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23 Cards in this Set

  • Front
  • Back
Functions of the retina
1. adjust for changes in light
2. enocdes a retinal image and sends the info to the brain
3.
What is the pathway of light from the eye to brain?
1. photoreceptors absorb light
2. synapse to bipolar cell
3. synapse to ganglion cell
4. synapse ganglion cell axon to brain
Lateral geniculate nucleus
relay center in the brain for visual info from the retina
How does light travel through the eye?
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.
Horizontal cells
interneurons in the retina that help regulate and connect info from multiple photoreceptors.
Amacrine cells
interneurons in the retina that connect ganglion cells and bipolar cells
What is the distribution of RGCS ( Retinal Ganglion Cells) in the eye?
Parasol- 10%
Midget- 8%
Bistratified- 10%
Parasol cells
ganglion cells that have large dendrites and cell bodies
Midget Cells
Ganglion cells that have small dendrites and bodies
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)
Receptive Field
the field of the world that the cell is receiving information from
Hering Ladder
? ( read about this in the book)
Mach Bands
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.
How is contrast defined?
amplitude of the sine wave divided by the mean luminance
Sine Wave Grating Stimuli
these stimuli are used to measure the receptive field properties and visual performance of behavioral tasks usually concerning neural systems ( e.g. vision).
What is the finest thing you can see? (contrast)
50-60 cycles per degree
contrast sensitivity
1 divided by the contrast threshold
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
How do you measure the width of the center of the ganglion cell?
It is equal to it's sine wave.
What is the distribution of cones and ganglion cells in the retina?
With eccentricity ( by degree) the ganglion cells fall off faster than the density of cones, but they are somewhat similar.
Distribution of ganglion cells
dense in the fovea; decrease as they move out from fovea.
Types of REceptive fields in the retina
Midget- 4 types ( Red and Green Cones)
Small Bistratified K cells - 2 types (Blue cones)
Parasol- L or L+ ( No Cones- no color information)
How does the retina adjust for the light level you are in?
- 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)