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Kremers J, Huchzermeyer C. Electroretinographic responses to periodic stimuli in primates and the relevance for visual perception and for clinical studies. Vis Neurosci 2024; 41:E004. [PMID: 39523890 PMCID: PMC11579838 DOI: 10.1017/s0952523824000038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 08/01/2024] [Accepted: 08/01/2024] [Indexed: 11/16/2024]
Abstract
Currently, electroretinograms (ERGs) are mainly recorded while using flashes as stimuli. In this review, we will argue that strong flashes are not ideal for studying visual information processing. ERG responses to periodic stimuli may be more strongly associated with the activity of post-receptoral neurons (belonging to different retino-geniculate pathways) and, therefore, be more relevant for visual perception. We will also argue that the use of periodic stimuli may be an attractive addition to clinically available retinal electrophysiological methods.
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Affiliation(s)
- Jan Kremers
- Section for Retinal Physiology, University Hospital Erlangen, Erlangen, Germany
| | - Cord Huchzermeyer
- Section for Retinal Physiology, University Hospital Erlangen, Erlangen, Germany
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Martin JT, Boynton GM, Baker DH, Wade AR, Spitschan M. PySilSub: An open-source Python toolbox for implementing the method of silent substitution in vision and nonvisual photoreception research. J Vis 2023; 23:10. [PMID: 37450287 PMCID: PMC10353748 DOI: 10.1167/jov.23.7.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 06/11/2023] [Indexed: 07/18/2023] Open
Abstract
The normal human retina contains several classes of photosensitive cell-rods for low-light vision, three cone classes for daylight vision, and intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing melanopsin for non-image-forming functions, including pupil control, melatonin suppression, and circadian photoentrainment. The spectral sensitivities of the photoreceptors overlap significantly, which means that most lights will stimulate all photoreceptors to varying degrees. The method of silent substitution is a powerful tool for stimulating individual photoreceptor classes selectively and has found much use in research and clinical settings. The main hardware requirement for silent substitution is a spectrally calibrated light stimulation system with at least as many primaries as there are photoreceptors under consideration. Device settings that will produce lights to selectively stimulate the photoreceptor(s) of interest can be found using a variety of analytic and algorithmic approaches. Here we present PySilSub (https://github.com/PySilentSubstitution/pysilsub), a novel Python package for silent substitution featuring flexible support for individual colorimetric observer models (including human and mouse observers), multiprimary stimulation devices, and solving silent substitution problems with linear algebra and constrained numerical optimization. The toolbox is registered with the Python Package Index and includes example data sets from various multiprimary systems. We hope that PySilSub will facilitate the application of silent substitution in research and clinical settings.
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Affiliation(s)
- Joel T Martin
- Department of Psychology, University of York, York, UK
| | | | - Daniel H Baker
- Department of Psychology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Alex R Wade
- Department of Psychology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Manuel Spitschan
- Max Planck Institute for Biological Cybernetics, Tübingen, Germany
- TUM Department of Sport and Health Sciences (TUM SG), Technical University of Munich, Munich, Germany
- TUM Institute for Advanced Study (TUM-IAS), Technical University of Munich, Garching, Germany
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Abstract
Rods and cones mediate visual perception over 9 log units of light intensities, with both photoreceptor types contributing to a middle 3-log unit range that comprises most night-time conditions. Rod function in this mesopic range has been difficult to isolate and study in vivo because of the paucity of mutants that abolish cone signaling without causing photoreceptor degeneration. Here we describe a novel Gnat2 knockout mouse line (Gnat2−/−) ideal for dissecting rod and cone function. In this line, loss of Gnat2 expression abolished cone phototransduction, yet there was no loss of cones, disruption of the photoreceptor mosaic, nor change in general retinal morphology up to at least 9 months of age. Retinal microglia and Müller glia, which are highly sensitive to neuronal pathophysiology, were distributed normally with morphologies indistinguishable between Gnat2−/− and wildtype adult mice. ERG recordings demonstrated complete loss of cone-driven a-waves in Gnat2−/− mice; comparison to WT controls revealed that rods of both strains continue to function at light intensities exceeding 104 photoisomerizations rod−1 s−1. We conclude that the Gnat2−/− mouse is a preferred model for functional studies of rod pathways in the retina when degeneration could be an experimental confound.
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Abstract
Electroretinography is a crucial assay for studying the function and the functional integrity of the retina. The mouse is an important animal model for studying the retinal neurons and circuitries. In addition, it is often used as animal model for human retinal disorders. Therefore, a good understanding of the procedures in animal handling, of the methods for data analysis and of the requirements for stimulators and for the data acquisition equipment is of importance. Here, the currently most common methods and materials for in vivo electroretinography in the mouse are discussed.
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Affiliation(s)
- Jan Kremers
- Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany.
| | - Naoyuki Tanimoto
- Department of Ophthalmology, University Hospital Schleswig-Holstein, Kiel, Germany
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Aher AJ, McKeefry DJ, Parry NRA, Maguire J, Murray IJ, Tsai TI, Huchzermeyer C, Kremers J. Rod- versus cone-driven ERGs at different stimulus sizes in normal subjects and retinitis pigmentosa patients. Doc Ophthalmol 2017; 136:27-43. [PMID: 29134295 DOI: 10.1007/s10633-017-9619-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 11/02/2017] [Indexed: 10/18/2022]
Abstract
PURPOSE To study how rod- and cone-driven responses depend on stimulus size in normal subjects and patients with retinitis pigmentosa (RP), and to show that comparisons between responses to full-field (FF) and smaller stimuli can be useful in diagnosing and monitoring disorders of the peripheral retina without the need for lengthy dark adaptation periods. METHOD The triple silent substitution technique was used to isolate L-cone-, M-cone- and rod-driven ERGs with 19, 18 and 33% photoreceptor contrasts, respectively, under identical mean luminance conditions. Experiments were conducted on five normal subjects and three RP patients. ERGs on control subjects were recorded at nine different temporal frequencies (between 2 and 60 Hz) for five different stimulus sizes: FF, 70°, 60°, 50° and 40° diameter circular stimuli. Experiments on RP patients involved rod- and L-cone-driven ERG measurements with FF and 40° stimuli at 8 and 48 Hz. Response amplitudes were defined as those of the first harmonic component after Fourier analysis. RESULTS In normal subjects, rod-driven responses displayed a fundamentally different behavior than cone-driven responses, particularly at low temporal frequencies. At low and intermediate temporal frequencies (≤ 12 Hz), rod-driven signals increased by a factor of about four when measured with smaller stimuli. In contrast, L- and M-cone-driven responses in this frequency region did not change substantially with stimulus size. At high temporal frequencies (≥ 24 Hz), both rod- and cone-driven response amplitudes decreased with decreasing stimulus size. Signals obtained from rod-isolating stimuli under these conditions are likely artefactual. Interestingly, in RP patients, both rod-driven and L-cone-driven ERGs were similar using 40° and FF stimuli. CONCLUSION The increased responses with smaller stimuli in normal subjects to rod-isolating stimuli indicate that a fundamentally different mechanism drives the ERGs in comparison with the cone-driven responses. We propose that the increased responses are caused by stray light stimulating the peripheral retina, thereby allowing peripheral rod-driven function to be studied using the triple silent substitution technique at photopic luminances. The method is effective in studying impaired peripheral rod- and cone- function in RP patients.
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Affiliation(s)
- Avinash J Aher
- Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany
| | - Declan J McKeefry
- School of Optometry and Vision Science, University of Bradford, Bradford, UK
| | - Neil R A Parry
- School of Optometry and Vision Science, University of Bradford, Bradford, UK.,Center for Hearing and Vision Research, Institute of Human Development, University of Manchester, Manchester, UK.,Vision Science Center, Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Center, Manchester, UK
| | - John Maguire
- School of Optometry and Vision Science, University of Bradford, Bradford, UK
| | - I J Murray
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - Tina I Tsai
- Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany
| | - Cord Huchzermeyer
- Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany
| | - Jan Kremers
- Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany. .,School of Optometry and Vision Science, University of Bradford, Bradford, UK.
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Zele AJ, Feigl B, Kambhampati PK, Aher A, McKeefry D, Parry N, Maguire J, Murray I, Kremers J. A Temporal White Noise Analysis for Extracting the Impulse Response Function of the Human Electroretinogram. Transl Vis Sci Technol 2017; 6:1. [PMID: 29109907 PMCID: PMC5666911 DOI: 10.1167/tvst.6.6.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 09/23/2017] [Indexed: 12/22/2022] Open
Abstract
PURPOSE We introduce a method for determining the impulse response function (IRF) of the ERG derived from responses to temporal white noise (TWN) stimuli. METHODS This white noise ERG (wnERG) was recorded in participants with normal trichromatic vision to full-field (Ganzfeld) and 39.3° diameter focal stimuli at mesopic and photopic mean luminances and at different TWN contrasts. The IRF was obtained by cross-correlating the TWN stimulus with the wnERG. RESULTS We show that wnERG recordings are highly repeatable, with good signal-to-noise ratio, and do not lead to blink artifacts. The wnERG resembles a flash ERG waveform with an initial negativity (N1) followed by a positivity (P1), with amplitudes that are linearly related to stimulus contrast. These N1 and N1-P1 components showed commonalties in implicit times with the a- and b-waves of flash ERGs. There was a clear transition from rod- to cone-driven wnERGs at ∼1 photopic cd.m-2. We infer that oscillatory potentials found with the flash ERG, but not the wnERG, may reflect retinal nonlinearities due to the compression of energy into a short time period during a stimulus flash. CONCLUSION The wnERG provides a new approach to study the physiology of the retina using a stimulation method with adaptation and contrast conditions similar to natural scenes to allow for independent variation of stimulus strength and mean luminance, which is not possible with the conventional flash ERG. TRANSLATIONAL RELEVANCE The white noise ERG methodology will be of benefit for clinical studies and animal models in the evaluation of hypotheses related to cellular redundancy to understand the effects of disease on specific visual pathways.
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Affiliation(s)
- Andrew J. Zele
- Visual Science Laboratory, Institute of Health and Biomedical Innovation, School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, Australia
| | - Beatrix Feigl
- Medical Retina Laboratory, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Australia
- Queensland Eye Institute, South Brisbane, Australia
| | - Pradeep K. Kambhampati
- Medical Retina Laboratory, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Australia
| | - Avinash Aher
- Laboratory for Retinal Physiology, Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany
| | - Declan McKeefry
- University of Bradford, Bradford School of Optometry and Vision Sciences, West Yorkshire, UK
| | - Neil Parry
- University of Bradford, Bradford School of Optometry and Vision Sciences, West Yorkshire, UK
- Vision Science Centre, Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - John Maguire
- University of Bradford, Bradford School of Optometry and Vision Sciences, West Yorkshire, UK
| | - Ian Murray
- Vision Science Centre, Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - Jan Kremers
- Laboratory for Retinal Physiology, Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany
- University of Bradford, Bradford School of Optometry and Vision Sciences, West Yorkshire, UK
- Department of Anatomy II, Friedrich-Alexander University Erlangen Nürnberg, Erlangen, Germany
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