1
|
Song J, Breitmeyer BG, Brown JM. Further Examination of the Pulsed- and Steady-Pedestal Paradigms under Hypothetical Parvocellular- and Magnocellular-Biased Conditions. Vision (Basel) 2024; 8:28. [PMID: 38804349 PMCID: PMC11130818 DOI: 10.3390/vision8020028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/12/2024] [Accepted: 04/25/2024] [Indexed: 05/29/2024] Open
Abstract
The pulsed- and steady-pedestal paradigms were designed to track increment thresholds (ΔC) as a function of pedestal contrast (C) for the parvocellular (P) and magnocellular (M) systems, respectively. These paradigms produce contrasting results: linear relationships between ΔC and C are observed in the pulsed-pedestal paradigm, indicative of the P system's processing, while the steady-pedestal paradigm reveals nonlinear functions, characteristic of the M system's response. However, we recently found the P model fits better than the M model for both paradigms, using Gabor stimuli biased towards the M or P systems based on their sensitivity to color and spatial frequency. Here, we used two-square pedestals under green vs. red light in the lower-left vs. upper-right visual fields to bias processing towards the M vs. P system, respectively. Based on our previous findings, we predicted the following: (1) steeper ΔC vs. C functions with the pulsed than the steady pedestal due to different task demands; (2) lower ΔCs in the upper-right vs. lower-left quadrant due to its bias towards P-system processing there; (3) no effect of color, since both paradigms track the P-system; and, most importantly (4) contrast gain should not be higher for the steady than for the pulsed pedestal. In general, our predictions were confirmed, replicating our previous findings and providing further evidence questioning the general validity of using the pulsed- and steady-pedestal paradigms to differentiate the P and M systems.
Collapse
Affiliation(s)
- Jaeseon Song
- Department of Psychology, University of Georgia, Athens, GA 30602, USA;
| | | | - James M. Brown
- Department of Psychology, University of Georgia, Athens, GA 30602, USA;
| |
Collapse
|
2
|
McAnany JJ, Park JC, Fishman GA, Hyde RA. Spatial and Temporal Integration Abnormalities in X-Linked Retinoschisis. Invest Ophthalmol Vis Sci 2022; 63:22. [PMID: 35984651 PMCID: PMC9419457 DOI: 10.1167/iovs.63.9.22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To evaluate spatial and temporal integration across the visual field in individuals with juvenile X-linked retinoschisis (XLRS). Methods Nine subjects with XLRS and 10 visually normal individuals participated. Luminance thresholds were measured at 15 locations along the horizontal visual field meridian. Locations were grouped into four regions for analysis: foveal, parafoveal (2°), perifoveal (5°-10°), and peripheral (10°-60°). For spatial integration measurements, stimulus duration was 100 ms, and size ranged from 0.01 to 2.32 deg2 (Goldmann I-V). For temporal integration measurements, stimulus size was 0.15 deg2 (Goldmann III), and duration ranged from 12 to 800 ms. The effect of stimulus size and duration on the subjects' threshold was described using integration models. Results Luminance thresholds for the XLRS group were more elevated for small targets (2.0×-12.6×) than for large targets (1.25×-3.2×) compared to controls for all locations. Likewise, thresholds for the XLRS group were more elevated for short durations (6.3×) than for long durations (4.0×) in the fovea and parafovea but were similarly elevated at all durations (2.0×-2.5×) in the perifovea and periphery. For both the size and duration experiments, thresholds measured in the fovea, parafovea, and perifovea of XLRS subjects were highly similar to those measured from the peripheral field of the controls. Conclusions Spatial and temporal integration characteristics of the XLRS fovea, parafovea, and perifovea are similar to those of the normal periphery. The results also indicate that scaling stimulus size equates thresholds for the XLRS and control subjects throughout the visual field, but scaling duration does not.
Collapse
Affiliation(s)
- J Jason McAnany
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.,Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Jason C Park
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Gerald A Fishman
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.,The Pangere Center for Inherited Retinal Diseases, The Chicago Lighthouse, Chicago, Illinois, United States
| | - Robert A Hyde
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| |
Collapse
|
3
|
Lee BB, Swanson WH. Detection and discrimination of achromatic contrast: A ganglion cell perspective. J Vis 2022; 22:11. [PMID: 35848903 PMCID: PMC9308016 DOI: 10.1167/jov.22.8.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The magnocellular (MC) pathway in the primate has much higher achromatic contrast sensitivity than the parvocellular (PC) pathway, and is implicated in luminance contrast detection. But MC pathway responses tend to saturate at lower achromatic contrast than do PC pathway responses. It has been proposed that the PC pathway plays a major role in discriminating suprathreshold achromatic contrast, because the MC pathway is in saturation. This has been termed the pulsed-pedestal protocol. To test this hypothesis, responses of MC and PC pathway ganglion cells have been examined under suprathreshold conditions with stimulus configurations similar to those in psychophysical tests. For MC cells, response saturation was much less for flashed or moving edges than for sinusoidal modulation, and MC cell thresholds predicted for these stimuli were similar to psychophysical discrimination (and detection) data. Results suggest the protocol is not effective in segregating MC and PC function.
Collapse
Affiliation(s)
- Barry B Lee
- Graduate Center for Vision Research, Department of Biological Sciences, SUNY College of Optometry, New York, NY, USA.,Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,
| | | |
Collapse
|
4
|
Fernandes Costa M, Dutra Henriques L, Côrrea Pinho O. Development of a Spatio-temporal Contrast Sensitivity Test for Clinical Use. J Ophthalmic Vis Res 2022; 17:69-77. [PMID: 35194498 PMCID: PMC8850854 DOI: 10.18502/jovr.v17i1.10172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 03/11/2021] [Indexed: 11/24/2022] Open
Abstract
Purpose We developed a contrast sensitivity test that considers an integrative approach of spatial and temporal frequencies to evaluate the psychophysical channels in processing two-dimensional stimulus for clinical use. Our new procedure provides a more efficient isolation of the magnocellular and parvocellular visual pathways supporting spatiotemporal contrast sensitivity processing. Methods We evaluated 36 participants of both sexes aged 18–30 years with 20/20 or better best-corrected visual acuity. Two spatial frequencies (0.5 cycles per degree [cpd] and 10 cpd), being in one of the three temporal frequencies (0.5 cycle per second [cps], 7.5 cps, and 15 cps), were presented in a high-resolution gamma corrected monitor. A two-alternative forced-choice procedure was conducted, and the staircase method was used to calculate the contrast sensitivity. Reliability was assessed using a retest procedure within a month (±5 days) under the same conditions. Results Results showed statistical significance in 0.5 cpd and 10 cpd spatial frequencies for 0.5 cps (F = 77.36; p< 0.001), 7.5 cps (F = 778.37; p< 0.001), and 15 cps (F = 827.23; p < 0.001) with a very high (η² = 0.89) effect size. No statistical differences were found between the first and second sessions for all spatial frequencies. For reliability, a significantly high correlation and high internal consistency were found in all spatiotemporal conditions. The limits were calculated for normality. Conclusion We developed an approach to investigate the spatiotemporal integration of contrast sensitivity designed for clinical purposes. The relative contribution of the low spatial frequencies/high temporal frequencies and the high spatial frequencies/low temporal frequencies of the psychophysical channels can also be evaluated separately.
Collapse
Affiliation(s)
- Marcelo Fernandes Costa
- Laboratório da Visão, Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, São Paulo, Brazil.,Núcleo de Neurociências Aplicada, Universidade de São Paulo, São Paulo, Brazil
| | - Leonardo Dutra Henriques
- Laboratório da Visão, Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, São Paulo, Brazil
| | - Otávio Côrrea Pinho
- Laboratório da Visão, Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, São Paulo, Brazil
| |
Collapse
|
5
|
Brooks CJ, Chan YM, Fielding J, White OB, Badcock DR, McKendrick AM. Visual contrast perception in visual snow syndrome reveals abnormal neural gain but not neural noise. Brain 2021; 145:1486-1498. [PMID: 34633444 DOI: 10.1093/brain/awab383] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 09/17/2021] [Accepted: 09/21/2021] [Indexed: 11/14/2022] Open
Abstract
Visual snow syndrome is a neurological condition characterised by a persistent visual disturbance, visual snow, in conjunction with additional visual symptoms. Cortical hyperexcitability is a potential pathophysiological mechanism, which could be explained by increased gain in neural responses to visual input. Alternatively, neural noise in the visual pathway could be abnormally elevated. We assessed these two potential competing neural mechanisms in our studies of visual contrast perception. Cortical hyperexcitation also occurs in migraine, which commonly co-occurs with visual snow syndrome. Therefore, to determine whether the effect of visual snow syndrome can be distinguished from interictal migraine, we recruited four participant groups: controls, migraine alone, visual snow syndrome alone, visual snow syndrome with migraine. In the first experiment, we estimated internal noise in 20 controls, 21 migraine participants, 32 visual snow syndrome participants (16 with migraine) using a luminance increment detection task. In the second experiment, we estimated neural contrast gain in 21 controls, 22 migraine participants, 35 visual snow syndrome participants (16 with migraine) using tasks assessing sensitivity to changes in contrast from a reference. Contrast gain and sensitivity were measured for the putative parvocellular and ON and OFF magnocellular pathways, respectively. We found that luminance increment thresholds and internal noise estimates were normal in both visual snow syndrome and migraine. Contrast gain measures for putative parvocellular processing and contrast sensitivity for putative OFF magnocellular processing were abnormally increased in visual snow syndrome, regardless of migraine status. Therefore, our results indicate that visual snow syndrome is characterised by increased neural contrast gain but not abnormal neural noise within the targeted pathways.
Collapse
Affiliation(s)
- Cassandra J Brooks
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Australia
| | - Yu Man Chan
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Australia
| | - Joanne Fielding
- Department of Neurosciences, Central Clinical School, Monash University, Melbourne, Australia
| | - Owen B White
- Department of Neurosciences, Central Clinical School, Monash University, Melbourne, Australia
| | - David R Badcock
- School of Psychological Science, The University of Western Australia, Crawley, Western Australia
| | - Allison M McKendrick
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Australia
| |
Collapse
|
6
|
Abstract
We as a couple spent 50 years working in visual psychophysics of color vision, temporal vision, and luminance adaptation. We sought collaborations with ophthalmologists, anatomists, physiologists, physicists, and psychologists, aiming to relate visual psychophysics to the underlying physiology of the primate retina. This review describes our journey and reflections in exploring the visual system.
Collapse
Affiliation(s)
- Joel Pokorny
- Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois 60637, USA;,
| | - Vivianne C. Smith
- Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois 60637, USA;,
| |
Collapse
|
7
|
Tuten WS, Cooper RF, Tiruveedhula P, Dubra A, Roorda A, Cottaris NP, Brainard DH, Morgan JIW. Spatial summation in the human fovea: Do normal optical aberrations and fixational eye movements have an effect? J Vis 2018; 18:6. [PMID: 30105385 PMCID: PMC6091889 DOI: 10.1167/18.8.6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Psychophysical inferences about the neural mechanisms supporting spatial vision can be undermined by uncertainties introduced by optical aberrations and fixational eye movements, particularly in fovea where the neuronal grain of the visual system is fine. We examined the effect of these preneural factors on photopic spatial summation in the human fovea using a custom adaptive optics scanning light ophthalmoscope that provided control over optical aberrations and retinal stimulus motion. Consistent with previous results, Ricco's area of complete summation encompassed multiple photoreceptors when measured with ordinary amounts of ocular aberrations and retinal stimulus motion. When both factors were minimized experimentally, summation areas were essentially unchanged, suggesting that foveal spatial summation is limited by postreceptoral neural pooling. We compared our behavioral data to predictions generated with a physiologically-inspired front-end model of the visual system, and were able to capture the shape of the summation curves obtained with and without pre-retinal factors using a single postreceptoral summing filter of fixed spatial extent. Given our data and modeling, neurons in the magnocellular visual pathway, such as parasol ganglion cells, provide a candidate neural correlate of Ricco's area in the central fovea.
Collapse
Affiliation(s)
- William S Tuten
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA.,Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, USA
| | - Robert F Cooper
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA.,Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, USA
| | - Pavan Tiruveedhula
- School of Optometry and Vision Science Graduate Group, University of California, Berkeley, Berkeley, CA, USA
| | - Alfredo Dubra
- Department of Ophthalmology, Stanford University, Stanford, CA, USA
| | - Austin Roorda
- School of Optometry and Vision Science Graduate Group, University of California, Berkeley, Berkeley, CA, USA
| | - Nicolas P Cottaris
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA
| | - David H Brainard
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA
| | - Jessica I W Morgan
- Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, USA.,Center for Advanced Retinal and Ocular Therapeutics, University of Pennsylvania, Philadelphia, PA, USA
| |
Collapse
|
8
|
Differential effects of transient attention on inferred parvocellular and magnocellular processing. Vision Res 2012; 74:21-9. [DOI: 10.1016/j.visres.2012.06.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Revised: 06/10/2012] [Accepted: 06/12/2012] [Indexed: 11/19/2022]
|
9
|
Cao D, Zele AJ, Pokorny J, Lee DY, Messner LV, Diehl C, Ksiazek S. Functional loss in the magnocellular and parvocellular pathways in patients with optic neuritis. Invest Ophthalmol Vis Sci 2011; 52:8900-7. [PMID: 22016061 DOI: 10.1167/iovs.11-7644] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To evaluate contrast threshold and contrast gain in patients with optic neuritis under conditions designed to favor mediation by either the inferred magnocellular (MC) or parvocellular (PC) pathway. METHODS Achromatic and chromatic contrast discrimination was measured in 11 patients with unilateral or bilateral optic neuritis and in 18 age-matched controls with normal vision, using achromatic steady- and pulsed-pedestal paradigms to bias performance toward the MC or PC pathway, respectively. In addition, L-M chromatic discrimination at equiluminance was evaluated using the steady-pedestal paradigm. A physiologically plausible model could describe the data with parameters accounting for contrast gain and contrast sensitivity in the inferred MC or PC pathway. The fitted parameters from the eye affected by optic neuritis were compared with those from the normal eye using generalized estimation equation (GEE) models that can account for within-subject correlations. RESULTS Compared with normal eyes, the affected eyes had significantly higher saturation parameters when measured with both the achromatic pulsed-pedestal paradigm (GEE: β [SE] = 0.35 [0.06]; P < 0.001) and the chromatic discrimination paradigm (β [SE] = 0.18 [0.08]; P = 0.015), suggesting that contrast gain in the inferred PC pathway is reduced; the affected eyes also had reduced absolute sensitivity in the inferred MC pathway measured with the achromatic steady-pedestal paradigm (β [SE] = 0.12 [0.04]; P = 0.005). CONCLUSIONS Optic neuritis produced large sensitivity losses mediated by the MC pathway and contrast gain losses in the inferred PC pathway. A clinical framework is presented for interpreting contrast sensitivity and gain loss to chromatic and achromatic stimuli in terms of retinal and postretinogeniculate loci contributions to detection and discrimination.
Collapse
Affiliation(s)
- Dingcai Cao
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1905 W.Taylor Street, Room 149, Chicago, IL 60615, USA.
| | | | | | | | | | | | | |
Collapse
|
10
|
Elliott SL, Werner JS. Age-related changes in contrast gain related to the M and P pathways. J Vis 2010; 10:4.1-15. [PMID: 20465324 PMCID: PMC2872115 DOI: 10.1167/10.4.4] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 02/13/2010] [Indexed: 11/24/2022] Open
Abstract
Neural contributions to the age-related reduction in spatial vision are incontrovertible. Whether there are differential age-related changes in the magnocellular (M) and parvocellular (P) pathways across the life span has not been tested extensively. We studied psychophysically the contrast gain signature of the M and P pathways for 13 younger and 13 older observers. Two separate paradigms thought to separate the M and P pathways based on their contrast gain (J. Pokorny & V. C. Smith, 1997) signature were used. A four-square array was presented as an increment or decrement on a background of 115 Td for 35 ms, with one test square presented at a slightly higher or lower retinal illumination. Using a four-alternative forced-choice procedure, the observer's task was to choose the unique square. The two paradigms differed only in the pretrial adaptation and inter-stimulus array. Data were fitted with models of contrast discrimination derived from the unique contrast gain signatures. The fitted models indicate a change in the discrimination functions with age for both the M and P pathways, revealing a shift in the contrast gain slope. Results indicate that both M and P pathways undergo age-related changes, but functional losses appear greater for the P pathway under the conditions tested.
Collapse
Affiliation(s)
- Sarah L Elliott
- Department of Ophthalmology & Vision Science, University of California-Davis, 4860 Y Street, Sacramento, CA 95817, USA.
| | | |
Collapse
|
11
|
Magnocellular and parvocellular pathway mediated luminance contrast discrimination in amblyopia. Vision Res 2010; 50:969-76. [PMID: 20211198 DOI: 10.1016/j.visres.2010.03.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 03/02/2010] [Accepted: 03/02/2010] [Indexed: 11/21/2022]
Abstract
To evaluate whether luminance contrast discrimination losses in amblyopia on putative magnocellular (MC) and parvocellular (PC) pathway tasks reflect deficits at retinogeniculate or cortical sites. Fifteen amblyopes including six anisometropes, seven strabismics, two mixed and 12 age-matched controls were investigated. Contrast discrimination was measured using established psychophysical procedures that differentiate MC and PC processing. Data were described with a model of the contrast response of primate retinal ganglion cells. All amblyopes and controls displayed the same contrast signatures on the MC and PC tasks, with three strabismics having reduced sensitivity. Amblyopic PC contrast gain was similar to electrophysiological estimates from visually normal, non-human primates. Sensitivity losses evident in a subset of the amblyopes reflect cortical summation deficits, with no change in retinogeniculate contrast responses. The data do not support the proposal that amblyopic contrast sensitivity losses on MC and PC tasks reflect retinogeniculate deficits, but rather are due to anomalous post-retinogeniculate cortical processing of retinal signals.
Collapse
|
12
|
Sun H, Swanson WH, Arvidson B, Dul MW. Assessment of contrast gain signature in inferred magnocellular and parvocellular pathways in patients with glaucoma. Vision Res 2008; 48:2633-41. [PMID: 18501947 DOI: 10.1016/j.visres.2008.04.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 04/04/2008] [Accepted: 04/10/2008] [Indexed: 10/22/2022]
Abstract
PURPOSE Contrast gain signatures of inferred magnocellular and parvocellular postreceptoral pathways were assessed for patients with glaucoma using a contrast discrimination paradigm developed by Pokorny and Smith. The potential causes for changes in contrast gain signature were investigated using model simulations of ganglion cell contrast responses. METHODS Foveal contrast discrimination thresholds were measured with a pedestal-Delta-pedestal paradigm developed by Pokorny and Smith [Pokorny, J., & Smith, V. C. (1997). Psychophysical signatures associated with magnocellular and parvocellular pathway contrast gain. Journal of the Optical Society of America A, 14(9), 2477-2486]. Stimuli were 27 ms luminance increments superimposed on 227 ms pulsed Delta-pedestals. Contrast thresholds and contrast gain signatures mediated by the inferred magnocellular (MC) and parvocellular (PC) pathways were assessed using linear fits to contrast discrimination thresholds at either lower or higher Delta-pedestal contrasts, respectively. Twenty-seven patients with glaucoma were tested, as well as 16 age-similar control subjects free of eye disease. RESULTS Contrast sensitivity and contrast gain signature mediated by the inferred MC pathway were lower for the glaucoma group, and reduced contrast gain signature was correlated with reduced contrast sensitivity (r(2)=45%, p<.0005). These two parameters mediated by the inferred PC pathway were little affected for the glaucoma group. Model simulations suggest that the reduced contrast sensitivity and contrast gain signature were consistent with the hypothesis that reduced MC ganglion cell dendritic complexity can lead to reduced effective retinal illuminance, and hence increased semi-saturation contrast of the ganglion cell contrast response functions. CONCLUSIONS The contrast sensitivity and contrast gain signature of the inferred MC pathway were reduced in patients with glaucoma. The results were consistent with a model of ganglion cell dysfunction due to reduced synaptic density.
Collapse
Affiliation(s)
- Hao Sun
- Buskerud University College, Department of Optometry & Visual Sciences, Frogsvei 41, P.O. Box 251, 3603 Kongsberg, Norway.
| | | | | | | |
Collapse
|
13
|
McAnany JJ, Levine MW. Magnocellular and parvocellular visual pathway contributions to visual field anisotropies. Vision Res 2007; 47:2327-36. [PMID: 17662333 DOI: 10.1016/j.visres.2007.05.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Revised: 05/22/2007] [Accepted: 05/23/2007] [Indexed: 11/21/2022]
Abstract
It is well established that sensitivity is not necessarily equivalent at isoeccentric locations across the visual field. The focus of this study was a psychophysical examination of the spatial sensitivity differences between the upper and lower visual hemifields under conditions biased toward the presumed magnocellular or parvocellular visual pathway. Experiment 1 showed higher contrast sensitivity in the lower visual field when visual sensitivity was biased toward the parvocellular pathway; no visual field anisotropy was found when sensitivity was biased toward the magnocellular pathway. Experiment 2 showed that the magnitude of the contrast sensitivity anisotropy within the presumed parvocellular pathway increased when test targets of higher spatial frequency were used. The results of this study have relevance for the design both of psychophysical paradigms and clinical training programs for patients with heterogeneous visual field loss.
Collapse
Affiliation(s)
- J Jason McAnany
- Department of Psychology and Laboratory of Integrative Neuroscience, The University of Illinois at Chicago, M/C 285, 1007 West Harrison Street, Chicago, IL 60607-7137, USA.
| | | |
Collapse
|
14
|
Lutze M, Pokorny J, Smith VC. Achromatic parvocellular contrast gain in normal and color defective observers: Implications for the evolution of color vision. Vis Neurosci 2006; 23:611-6. [PMID: 16962004 DOI: 10.1017/s0952523806233078] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Accepted: 11/22/2005] [Indexed: 11/07/2022]
Abstract
The PC pathway conveys both chromatic and achromatic information, with PC neurons being more responsive to chromatic (L−M) than to achromatic (L+M) stimuli. In considering the evolution of color vision, it has been suggested that the dynamic range of chromatic PC-pathway processing is tuned to the chromatic content of the natural environment. Anomalous trichromats, with reduced separation of their L- and M-cone spectral sensitivities, have diminished chromatic input to PC-pathway cells. Dichromats, with absent L or M cones, should have no chromatic input to PC-pathway cells. Therefore, the PC-pathway dynamic range of color defectives should be released from any constraint imposed by the chromatic environment. Here we ask whether this results in compensatory enhancement of achromatic PC-pathway processing in color defectives. This study employed a psychophysical method designed to isolate PC-pathway processing using achromatic stimuli. In a pulsed-pedestal condition, a four-square stimulus array appeared within a uniform surround. During a trial, one of the test squares differed from the other three, and the observer's task was to choose the square that was different. A four-alternative, forced-choice method was used to determine thresholds as a function of the contrast of the four-square array to the surround. Seven color defective and four normal observers participated. Results showed no systematic differences between normals and color defectives. There was no enhancement of achromatic processing as compensation for reduced chromatic processing in the PC-pathway system in color defectives. From physiological recordings, PC-pathway achromatic contrast gains of dichromatic and trichromatic New World primates and trichromatic Old World macaques have also been shown to be similar to each other. Our study and the animal studies imply that PC-pathway contrast gain parameters were regulated by factors other than the environmental chromaticity gamut, and may have arisen in a nontrichromatic common ancestor to both Old and New World primates.
Collapse
Affiliation(s)
- Margaret Lutze
- Department of Ophthalmology and Visual Science, The University of Chicago, Chicago, Illinois 60637, USA
| | | | | |
Collapse
|
15
|
Alexander KR, Barnes CS, Fishman GA. Characteristics of contrast processing deficits in X-linked retinoschisis. Vision Res 2005; 45:2095-107. [PMID: 15845241 DOI: 10.1016/j.visres.2005.01.037] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Revised: 01/17/2005] [Accepted: 01/19/2005] [Indexed: 11/30/2022]
Abstract
Contrast sensitivity and contrast discrimination were evaluated in six males with X-linked retinoschisis (XLRS), a form of early-onset macular degeneration, using testing paradigms designed to favor either the magnocellular (MC) or parvocellular (PC) pathway. Compared to a group of age-similar control observers, the patients with XLRS showed a pronounced loss of contrast sensitivity at high spatial frequencies, consistent with their reduced visual acuities. At low spatial frequencies, the patients' deficits were greater under conditions favoring the MC pathway, for both contrast sensitivity and contrast discrimination. The pattern of contrast sensitivity loss shown by the patients with XLRS could be simulated in control observers by testing at a parafoveal locus, although by optical coherence tomography, none of the patients with XLRS had eccentric fixation. The pattern of findings indicates that the foveas of patients with XLRS functionally resemble the normal parafoveal retina.
Collapse
Affiliation(s)
- Kenneth R Alexander
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 60612, USA.
| | | | | |
Collapse
|
16
|
Abstract
The Zoellner illusion is a geometric distortion occurring when
nonorthogonal inducing lines appear to tilt veridically parallel bars.
The retinal pathways contributing to such illusions are unknown. The
goal of this experiment was to investigate the retinal origin of the
illusion. This was accomplished by determining the contrast gain for
illusion thresholds. The magnocellular (MC-) and parvocellular (PC-)
pathways exhibit different contrast gains, and this difference can be
used psychophysically to identify the pathway. The stimulus pattern was
four vertical bars with a series of inducing lines. The bars were
always 5% higher in contrast than the inducing bars. The pattern was
presented on a larger pedestal. Two paradigms were used. In the
pulsed-pedestal paradigm, the observer adapted to the background and
the pedestal and pattern were presented together as a brief pulse. In
the steady-pedestal paradigm, the observer adapted to the continuously
presented pedestal and the pattern appeared as a brief pulse. The
contrast between the pedestal and the pattern was varied to obtain
thresholds for two criteria: perceiving the directions of the inner
inducing lines, and perceiving the distortion of the bars. The results
for both criteria were similar in shape, but displaced in sensitivity.
Detection of the directions of the inner inducing lines was
0.16–0.29 log unit more sensitive than perception of the
illusion. The data for the pulsed-pedestal paradigm depended on the
contrast between the pedestal and the pattern and produced a shallow
V-shape. These results were associated with mediation in the
PC-pathway. The data for the steady-pedestal paradigm depended on the
pedestal luminance in a linear relation and showed similar sensitivity
to the data for the pulsed-pedestal paradigm. Perception of the
illusion required 10–15% Weber contrast.
Collapse
Affiliation(s)
- Marco J H Puts
- Visual Science Laboratories, University of Chicago, Chicago, IL 60637, USA.
| | | | | |
Collapse
|
17
|
Abstract
The goal of this study was to investigate the role of inferred parvocellular (PC) and magnocellular (MC) pathways in spatial contrast sensitivity. Localized, spatially narrow-band patterns (sixth derivatives of Gaussians, D6s) were presented at various peak spatial frequencies. When the D6 appeared on a pulsed luminance pedestal (Pulsed-Pedestal Paradigm), the spatial contrast sensitivity showed a band-pass shape with good contrast sensitivity at medium spatial frequencies. When the D6 appeared on a steady luminance pedestal (Steady-Pedestal Paradigm), the spatial contrast sensitivity showed a low-pass shape with decreased sensitivity at high spatial frequencies. The band-pass CSF was interpreted as reflecting PC-pathway mediation; the lower spatial frequency region of the low-pass CSF as reflecting MC-pathway mediation.
Collapse
Affiliation(s)
- Anna Leonova
- Visual Sciences Center, University of Chicago, 940 East 57th Street, Chicago, IL 60637, USA.
| | | | | |
Collapse
|