A synaptic signature for ON-and OFF-center
parasol ganglion cells of the primate retina
ARTICLE in VISUAL NEUROSCIENCE 31(1):57-84 · MAY 2014 with 17 READS
Impact Factor: 2.21 · DOI: 10.1017/S0952523813000461 · Source: PubMed

1st Joanna D Crook

2nd Orin S Packer

3rd Dennis M Dacey
ABSTRACT
In the primate retina, parasol ganglion cells contribute to the primary visual
pathway via the magnocellular division of the lateral geniculate nucleus, display ON
and OFF concentric receptive field structure, nonlinear spatial summation, and high
achromatic temporal-contrast sensitivity. Parasol cells may be homologous to the
alpha-Y cells of nonprimate mammals where evidence suggests that N-methyl-Daspartate (NMDA) receptor-mediated synaptic excitation as well as glycinergic
disinhibition play critical roles in contrast sensitivity, acting asymmetrically in OFFbut not ON-pathways. Here, light-evoked synaptic currents were recorded in the
macaque monkey retina in vitro to examine the circuitry underlying parasol cell
receptive field properties. Synaptic excitation in both ON and OFF types was
mediated by NMDA as well as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic
acid (AMPA)/kainate glutamate receptors. The NMDA-mediated current-voltage
relationship suggested high Mg2+ affinity such that at physiological potentials,
NMDA receptors contributed ∼20% of the total excitatory conductance evoked by
moderate stimulus contrasts and temporal frequencies. Postsynaptic inhibition in
both ON and OFF cells was dominated by a large glycinergic "crossover"
conductance, with a relatively small contribution from GABAergic feedforward
inhibition. However, crossover inhibition was largely rectified, greatly diminished at
low stimulus contrasts, and did not contribute, via disinhibition, to contrast
sensitivity. In addition, attenuation of GABAergic and glycinergic synaptic inhibition
left center-surround and Y-type receptive field structure and high temporal
sensitivity fundamentally intact and clearly derived from modulation of excitatory
bipolar cell output. Thus, the characteristic spatial and temporal-contrast sensitivity
of the primate parasol cell arises presynaptically and is governed primarily by
modulation of the large AMPA/kainate receptor-mediated excitatory conductance.
Moreover, the negative feedback responsible for the receptive field surround must
derive from a nonGABAergic mechanism.
Effect of Retinopathy of Prematurity (ROP) on
Scotopic Spatial Summation.
ARTICLE in INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE 55(5) · APRIL 2014
with 11 READS
Impact Factor: 3.40 · DOI: 10.1167/iovs.14-14344 · Source: PubMed

1st Ronald M Hansen

2nd Jena L Tavormina

3rd Anne Moskowitz
27.76 · Harvard University

4th Anne B Fulton
ABSTRACT
Purpose:
To evaluate scotopic retinal organization in retinopathy of prematurity (ROP)
through a study of spatial summation.
Methods:
Thresholds for a range of stimulus diameters (0.4°-10°) were measured using a two
alternative, spatial, forced choice psychophysical procedure. The critical diameter
(DCRIT) for complete summation was estimated in subjects with a history of severe
ROP (N = 7) and mild ROP (N = 17). Subjects who were born preterm and never had
ROP (N = 16) and term-born subjects (N = 7) were also tested. The subjects ranged
in age from 9 to 17 (median 13.5) years.
Results:
Critical diameter for complete spatial summation was significantly larger in ROP
subjects than in subjects who never had ROP and in term-born control subjects.
Critical diameter varied significantly with severity of ROP.
Conclusions:
The larger DCRIT values in ROP are consistent with altered organization of the post
receptor retina. This may offer the ROP retina a strategy for achieving noise
reduction and good dark-adapted visual sensitivity.
Area summation of first- and second-order
modulations of luminance
ARTICLE in JOURNAL OF VISION 15(1) · JANUARY 2015 with 9 READS
Impact Factor: 2.39 · DOI: 10.1167/15.1.12 · Source: PubMed

1st Robert J Summers

2nd Daniel H Baker
31.58 · The University of York

3rd Timothy S Meese
34.72 · Aston University
ABSTRACT
To extend our understanding of the early visual hierarchy, we investigated the longrange integration of first- and second-order signals in spatial vision. In our first
experiment we performed a conventional area summation experiment where we
varied the diameter of (a) luminance-modulated (LM) noise and (b) contrastmodulated (CM) noise. Results from the LM condition replicated previous findings
with sine-wave gratings in the absence of noise, consistent with long-range
integration of signal contrast over space. For CM, the summation function was much
shallower than for LM suggesting, at first glance, that the signal integration process
was spatially less extensive than for LM. However, an alternative possibility was that
the high spatial frequency noise carrier for the CM signal was attenuated by
peripheral retina (or cortex), thereby impeding our ability to observe area
summation of CM in the conventional way. To test this, we developed the "Swiss
cheese" stimulus of Meese and Summers (2007) in which signal area can be varied
without changing the stimulus diameter, providing some protection against
inhomogeneity of the retinal field. Using this technique and a two-component
subthreshold summation paradigm we found that (a) CM is spatially integrated over
at least five stimulus cycles (possibly more), (b) spatial integration follows squarelaw signal transduction for both LM and CM and (c) the summing device integrates
over spatially-interdigitated LM and CM signals when they are co-oriented, but not
when cross-oriented. The spatial pooling mechanism that we have identified would
be a good candidate component for a module involved in representing visual
textures, including their spatial extent.
© 2015 ARVO.
Complementary colors theory of color vision:
Physiology, color mixture, color constancy and
color perception
ARTICLE in COLOR RESEARCH & APPLICATION 36(6):394 - 412 · DECEMBER 2011 with
69 READS
Impact Factor: 1.00 · DOI: 10.1002/col.20611

1st Ralph W. Pridmore
ABSTRACT
I describe complementary colors' physiology and functional roles in color vision, in a
three-stage theory (receptor, opponent color, and complementary color stages). 40
specific roles include the complementary structuring of: S and L cones, opponent
single cells, cardinal directions, hue cycle structure, hue constancy, trichromatic
color mixture, additive/subtractive primaries, two unique hues, color mixture space,
uniform hue difference, lightness-, saturation-, and wavelength/hue-discrimination,
spectral sensitivity, chromatic adaptation, metamerism, chromatic induction,
Helson-Judd effect, colored shadows, color rendering, warm-cool colors, brilliance,
color harmony, Aristotle's flight of colors, white-black responsivity, HelmholtzKohlrausch effect, rainbows/halos/glories, dichromatism, spectral-sharpening, and
trimodality of functions (RGB peaks, CMY troughs whose complementarism adapts
functions to illuminant). The 40 specific roles fall into 3 general roles: color mixture,
color constancy, and color perception. Complementarism evidently structures much
of the visual process. Its physiology is evident in complementarism of cones, and
opponent single cells in retina, LGN, and cortex. Genetics show our first cones were
S and L, which are complementary in daylight D65, giving a standard white to aid
chromatic adaptation. M cone later split from L to oppose the nonspectral (red and
purple) hues mixed from S+L. Response curves and wavelength peaks of cones L, S,
and (S+L), M, closely resemble, and lead to, those of opponent-color chromatic
responses y, b, and r, g, a bimodal system whose summation gives spectralsharpened trimodal complementarism (RGB peaks, CMY troughs). Spectral
sharpening demands a post-receptoral, post-opponent-colors location, hence a third
stage. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011
Binocular summation in the peripheral visual
field
ARTICLE in OPHTHALMIC AND PHYSIOLOGICAL OPTICS 17(2) · MARCH 1997
Impact Factor: 2.18 · DOI: 10.1046/j.1475-1313.1997.97807430.x

1st Angela Whitaker

2nd Shahina Pardhan
35.72 · Anglia Ruskin University
ABSTRACT
Purpose: To investigate binocular summation for a light detection task in the central
and peripheral retina along 4 meridians.
Methods: 10 young subjects aged 22-30 years (mean 26 years) with healthy eyes and
normal visual fields participated in the study. A custom-designed program on a
Humphrey Visual Field Analyser measured thresholds at the fovea and at 5°, 10°,
15°, 25°, 40° and 55° along the horizontal meridian, and at 5°, 10°, 15°, 25°, 40°
along the vertical, 45° oblique and 135° oblique meridians. Right and left monocular
fields and binocular fields were measured on each subject using white spot stimuli
(Goldmann sizes I and III). Binocular summation ratios were calculated for each
eccentricity by dividing binocular sensitivity be the better monocular sensitivity.
Results and conclusion: As expected, binocular and monocular sensitivities
decreased with increasing eccentricity. The mean binocular summation ratio at the
fovea was 1.38 for size I stimulus and 1.42 for size III. Binocular summation was
demonstrated in the peripheral retina along all meridians and is of similar
magnitude to foveal binocular summation. ANOVA showed that binocular
summation was significantly higher in the vertical meridian than horizontal
meridian for both size I and III stimuli. There was no significant variation in
binocular summation ratios with eccentricity along any of the 4 meridians
examined.