Understanding Degeneration and the Capacity for Reorganisation in the Adult Human Visual Cortex

Lead Research Organisation: University of Oxford
Department Name: Clinical Neurosciences

Abstract

Loss of vision in infancy results in functional reorganisation of the visual cortex1-3;
this shows how the brain can adapt to an altered sensory input early in life. Much less
is known about how the adult brain reorganises in response to abnormal visual input
or how it might adapt to treatments that try to restore visual function. Since inherited
retinal diseases are the leading cause of blindness in the developed world, the demand
for therapy will increase in the next decade. Even where therapy is available, the brain
needs to be able to interpret the restored sensory input, and it is not clear whether this
will be possible following prolonged loss of input. In order to optimally restore
function it is vital to understand the principles of how the adult brain responds to a
loss of sensory input.
Stargardt disease (STGD) is a type of retinal disease in which central vision is most
affected. This project will measure the longitudinal changes in the visual system of
patients with STGD and will be completed under the supervision of Professor Holly
Bridge.
Aims
1) Cortical effects of retinal degeneration in STGD
Previous research has investigated structural and functional cortical changes in retinal
diseases4, 5. 25 STGD patients and 25 age-matched controls will be recruited to
undertake a cross-sectional investigation of the cortical changes associated with
STGD. This will be measured using Magnetic resonance spectroscopy imaging
(MRSI), structural MRI, diffusion-weighted imaging and population receptive field
(pRF) mapping. Clinical measures of retinal function will then be compared to these
measures.
2) Longitudinal investigation of reorganisation due to degeneration in STGD
Since retinal degeneration can be rapid in STGD, many patients show a decrease in
visual function after two years. To quantify the effects of this loss of input and
function on the visual cortex, patients will be rescanned after two years. By measuring
differences in the same MRI quantities, I will be able to directly demonstrate the
effects of retinal degeneration on the brain.
3) Assessing the potential for boosting plasticity in the healthy visual system
Increasing excitability in the brain is thought to boost the amount of reorganisation
that can take place; studies in adult animals have shown that this change can occur
when manipulating the neurochemical environment6. In order to maximise visual
function following visual restoration it may be necessary to boost the ability of the
cortex to respond to restored input. In the motor system tDCS has been used as an
adjunct procedure to increase behavioural effects of training or rehabilitation7, much
less is known of its effects in the visual system. 20 volunteers will be scanned using
MRSI and fMRI (7T) to investigate changes that occur following tDCS application
firstly to the occipital pole, and secondly to hMT+.
To summarise, this project will determine the direct consequences of visual loss due
to retinal degeneration, specifically the changes that occur in individual patients over
time. Additionally, this project will assess the potential to boost plasticity in the visual
system using tDCS, which may be important for optimising visual function.

Publications

10 25 50
 
Description Understanding Degeneration and the Capacity for Reorganisation in the Adult Human Visual Cortex
Amount £77,822 (GBP)
Funding ID 1959793 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 10/2017 
End 09/2020
 
Title Database 
Description I collected a novel dataset which is currently one of the largest imaging datasets on patients with retinal disease. I tested 58 participants (20 choroideremia, 17 Stargardt and 21 age matched controls with healthy vision). They were tested with Magnetic Resonance Imaging (MRI) (structural, functional and neurochemical scans) and vision testing (microperimetry, optical coherence tomography, colour vision). 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? No  
Impact The research will inform on the how a lack of visual input from eye disease affects the visual cortex and if this may hinder therapies to restore vision at the eye. 
 
Description Population receptive field mapping 
Organisation Amsterdam Medical Center
Country Netherlands 
Sector Hospitals 
PI Contribution I have collected functional neuroimaging data on our patients and controls. With this data we can use a technique called population receptive field (pRF) mapping which functionally maps the visual field into the brain. We are using the techniques developed in the Dumoulin lab to analyse this data.
Collaborator Contribution The Dumoulin lab developed this technique and taught ,e how to use it. We have further developments to use it in my data.
Impact There are no outcomes yet as the data analysis is still in process.
Start Year 2019
 
Description Big Brain Roadshow 
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 We created the Big Brain Roadshow, which consists fo a team of researchers in my department who tour high schools across Oxfordshire and deliver a play on how brain imaging has changed since the 1800's. We then have stalls on the different parts of our research areas for the students to interact with (vision, movement, development, physics). I participated in the play and ran the vision stall on visual illusions and how they relate to the different areas of the visual system.
Year(s) Of Engagement Activity 2019
 
Description Live Brain Scan Experiment 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact I was part of organising a live brain scan experiment on The Big Questions podcast. This experiment was designed by the winner of the Brain Diaries exhibition competition at the Oxford University of Natural History, there were 700 competition entries. Researchers asked the general public what they would like to find out if they had access to an MRI scanner. The winning question was chosen and the experiment was streamed live on the Oxford Sparks Facebook channel. The experiment asked: How does he brain identify voices?
Year(s) Of Engagement Activity 2018
URL https://www.oxfordsparks.ox.ac.uk/content/how-does-brain-identify-voices
 
Description Oxford Sparks Twitter Take Over 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact For brain awareness week myself and another colleague had a full day each to post on the OxfordSparks Twitter about our research to the OxfordSparks 8,000 followers. I tweeted about my research, interesting facts on the visual system and neuroscience myths.
Year(s) Of Engagement Activity 2017
URL https://www.oxfordsparks.ox.ac.uk/content/twitter-takeovers-brain-discovery-week