Through the eyes of an animal: how animals see
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Transcript of Through the eyes of an animal: how animals see
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Through the eyes of an animal: how animals see
Ishara Mills-Henry, Ph.D.Science of the Eye Program
Saul Nava, Ph.D.Harvard University and Massachusetts
College of Art and Designwww.scienceoftheeye.org
MIT
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Emperor Scorpions (Pandinus imperator)
• Found in the tropical forests and savannas of Africa
• Docile, although can become territorial and cannibalistic
• Nocturnal –hunts for prey at night
• Habitat: under rocks, logs, and other forest debris
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Scorpion Fluorescence• Scorpions fluorescence under
UV light.• Exoskeleton contains
compounds that exhibit flourescence
• Recent studies suggested its for detection and avoidance of the UV light.
• Ability to discriminate between species?
• Mating, navigation, ?)
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What do animals see?
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What do animals see?New world monkey
Monocular vision
Pit eyes
Great night vision
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Digital Camera and the Eye
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Observe parts of camera• Lenses – focuses light onto the sensor• Sensor (e.g. CCD) –pixels (photosensors) capture light (color
and intensity) and convert it to an electrical signal and digital signal
• Image Processing Unit - processes the information, and creates an image (e.g. jpeg)
LENSES
SENSOR
IMAGE PROCESSOR
Convert Electrical signal to Digital
Convert Electrical signal to Digital
StorageStorage
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The Retina
From www.howstuffworks.com
Retina
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Retina
Humans are considered trichromats
Blue, Red, and Green Cone Photorecpetors
Rod photoreceptors – are important for vision in dim light
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Rods – Low light Cones – Color vision
Three Main Parts:a. Outer Segments
b. Cell bodyc. Synaptic terminal
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Visual Responses• Optokinetic Response/Reflex
– Maintain image on retina stable– Innate reflex
• Optomotor Response/Reflex– Locomotive behavior– Hypothesized to play a role in control of speed and direction of
body movement– Innate reflex
• Escape or Avoidance Response– Avert danger– Innate reflex
Ability to test: Colors, Spatial Frequency, and Motion detection
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Observing our eye movements
• Umbrellas• Groups of threeOne person twists an umbrella while the other tries to focus on the umbrella without moving their eyes.The third person can observe. The umbrella should have a pattern or make stripes on a solid
color umbrella with tape
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Eye movements (microsaccades)
http://www.michaelbach.de/ot/mot_eyeJitter/index.html from Pinna B & Spillmann L (2002) A new illusion of floating motion in depth. Perception 31:1501–1502.
Involuntary eye movements – This illusion makes us aware of the small movements our eyes make. Our eyes these movements even if we think we are focusing on an object. This is to prevent the photoreceptors in the retina from desensitizing. If photoreceptors desensitize they will no longer pass the signal to the brain of the object we are seeing. It would reduce the visibility of an object.
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• Drum lined with black and white stripes
• Light source illuminates drum
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Optokinetic Response
Vertebrates exhibit numerous reflex behaviors that are driven by visual stimuli. The OKR response encompasses smooth eye rotations which track moving patterns followed by sharp movements called saccades.
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Optomotor Response
• Zebrafish (http://baierlab.ucsf.edu/omr.html)
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Escape or Avoidance Response
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Phototaxis
• Movement towards or away from light
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Drosophila
Habitat: rotting fruit
Phototaxis
Eight photoreceptors arranged in a pattern
Vision: myopic/poor spatial quality but able to detect movement quicklySmaller lenses captures less light
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Mealworms/Darkling Beetles (tenebrio moliter)
• Over 20,000 species • Larval stages are used as a food
source fish, reptiles, and birds.• Adult darkling beetles – active
both day and night• Habitat: burrows in grain• Eat mostly vegetation – fresh and
decaying
• Spectral response – 520 nm (green) and 334 – 365 nm (UV)
Do they exhibit negative or positive phototaxis? Does the larval stage behavior differ from the adult stage?
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Planaria (Schmidtea mediterranea)
• Flatworms • Usually used to study
regeneration• Habitat: Under rocks in river beds• Eye contains pigment and
photoreceptor cells
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Materials
• Lights (Color changing light bulb with remote) – $8.00 – 24.00 (Amazon.com)– Alternatives: Filters or different color light bulbs– Flashlights
• Light bulb outlets (Home Depot)• Mazes (PVC pipe – Home Depot)
• Animals (Available at Carolina or Pet store)
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More Interesting InformationFlight Simulator for flies?
May yield info for Robot Vision
http://www.youtube.com/watch?v=e5uPr_3SsHA&feature=player_embedded
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What can animals with compound eyes teach us?
Better Cameras and motion detection systems?
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Measuring Responses
• Place electrode on eye
• Light stimulus flashes over the eye
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Responses
Ganglion Cell Spike Recordings
a = Hyperpolarization of photoreceptors
b = On- Bipolar cells depolarization
d = OFF-Bipolar cellsdepolarization