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)• 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
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, ?)
Observe parts of camera• Lenses – focuses light onto the sensor IMAGE PROCESSOR• Sensor (e.g. CCD) –pixels (photosensors) capture light (color and intensity) and convert it to an Convert Convert electrical signal and digital signal Electrical Electrical signal to signal to LENSES Digital Digital Storage Storage SENSOR• Image Processing Unit - processes the information, and
Retina Humans are considered trichromats Blue, Red, and Green Cone Photorecpetors Rod photoreceptors – are important for vision in dim light
Three Main Parts: a. Outer Segments b. Cell body c. Synaptic terminalRods – Low lightCones – Color vision
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 reflexAbility to test: Colors, Spatial Frequency, and Motion detection
Observing our eye movements• Umbrellas• Groups of threeOne person twists an umbrellawhile the other tries to focus onthe umbrella without movingtheir eyes.The third person can observe.The umbrella should have a pattern or make stripes on a solid color umbrella with tape
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 eyesthese movements even if we think we are focusing on an object. This is to prevent the photoreceptors in theretina from desensitizing. If photoreceptors desensitize they will no longer pass the signal to the brain of theobject we are seeing. It would reduce the visibility of an object.
• Drum lined with blackand white stripes• Light sourceilluminates drum
Optokinetic ResponseVertebrates exhibit numerous reflex behaviors that are driven by visual stimuli. TheOKR response encompasses smooth eye rotations which track moving patterns followedby sharp movements called saccades.
Phototaxis• Movement towards or away from light
DrosophilaHabitat: rotting fruitPhototaxisEight photoreceptors arranged in a patternVision: myopic/poor spatial quality but ableto detect movement quicklySmaller lenses captures less light
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?
Planaria (Schmidtea mediterranea)• Flatworms• Usually used to study regeneration• Habitat: Under rocks in river beds• Eye contains pigment and photoreceptor cells
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)
More Interesting Information Flight Simulator for flies? http://www.youtube.com/watch?v=e5uPr_3SsHA&feature=player_embedded May yield info for Robot Vision
What can animals with compound eyes teach us?Better Cameras and motiondetection systems?
Measuring Responses• Place electrode on eye• Light stimulus flashesover the eye