Through the Eyes of Animals: Measuring Animal Vision” In talking about the science of the eye and vision in life science and biology classes, many students are intensely interested in animal vision. They often ask, "What do animals see?" Dr. Mills-Henry presented a way to capitalize on that interest by demonstrating a lab on testing animal vision using easy-to-obtain invertebrate model organisms.

1. Through the eyes of an animal:
how animals see
Ishara Mills-Henry, Ph.D.
Science of the Eye Program
www.scienceoftheeye.org
MIT

3. M

7. 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

8. 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, ?)

9. What do animals see?

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

11. Digital Camera and the Eye

12. 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
electrical signal and digital signal Electrical
signal to
LENSES Digital
Storage
SENSOR
• Image Processing Unit - processes the information, and

13. Retina
The Retina
From www.howstuffworks.com

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

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

16. 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

17. 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

18. 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.

19. • Drum lined with black
and white stripes
• Light source
illuminates drum

20. 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.

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

22. Escape or Avoidance Response

23. Phototaxis
• Movement towards or away from light

24. 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

25. 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?

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

27. 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)

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

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

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

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