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23 Cards in this Set
- Front
- Back
Functions of the retina
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1. adjust for changes in light
2. enocdes a retinal image and sends the info to the brain 3. |
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What is the pathway of light from the eye to brain?
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1. photoreceptors absorb light
2. synapse to bipolar cell 3. synapse to ganglion cell 4. synapse ganglion cell axon to brain |
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Lateral geniculate nucleus
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relay center in the brain for visual info from the retina
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How does light travel through the eye?
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From the surface to the eye (towards the back) to the retina to the brain, then the brain signals a visual image and the neural response is sent from the back of the eye towards the surface.
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Horizontal cells
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interneurons in the retina that help regulate and connect info from multiple photoreceptors.
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Amacrine cells
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interneurons in the retina that connect ganglion cells and bipolar cells
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What is the distribution of RGCS ( Retinal Ganglion Cells) in the eye?
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Parasol- 10%
Midget- 8% Bistratified- 10% |
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Parasol cells
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ganglion cells that have large dendrites and cell bodies
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Midget Cells
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Ganglion cells that have small dendrites and bodies
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Kuffler's Experiment
Explanation & conclusion |
- Spots of light were placed on a screen and then neural activity was recorded.
Conclusions: - Neurons generated action potentials accurately even in the absence of light - receptive fields are generally circular - spots of light at certain locations could reduce or increase the response of the cell: (reduction typically on the outer edges, increase usually in the middle) |
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Receptive Field
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the field of the world that the cell is receiving information from
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Hering Ladder
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? ( read about this in the book)
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Mach Bands
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an optical illusion that exaggerates the differences between two slightly different shades of gray that are next to each other. This exemplifies the retinal process of edge enhancing.
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How is contrast defined?
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amplitude of the sine wave divided by the mean luminance
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Sine Wave Grating Stimuli
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these stimuli are used to measure the receptive field properties and visual performance of behavioral tasks usually concerning neural systems ( e.g. vision).
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What is the finest thing you can see? (contrast)
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50-60 cycles per degree
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contrast sensitivity
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1 divided by the contrast threshold
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Receptive field indicators:
+ and - definition |
+ ganglion cell receptive field portion that is excited by light
- part of the ganglion cell receptive field that is suppressed by light |
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How do you measure the width of the center of the ganglion cell?
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It is equal to it's sine wave.
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What is the distribution of cones and ganglion cells in the retina?
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With eccentricity ( by degree) the ganglion cells fall off faster than the density of cones, but they are somewhat similar.
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Distribution of ganglion cells
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dense in the fovea; decrease as they move out from fovea.
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Types of REceptive fields in the retina
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Midget- 4 types ( Red and Green Cones)
Small Bistratified K cells - 2 types (Blue cones) Parasol- L or L+ ( No Cones- no color information) |
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How does the retina adjust for the light level you are in?
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- change in size of pupil
- two photoreceptor systems: cones for high light, rods for low light - photoreceptors adjust sensitivities - other retinal neurons adjust their sensitivities ( bipolar & horizontal) |