Lecture 2 - Light, Eye, and Retina: First Steps in Seeing Flashcards
(lecture):
Visible light is a part of the electromagnetic spectrum that our eye can pick up. (see page 1 on G doc lecture notes for diagram)
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(lecture):
What are 3 different ways light can travel?
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- Light can be absorbed.
- Light can go through a surface but is then refracted (bent)
- Light can be reflected.
- How light is reflected depends on the reflectance and the orientation of surfaces.
- The environmental structure leads to a spatial light pattern of differential spectral composition and intensity.
- As a consequence of the relation between environment and light pattern, organisms can exploit reflected light to gain information about the structure of the environment.
(lecture):
Read the purple section on page 2 of G doc notes
(Light can be picked up in different ways by different animals:)
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(lecture):
Describe the anatomy of the human eye, and how light travels through it.
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see page 2 on G doc notes
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Read the green section on page 3 of G doc notes
(eye and optics)
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Describe the structure of the retina in the human eye
- And explain how light travels through it so that information can then travel to the brain.
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(see page 3 in G doc notes for diagram)
The retina contains lots of cells ordered in a structured fashion.
There are 3 layers of cells in the retina: photoreceptors, interneurons, ganglion cells.
Light comes in from the bottom, travels through lots of cells to reach the photoreceptors.
The photoreceptors pick up that light and change the response rate for picking up light rays.
The photoreceptors then communicate whether or not they have been activated by light to a layer of interneurons. These cells then forward this information to the ganglion cells. The ganglion cells then take that information out of the eye and communicate that to the brain.
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What are the 2 different types of photoreceptors in the human eye called?
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Rods and Cones
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Describe the difference between the 2 types of photoreceptors in the human eye: Rods and Cones.
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see table on page 4 of G doc notes
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Describe, referencing the structure of the retina, why there is a difference in spatial resolution between Rods and Cones.
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(see page 4 of G doc notes)
(Duplex retina: two systems for seeing)
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Who initially discovered the system of Rods and Cones?
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Santiago Ramón y Cajal (Nobel prize 1906)
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Describe the distribution of photoreceptors in the human eye.
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(see page 5 of G doc notes for diagram)
In the centre of your visual field you have almost exclusively cones. When you directly look at something you look at it using the fovea which consists of only your cone system, so it is less sensitive to light but more detailed, and less sensitive to motion.
In your periphery, the density of cones goes down and the density of rods goes up. You use mainly your rod system for this, so it is more sensitive to light and more sensitive to motion.
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Why does the human eye have a blindspot? What is this?
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(see page 5 of G doc notes for diagram)
Where the light information from the ganglion cells leaves the eye through the optic nerve, that is the blind spot as there are no photoreceptors there.
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Who are 2 classic vision researchers?
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not very important info, but see page 6 on G doc notes
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Give the definition of the receptive field.
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Receptive Field: A specific region of sensory space in which an appropriate stimulus leads to a response in a sensory neuron.
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Receptive Field: A specific region of sensory space in which an appropriate stimulus leads to a response in a sensory neuron.
- In this definition, what is meant by a region of sensory space?
- In this definition, what is meant by an appropriate stimulus?
(lecture):
(see page 6 + 7 in G doc notes)
(The receptive field)
