Multiple signals interact in flicker: recursive surround networks

Lead Research Organisation: University College London
Department Name: Institute of Ophthalmology

Abstract

Before visual stimuli arriving at the eye are consciously perceived they are transformed and encoded by multiple circuits in the intervening visual pathways. These processes subtly alter our perception of visual stimuli. Many of the processes cannot be directly observed - they are carried out by very small neurons with a very large number of even smaller connectors and it is the whole nest of these complex interconnections that determine the way the nest behaves. One way to determine some of the characteristics of these inaccessible processes is to study behaviour that depends on them. Our aim is to determine how the circuitry of the human visual system works through careful perceptual measurements of flicker perception. We rely on the fact that interactions between different circuits within the visual system alter visual signals in characteristic ways. Typically, these interactions cause flicker to be relatively less visible at some frequencies but easy to see at other frequencies. By looking for those characteristic effects in perceptual measurements, we can tease apart the different underlying visual circuits and their contributions to perception. In previous work, we discovered a surprisingly complex circuitry that uses the signals from the individual light receptors-cones-in several different and unexpected ways. In this project, we propose to monitor and model those signals under a variety of new conditions to understand more about how the eye and brain work. We confidently expect to provide a greater understanding of vision and visual processing, which will yield important benefits in other areas of vision research, and will help to bridge the widening gap between relatively simple models of the visual pathways and what we are now learning about the complex structure and function of the visual system from other disciplines.

Technical Summary

The primary aim is to elucidate the functional circuitry of the human visual system through psychophysical experiments. Our approach is based on the prediction that different visual circuits produce signals with amplitudes and delays that vary with temporal frequency in characteristically different ways. We successfully used this approach to identify-in addition to the expected, fast positive M- and L-cone inputs-sluggish middle(M)- and long(L)-wavelength-sensitive-cone inputs of both positive and negative sign into the luminance or achromatic pathway. The measurements were made on deep-red (658-nm) adapting fields. We propose to make extensive measurements using other adapting field wavelengths to determine the influence of wavelength and intensity on the relative strengths of the various cone inputs into the human luminance channel. As before, a vector model will be used to analyse the data and identify the signs and strengths of the various inputs. Preliminary evidence shows sluggish inputs are clearly evident on adapting fields of short and middle-wavelengths. We confidently expect to produce a more realistic model of the human visual system and human visual processing, and, by characterizing the signals that are accessible by observers and evident in their behaviour, help to provide new links between behavioural and physiological experiments.

Planned Impact

The primary goal of this research project is the elucidation of fundamental properties of the human and primate visual system. Consequently, the initial beneficiaries of this research will be other scientists studying the visual system. These will include not just visual psychophysicists like the PI, but also sensory physiologists, electrophysiologists and cognitive neuroscientists working on visual processing in the human and primate visual system. The initial impact will be, we expect, the provision of a model of early visual processing that identifies the visually significant signals that should also be evident using other objective measurements. Many other scientists, who are less directly involved in vision research, including some geneticists, anatomists working on the early stages of the visual system, and brain-imaging specialists will also potentially benefit from this research. At the more applied level, this work may also benefit engineers interested in the ergonomics of man-machine interfaces. Such interfaces and displays include videos, films, mobile phones and other dynamic presentation devices.
Longer term benefits will include clinical applications of the research. Once we have defined and modelled the characteristics of visual processing in normal observers, we can make comparable measurements in patients with specific clinical visual deficits. As we have found with other similar paradigms, this can be very fruitful in way of understanding the nature of the clinical deficit. We already have several ongoing collaborations with our sister institution Moorfields Eye Hospital.
Given the wide range of interest in vision research across many disciplines it will be important that our results and models are widely disseminated. We will publish our work in open source journals and present the data at international conferences. As part of this project, we also propose to make our data available at the Colour and Vision Research Laboratory (CVRL) website run by the PI at http://www.cvrl.org This resource is well-known and widely used in colour research both by academics and in industry. We propose to develop this resource further to provide general information on vision.

Publications

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Stockman A (2016) Handbook of Color Psychology

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Conway BR (2018) A tour of contemporary color vision research. in Vision research

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Bainbridge JW (2015) Long-term effect of gene therapy on Leber's congenital amaurosis. in The New England journal of medicine

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Rider AT (2018) Harmonics added to a flickering light can upset the balance between ON and OFF pathways to produce illusory colors. in Proceedings of the National Academy of Sciences of the United States of America

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Stockman A (2017) Linear-nonlinear models of the red-green chromatic pathway. in Journal of vision

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Stockman A (2018) Delayed cone-opponent signals in the luminance pathway. in Journal of vision

 
Description Psychophysical measurements reveal clear evidence for antagonistic and synergistic interactions between visual responses generated by uniform fields of flickering light. Such light generates fast or slow responses with the slower responses' being delayed by tens of milliseconds and being of either the same or the opposite sign as the faster response.
The interactions of fast and slow responses can be clearly seen in the delays between pairs of S-, M- or L-cone flicker stimuli measured using a flicker-photometric cancellation technique, which expose ubiquitous and often sizeable delays between the various responses. The interactions can alter the shape of temporal contrast sensitivities depending on the frequencies at which the responses constructively or destructively interfere. Cone signals in the luminance or achromatic pathway were investigated by measuring how the perceptual timing of M- or L-cone-detected flicker depended on temporal frequency and chromatic adaptation. Relative timings were measured, as a function of temporal frequency, by superimposing M- or L-cone-isolating flicker on "equichromatic" flicker (of the same wavelength as the background) and asking the observer to vary contrast and phase to cancel the perception of flicker. Measurements were made in four observers on up to 35 different backgrounds varying in wavelength and radiance.
Observers showed substantial perceptual delays or advances of L- and M-cone flicker that varied systematically with cone class, background wavelength, and radiance. Delays were largest for M-cone-isolating flicker. Although complex, the results can be accounted for by a surprisingly simple model in which the representations of L- and M-cone flicker are comprised not only of a fast copy of the flicker signal, but also of a slow copy that is delayed by roughly 30 ms and varies in strength and sign with both background wavelength and radiance. The delays, which are too large to be due to selective cone adaptation by chromatic backgrounds, must arise postreceptorally. Clear evidence for the slow signals can be found in physiological measurements of horizontal and magnocellular ganglion cells, thus placing the origin of the slow signals in the retina-most likely in an extended horizontal cell network. Luminance-equated stimuli chosen to isolate chromatic channels may inadvertently generate slow signals in the luminance channel.
Exploitation Route This is an ongoing grant and we are continuing this research work.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Other

 
Title CVRL database 
Description This web resource provides an annotated database of downloadable standard functions and data sets relevant to colour and vision research and to colour technology, as well as providing information about the research outputs of our group. Updated frequently. 
Type Of Material Database/Collection of data 
Year Produced 2006 
Provided To Others? Yes  
Impact Widely used in science and industry, the site started at UC San Diego in 1995 and moved to UCL with the PI in 2001. 
URL http://www.cvrl.org
 
Description BBC World Service, CrowdScience participant. 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact CrowdScience participant as an expert on colour vision.
Year(s) Of Engagement Activity 2018
 
Description Invited speaker, 16th International Symposium on the Science and Technology of Lighting, Sheffield 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact 100 attendees and the talk sparked discussion about human vision and lighting.
Year(s) Of Engagement Activity 2018
 
Description Invited speaker, OSA Fall Vision Meeting, Reno, US 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact About 300 attendees. Talk stimulated considerable debate.
Year(s) Of Engagement Activity 2018
 
Description Invited speaker, UP.GRADE seminar on Human vision and color pipelines, Camerimage, Bydgoszcz, Poland. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Keynote speaker on human colour vision at international film festival.
Year(s) Of Engagement Activity 2017
 
Description Invited talk, Department of Psychology, University of Washington 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Seminar presentation. Talk stimulated useful and interesting discussion.
Year(s) Of Engagement Activity 2018
 
Description Keynote speaker, 2nd International conference colour in film, British Film Institute and Colour Group GB. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation on visual illusions to film makers.
Year(s) Of Engagement Activity 2017
 
Description Lecturer, ICVS summer school, Oxford. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact International school on colour vision held every two years bu the International Colour Vision Society. Educationally important.
Year(s) Of Engagement Activity 2018
 
Description Lecturer, ICVS summer school, Oxford. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Participant in one week summer school on colour vision.
Year(s) Of Engagement Activity 2016
 
Description Ophthalmology Grand Rounds talk, Department of Ophthalmology and Visual Sciences, University of British Columbia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Clinical vision talk that was broadcast around British Columbia. Significant positive feedback and interest.
Year(s) Of Engagement Activity 2018
 
Description PI was chair and co-chair of the Colour Group GB 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact The Colour Group GB organizes public meetings, school lectures and events on the broad topic of colour.

Wider interest and appreciation of the scientific and artistic aspects of colour.
Year(s) Of Engagement Activity 2009,2010,2011,2012,2013,2014
URL http://www.colour.org.uk
 
Description Public lecture on Human Colour Vision IOP Canterbury 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Public lecture on Human Colour Vision IOP Canterbury
Year(s) Of Engagement Activity 2016
URL http://www.iop.org
 
Description Public lecture on Human Colour Vision IOP London 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Colour Vision
Public lecture at the Institute of Physics London
Year(s) Of Engagement Activity 2016
URL http://www.iop.org/
 
Description Public lecture on Human Colour Vision IOP Open University 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Colour vision
Invited public lecture, Institute of Physics, Open University, Milton Keynes
Year(s) Of Engagement Activity 2016
URL http://www.iop.org/
 
Description Short course instructor, 24th Color and Imaging Conference, San Diego 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact 2 hour short course on "Cone fundamentals, color matching functions, luminous efficiency and individual differences".
Year(s) Of Engagement Activity 2016
 
Description Short course instructor, 25th Color and Imaging Conference, Lillehammer 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact 2 hour short course on "Cone fundamentals, color matching functions, luminous efficiency and individual differences"
Year(s) Of Engagement Activity 2017
 
Description Short course instructor, 26th Color and Imaging Conference, Vancouver. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Class and workshop in colour and colour vision for people in Colour and imaging. Important for forging links with industry.
Year(s) Of Engagement Activity 2018
 
Description TEDxUAL talk on Color Vision 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact TEDxUAL speaker, University of the Arts London. On-line
Year(s) Of Engagement Activity 2016
URL http://www.tedxual.com/
 
Description UC Davis, Vision Sciences seminar speaker 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Local seminar. Produced good discussion. Lab visits there were very useful and interesting.
Year(s) Of Engagement Activity 2018
 
Description UC San Diego, Department of Psychology Colloquium speaker 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Colloquium audience at UC San Diego. Sparked questions and discussion,
Year(s) Of Engagement Activity 2018
 
Description Visual Cognition talk, Department of Ophthalmology and Visual Sciences, University of British Columbia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact About 60 attendees enjoyed a talk on colour vision that led to useful discussions and feedback.
Year(s) Of Engagement Activity 2018