Human cortical responses to binocular disparity and stereoscopic depth

Lead Research Organisation: University of Oxford
Department Name: Physiology Anatomy and Genetics

Abstract

Functional magnetic resonance imaging (fMRI) can be used to visualise activity in the brains of human subjects. When a region of the brain becomes active the neurons increase their activity. An increased flow of oxygen is required in that local region to fuel this activity. Since oxygenated (fresh) and de-oxygenated blood have different magnetic properties, it is possible to use the ratio of these two substances to measure changes in neural activity.

You may have seen ?Magic Eye? pictures in which an object ?jumps? out in depth from the page of a book. This is because there is a slight difference in the images going to the two eyes: it is known as stereoscopic depth perception. Using stimuli similar to these Magic Eye pictures, we can employ fMRI to investigate which areas of the human brain are responsible for producing this depth percept from the small differences in the images.

Deficits in depth perception are common, as any misalignment of the two eyes during early childhood due to ?squint? or ?lazy eye? can prevent the development of neurons that receive input from both eyes. Although the eyes can be realigned surgically, most children do not regain their binocular vision. Once we have established the areas of the brain involved in depth perception, it will be possible to compare the effectiveness of different treatments for these deficits.

Technical Summary

In natural viewing, humans acquire information about the depth of objects from the slightly different views of the scene obtained by the left and right eyes. In the laboratory, the same information can be provided simply by adding a slight horizontal offset (binocular disparity) to regions of the images presented to the two eyes. Our earlier neurophysiological studies demonstrate that multiple computational steps are required in the visual cortex to produce this depth percept.

This project will use functional magnetic resonance imaging (fMRI) to investigate the stages in the human visual cortex that begin with the detection and measurement of binocular disparity and lead to the perception of depth. This brain scanning technique is particularly valuable because cortical activity can be measured simultaneously across all visual areas while human subjects perform a perceptual task.

Based on neurophysiological results in animal studies, we propose four experiments.
The combination of these experiments will allow us to describe the network of areas involved in the computation of binocular depth perception from binocular disparity.
(1) Comparison between the response to correlated and anticorrelated random dot stereograms (RDS). While V1 neurons respond to both types of RDS, anticorrelated RDS do not deliver a consistent depth percept. Visual areas that reflect perceptual judgments should respond only to correlated RDS. (2) Investigation of absolute and relative disparity. Early stages of vision measure binocular disparity with respect to where the eyes are aligned (absolute disparity), whilst later stages that dominate perception compare the disparity between two or more visible features (relative disparity). (3) Separation of local and global disparity information using sinewave grating stimuli. When a disparity is added to a patch of grating, V1 neurons respond to the local disparity of each individual bar of the grating, but subjects report the global change in depth of the patch. (4) Cancellation of spatial disparities in depth perception. Binocular depth perception in dynamic patterns can also be produced by an interocular delay, which can be expressed as a temporal disparity. Spatial and temporal disparity can be traded off against each other to produce a stimulus that contains spatial binocular disparity, but is perceived as flat.

Once we have an understanding of the normal system of depth perception it will be possible to compare the cortical responses of subjects who lack functional stereoscopic vision and, in the longer term, to evaluate corrective therapy of such deficits.

Publications

10 25 50
publication icon
Bridge H (2013) Structural and functional changes across the visual cortex of a patient with visual form agnosia. in The Journal of neuroscience : the official journal of the Society for Neuroscience

publication icon
Bridge H (2016) Effects of cortical damage on binocular depth perception. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

publication icon
Bridge H (2016) Adaptive Pulvinar Circuitry Supports Visual Cognition. in Trends in cognitive sciences

publication icon
Ip IB (2014) Responses to interocular disparity correlation in the human cerebral cortex. in Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)

publication icon
Krug K (2017) The neural events that change perception in e-Neuroforum

 
Description Oxford Ophthalmology Symposium
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
Impact Updated clinical practitioners on potential uses of MRI imaging for neuro-ophthalmological investigations
 
Description MRC Collaboration Grant
Amount £4,923,554 (GBP)
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 02/2008 
End 01/2013
 
Description MRC Collaboration Grant
Amount £4,923,554 (GBP)
Funding ID G0700399 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 02/2008 
End 01/2013
 
Description MRC Research Grant
Amount £381,000 (GBP)
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 03/2009 
End 09/2012
 
Description Royal Society University Research Fellowship (to HB)
Amount £500,000 (GBP)
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 08/2009 
End 12/2015
 
Description Investigation of stereoscopic vision in an agnosic individual 
Organisation Durham University
Department Department of Psychology
Country United Kingdom 
Sector Academic/University 
PI Contribution Psychophysical testing Evaluation of visual function using magnetic resonance imaging
Collaborator Contribution Access to individual agnosic participant Behavioural testing of visionBehavioural testing of visual function in agnosic individual and typical participants
Impact Plenary Lecture at British Neuroscience Association PLoS One. 2010 Sep 7;5(9):e12608. Stereoscopic vision in the absence of the lateral occipital cortex. Read JC, Phillipson GP, Serrano-Pedraza I, Milner AD, Parker AJ.
Start Year 2007
 
Description Investigation of stereoscopic vision in an agnosic individual 
Organisation Newcastle University
Department School of Psychology
Country United Kingdom 
Sector Academic/University 
PI Contribution Psychophysical testing Evaluation of visual function using magnetic resonance imaging
Collaborator Contribution Access to individual agnosic participant Behavioural testing of visionBehavioural testing of visual function in agnosic individual and typical participants
Impact Plenary Lecture at British Neuroscience Association PLoS One. 2010 Sep 7;5(9):e12608. Stereoscopic vision in the absence of the lateral occipital cortex. Read JC, Phillipson GP, Serrano-Pedraza I, Milner AD, Parker AJ.
Start Year 2007
 
Description A-level days 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Related to the Brain Diaries exhibition run at the Natural History Museum, we put together a day for A-level students about the brain, MRI and vision. The day had interactive talks in the morning and then activities in the afternoon. It was so successful that we ran it a second time.
Year(s) Of Engagement Activity 2017
 
Description Brain Diaries 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact I contributed to a Neuroscience Exhibition at the Natural History museum in Oxford that ran from April 2017 until December 2017. As part of this we ran a competition that attracted over 750 entries. Thousands of people saw the exhibition and I also took a group of visually impaired people through the exhibition.
Year(s) Of Engagement Activity 2017
URL http://www.oum.ox.ac.uk/braindiaries/
 
Description Christmas Lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Around 300 pupils attended a Christmas lecture demonstrating how the visual system system works and how we use MRI to understand it. Excellent feedback from pupils was received.
Year(s) Of Engagement Activity 2017,2018
 
Description Curiosity Carnival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact We scripted and acted in a lighthearted play about the brain and how we understand its function. It has been performed 3 times, first at the European Researchers Night in September and then twice at a public event at the Natural History Museum in Oxford.
Year(s) Of Engagement Activity 2017
 
Description Hay Festival 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact I participated in a debate and a discussion workshop at Hay Literary Festival.
Year(s) Of Engagement Activity 2015
 
Description International Risk Assessment and Horizon Scanning Symposium 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact A two-day multi-disciplinary symposium to provide advice to the Singapore Goverment and other policy-making bodies

See http://www.rahs.org.sg/t2_irahss08_ats.html
Year(s) Of Engagement Activity 2008
 
Description Lecture in Blouin Institute Art Gallery 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Public Lecture in Art Gallery

Collaboration with Prof Martin Kemp, History of Art, Oxford
Year(s) Of Engagement Activity 2007
 
Description Vision in the Real World 
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 The York University
Centre for Vision Research
and the
Vision: Science to Applications Program


International Conference
on Vision in the Real World

Recital Hall, Accolade East Building
June 13-16, 2017
Year(s) Of Engagement Activity 2017