Receptive Field Mosaics of Parasol and Midget Ganglion Cells in the Primate Retina
Jeff Gauthier, PhD studentComputational Neurobiology, UC-San Diego
E.J. Chichilnisky’s lab,Salk Institute, San Diego, CA
Research Groups
E.J. Chichinlisky
Salk Institute
Greg Field
Jon Shlens
Eric Frechette
Alan Litke
UC-Santa Cruz
Dumitru Petrusca
Sasha Sher
Matthew Grivich
Functional Characterization of Parasols and Midgets
• What is the relationship between receptive field (RF) and dendritic field (DF)?
• How does coverage of parasols and midgets differ?
• Are the ON-OFF asymmetries of parasols also found in midgets?
Multielectrode Array Recording
Ganglion cell spikes are recorded with an array of 512 extracellular electrodes.
Array designed and built by Alan Litke’s group, UC-Santa Cruz.
Example STAs
OFF ON
par
aso
lm
idge
t
time before spike (msec)
spatial component temporal component
con
tra
st
Stimulus
Example STA
In order to compare many cells, each STA is parameterized by fitting a model.
RFs of all cells
Classification
Functional Characterization of Parasols and Midgets
Are the ON-OFF asymmetries of parasols also found in midgets?
What is the relationship between RF and DF?
How does the coverage of parasol and midget RFs differ?
Parasols have more DF overlap than midgets
Parasol Dendritescoverage of ~3-4
Midget Dendritescoverage of 1
Does DF coverage predict RF coverage? Is RF coverage different for parasols and midgets?
Dacey & Brace (1992), Dacey (1993)
Parasol and midget RFs seem to have the same coverage
What is the relationship between DF and RF?
Mapping RF onto DF
Horizontal bars indicate eccentricity measurement error.Vertical bars indicate s.d. of RF diameter within one retina.DF diameters from Watanabe & Rodieck 1989.
eccentricity (mm, temp. eq.)
dia
met
er (
um
)
Parasol and midget RF diameters taken from5,643 cells in 18 preparations.
Interpretation
By what mechanism are parasol RFs relatively shrunk?– More inhibition on parasol’s peripheral dendrites (Grunert 1999).– Bipolars feeding parasols pool from relatively smaller area.– More attenuation of distal inputs?
Functional Characterization of Parasols and Midgets
Are the ON-OFF asymmetries of parasols also found in midgets?
What is the relationship between RF and DF?
How does the coverage of parasol and midget RFs differ?
different for each
Parasol & midget mosaics
Parasol & midget mosaics
Is coverage really the same?a parametric test
normalized nearest neighbor distance:distance from center to center divided by cell size
Is coverage really the same?a non-parametric test
Is coverage really the same?a non-parametric test
threshold relative to peak
# pixels covered by exactly 1 cell
Interpretation
Higher parasol DF coverage and shrunken RF perfectly compensate to give same coverage as midget, suggesting this coverage factor is the “aim” of development.
Functional Characterization of Parasols and Midgets
Are the ON-OFF asymmetries of parasols also found in midgets?
What is the relationship between RF and DF?
How does the coverage of parasol and midget RFs differ?
same
different for each
ON-OFF Asymmetries
RF diameter (um) time to peak response (msec)
Data taken from 5643 cells from 18 retinas.Bars indicate standard deviation within one retina.
Interpretation
Similarity of ON and OFF asymmetries for parasol and midgets suggest they arise prior to ganglion cell processing
Functional Characterization of Parasols and Midgets
Are the ON-OFF asymmetries of parasols also found in midgets?
What is the relationship between RF and DF?
How does the coverage of parasol and midget RFs differ?
same
yes size speed
different for each
Control for pixel size
time to peak response (msec)size (um)
Parasol-Midget relationship
Functional Characterization of Parasols and Midgets
• Parasol dendrites have much more overlap than midget dendrites. Does dendritic field (DF) overlap predict receptive field (RF) overlap?
• What is the relationship between RF and DF size in parasols? Is it the same for midgets?
• Parasols have ON-OFF asymmetries: ON-parasols are larger and faster and OFF-parasols. Do the same asymmetries hold for ON- and OFF-midgets?
Conclusions
• Relationship between RF and DF is different for parasols and midgets
• Parasols and midgets have same RF coverage • Parasols and midgets have same ON-OFF asymmetries
