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Through the eyes of an animal: how animals see

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 Design www.scienceoftheeye.org MIT. Emperor Scorpions ( Pandinus imperator).

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Through the eyes of an animal: how animals see

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  1. 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 Design www.scienceoftheeye.org MIT

  2. 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

  3. 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, ?)

  4. What do animals see?

  5. What do animals see? New world monkey Pit eyes Great night vision Monocular vision

  6. Digital Camera and the Eye

  7. 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) IMAGE PROCESSOR Convert Electrical signal to Digital LENSES Storage SENSOR

  8. Retina The Retina From www.howstuffworks.com

  9. Retina • Humans are considered trichromats • Blue, Red, and Green Cone Photorecpetors • Rod photoreceptors – are important for vision in dim light

  10. Three Main Parts: a. Outer Segments b. Cell body c. Synaptic terminal Rods – Low light Cones – Color vision

  11. 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

  12. Observing our eye movements • Umbrellas • Groups of three One 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

  13. 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.

  14. Behavior Studies: Testing the Visual Response • Drum lined with black and white stripes • Light source illuminates drum

  15. 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.

  16. Optomotor Response • Zebrafish (http://baierlab.ucsf.edu/omr.html)

  17. Escape or Avoidance Response

  18. Phototaxis • Movement towards or away from light

  19. Drosophila Habitat: rotting fruit Phototaxis Eight photoreceptors arranged in a pattern Vision: myopic/poor spatial quality but able to detect movement quickly Smaller lenses captures less light

  20. 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?

  21. Planaria (Schmidtea mediterranea) • Flatworms • Usually used to study regeneration • Habitat: Under rocks in river beds • Eye contains pigment and photoreceptor cells

  22. 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)

  23. More Interesting Information Flight Simulator for flies? http://www.youtube.com/watch?v=e5uPr_3SsHA&feature=player_embedded May yield info for Robot Vision

  24. What can animals with compound eyes teach us? Better Cameras and motion detection systems?

  25. Measuring Responses • Place electrode on eye • Light stimulus flashes over the eye

  26. Responses a = Hyperpolarization of photoreceptors b = On- Bipolar cells depolarization d = OFF-Bipolar cells depolarization Ganglion Cell Spike Recordings

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