2 mm across dave williams lab
DESCRIPTION
2 mm across Dave Williams lab. Receptive Field Measurements (Kuffler). Receptive Fields: Center-Surround Organization. Harmonic Spatial Stimuli. M = mean level, a = contrast, f = spatial frequency. Receptive Field MTF. Sign-conserving and inverting synapses in the main retinal cell types. - PowerPoint PPT PresentationTRANSCRIPT
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2 mm acrossDave Williams lab
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Receptive Field Measurements(Kuffler)
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Receptive Fields: Center-
Surround Organization
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Harmonic Spatial Stimuli
M = mean level, a = contrast, f = spatial frequency
( ) (1 sin(2 ))c x M a fx
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Receptive Field MTF
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Sign-conserving
and inverting synapses in
the main retinal cell
types
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Dacey HI HII size differences
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HI mosaic(Dacey)
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Classical Cone Specific Center-
Surround Hypothesis
(Hubel and Wiesel, 1966; Calkins and Sterling, 2001)
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Classical Cone Specific Center-
Surround Hypothesis
(Hubel and Wiesel, 1966; Calkins and Sterling, 2001)
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Anatomy: Midget Cell Surrounds Receive From All Cone Classes
(Calkins and Sterling)
H1 Horizontals receive non-
selective L,M input
Amacrine populations receive non-selective L,M
input
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Hypothesis: Midget Cone Inputs Differ With Eccentricity
Central Peripheral
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Midget Color Opponency Is Strong In Periphery
(Martin, Lee et al., 2001)
lum
rg
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Midget Color Opponency At Various Temporal
Modulation Rates
(Martin, Lee et al.)
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Midget Cell Centers Are
Debated(Martin and Lee et al., 2001, Nature)
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Methods
• In vitro preparation of primate retina: flourescent dye made the parasol, midget, and bistratified cells visible
• Was able to target cell by its distinguishing cell body and spatial density
• Primary advantage of mounting retina on stage of the microscope: were able to find the ganglion cells easily.
• Recordings were taken to show whether midget, parasol, and bistratified cells showed any evidence of S cone input(blue yellow flicker stimuli)
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Results
• Both midget and parasol cells showed no response to S cone isolating stimuli
• The small bistratified cells gave a strong response to S cone isolating stimuli
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Conclusions
• Isoluminant blue yellow modulation elicited a blue on response in bistratified cells
• The physiological differences between M, L, and S cones may reflect the dichotomy between midget cells, parasol cells, and bistratified cells.
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Implications of this experiment
A Neural circuit may give rise to blue yellow color opponency– Reason: the bistratified cell has a distinct morphologyThere might be a synaptic pathway for S cone signals
formed by bistratified cells and blue cone bipolar cells. Reason: dendritic field of the bistratified cell has the same depth as the axon terminals of the blue cone bipolar cells
Other types of ganglion cells might transmit signals from M and L cone opponent cells
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From an evolutionary standpoint
• Trichromatic vision just recently evolved in mammals
• Most mammals have a S cone system.
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Questions to Ponder
• What about the possible existence of a blue off cell?
• What are the advantages of having a blue on pathway?
• Why do you think primates only recently evolved trichromatic vision?
• What further experiments could be conducted to investigate the question of whether we have a specific circuit for blue yellow opponency?
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A Major Retinal Output For S-
cone Signals Is the Mosaic of
Small Bi-stratified
Ganglion Cells (Calkins)
(Calkins and Sterling)
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There Is Highly Specialized S-Cone Circuitry
(Calkins, J. Del Valle, Kouyama and Marshak, 1992)
S-cone bipolars receive exclusively from S-cones and are pre-synaptic to the small bi-stratified retinal ganglion cells
S-cone
Identified using an antibody for the
neuropeptide cholecystokinin
(CCK)
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Small bi-stratified color responses(Dacey)
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S-cone Small Bistratified
(Calkins and Sterling)