actions partly arise from establishing a coordination between sensory and motor systems.•E.g., Somersaulting–Bardy and Laurent found that expert gymnasts performed worse with their eyes closed•They use vision to correct their trajectory•Novice gymnasts do not show this effectch 7 16Physiological Links Between Sensory and Motor Functions•Optic ataxia –Patients suffering from this syndrome produce inaccurate reaching movements towards a target or object in space.•Optic ataxia (3 min)•http://www.youtube.com/watch?v=BkOb9FR5Lgkch 7 17ch 7 18Experiment by Schindler et al.•Participants:2 groups•Patients with parietal lobe damage and normal control participants.•Participants performed two tasks•Bisection task - point to position between cylinders•Reaching task - reach between cylinders and touch a gray stripBisection task In each trial, you saw two cylinders that were shifted different positions. You had to point a place exactly midway between the cylinders.ch 7 19Experiment by Schindler et al.Bisection task In each trial, you saw two cylinders that were shifted different positions. You had to point to a place exactly midway between the cylinders.So, for each trial, you had to point different positions.Trial 1Trial 2pointpointch 7 20Experiment by Schindler et al.Reaching task In each trial, you saw two cylinders that were shifted different positions. You had to touch a gray strip that were 20 cm behind the cylinders. So, for each trial, you had to extend your hand to different positions.Trial 1Trial 2touchtouchch 7 21Results•Bisection task–The patients with parietal lobe damage and normal control were equally accurate•Reaching task–The patients kept reaching the same place even though cylinders were shifted in each trial.Trial 1Trial 2touchtouchch 7 22Interpretation•The parietal lobe provides guidance for movement.•This mechanism operates unconsciously.•But the patients with optic ataxia lost this ability.ch 7 23Visual dominant vs. motor dominant neuronsch 7 24Mirror neuronsch 7 25Mirror neurons•Mirror neurons respond to a particular “kind” of action (e.g., grasping) AND observing someone doing the action.The activity of a particular neuron in the premotor area of a monkey.ch 7 26The activity of a particular neuron in the premotor area of a monkey.(a) This neuron responded when the monkey watched the experimenter grasp the peanut.(b) This neuron also responded when the monkey actually grasped the peanut.(c) This neuron did not respond when the monkey watched the experimenter pick up the peanut with a pair of pliers..ch 7 27Mirror neurons•Respond not only when you are doing a particular action.•But also when you watch someone doing it.•This neuron gives you a general characteristic of an action.ch 7 28What are mirror neurons for?•Facilitate learning by imitation.–Language development–Skill learning•Social interaction–Empathy (understanding others or what others think)–Connecting with others•Autism may be caused by the deficiency in mirror neuronsch 7 29•Video clip from NOVA (PBS)–15 min–http://www.pbs.org/wgbh/nova/sciencenow/3204/01.htmlCreating action by activating motor cortex•motor