Brain research helps us to understand how different people's brains work. At the moment, various types of brain research are being carried out which will help us to find out more about autism spectrum disorder (ASD).
This information will tell you more about:
- why it is important to study the brain in relation to ASD
- the different ways in which researchers are studying the brain
- how research may lead to better support or treatments for people with an ASD.
Why study the brain?
Finding out how the brain works is extremely difficult as the brain is so complex. Brain research is important as it helps us understand how the average brain functions and what we can do when things go wrong (for example, after a head injury).
Understanding how the brain works in different people is important, too. Many features of ASD - such as difficulties with social interaction, the use and understanding of language, or repetitive behaviours - are a result of how the brain is structured, and how it works. If we find out more about brain structure and function, we will better understand the difficulties faced by people with an ASD - but also their strengths. We will also be able to develop better support and treatments.
Ways of finding out more about the brain
Different techniques can be used to explore the human brain. These include:
- brain imaging, which lets us look inside the living brain, and see how it is structured and how it works
- looking at the electrical activity of the brain to find out what it is doing
- post-mortem study of a brain, where scientists look at the individual cells of the brain after a person has died.
We will look at all of the techniques used for exploring the brain.
Developments in technology mean that we can now easily and harmlessly look inside someone's brain. This is called brain imaging, or scanning. The person may be asked to actively think about certain things while their brain is being scanned, or they may be resting and not thinking about anything in particular.
Brain scanning usually involves a technique called 'magnetic resonance imaging' (MRI). A special scanner, called an MRI scanner (pictured - essentially a big magnet) is used. The scanner looks like a capsule and can look at any part of the body, including the brain. If you were to have an MRI scan, you would lie inside the scanner. It can be noisy in the scanner because of the magnet, but the scan is completely non-invasive: all you do is lie there. You can have many scans over the course of your life. This means that MRI scans are great for research that explores the development of the brain over time.
Brain imaging explores either the structure or the function of the brain.
A structural MRI (pictured) explores both the overall size and shape of the brain, and specific parts of it. By comparing the brain scans of separate groups of people (for example, people with an ASD and people without) we can look for differences in the way their brains are structured. We can also see how people's brains develop over time by scanning them at different ages.
With a new technique called 'diffusion tensor imaging' (DTI), we can also look at the connections between different brain structures. This is of interest because it may be that with autism, the manner in which nerve cells are connected together differs slightly and this could be shown up by this type of imaging.
Structural imaging has taught us that:
- people with an ASD may have larger brains
- in early childhood, the brains of people with an ASD grow unusually fast
- brain structure may be different in people with an ASD, but research findings are inconsistent
- the connections between different areas of the brain may be different in people with an ASD.
Functional imaging (or fMRI scans) gives us information about brain activity and which parts of the brain are doing things while people are engaged in particular tasks. We do this by giving someone simple tasks to do while they are being scanned. The scan detects the amount of oxygen that is extracted from the blood by different parts of the brain. The more oxygen that is being extracted, the harder that part of the brain is working. The coloured overlay on the fMRI scan pictured shows the regions of a person's brain that were active during a 'theory of mind' task
fMRI scans are harder to interpret than structural MRI scans because the activity in the brain depends on how much the person is concentrating on the task in hand. You never know, their thoughts may have wandered instead to the shopping they have to do when they get home! We can try to manage this by asking the person to simply lie in the scanner for a bit, to do 'control tasks' and then to do the real task. When the real task is done we can see exactly which parts of the brain are at work, and compare this to activity on the control tasks and when doing nothing.
Functional imaging has taught us that:
- parts of the brain that are typically involved in understanding emotions have different patterns of activity in people with an ASD
- parts of the brain involved in recognising faces have different patterns of activity in people with an ASD (in fact they may not be active at all)
- parts of the brain that are active when we take part in social activities may be affected in people with an ASD.
The future for brain imaging research
There is still much we don't know about the brain, but brain imaging will help us to find out more. There are a number of areas where research will be carried out.
- How brain structure may relate to ASD. For example, studies that follow infant siblings of children with an ASD over time can examine how changes in the structure of the developing brain relate to the onset of behaviour associated with ASD (including strengths and special skills).
- How genetic differences may relate to structural and functional differences in the brain, and in turn to the development of ASD.
- How structural differences in the brain may be used to diagnose an ASD. This is still a long way off, but if consistent patterns of structural brain differences are found in people with an ASD, a brain scan may help with diagnosis.
- We may be able to see which approaches help people with an ASD not only by monitoring changes to their skills and abilities, but by looking at corresponding changes in parts of the brain that relate to those skills and abilities.
Electrical activity in the brain
The brain works when electrical impulses travel in the nerve cells and 'chemical messengers' are released between one cell and others that it connects with. The electrical activity (which is very small) generates a tiny magnetic field which can be detected by sensors outside the skull. This is called magnetoencephalography (MEG). The picture shows the MEG scanner at CUBRIC (Cardiff University Brain Research and Imaging Centre) and the information it can give us.
MEG is completely non-invasive and can tell us precisely where an electrical current in the brain is generated. It can also tell us about the time course and intensity of the electrical brain activity. Because electricity travels at the speed of light, MEG is better at measuring brain activity than fMRI scans, which measure the relatively slow movement of blood to groups of brain cells.
Another technique which is used to measure electrical activity in the brain is called electroencephalography (EEG). This involves putting electrodes on the scalp that measure electrical impulses in groups of brain cells (pictured). The technique is harmless and doesn't hurt.
An EEG can tell researchers about the intensity and time course of electrical activity in the brain when a person is asked to do a particular task. However, the electrical signal measured in an EEG can be distorted by the skull. Therefore, an MEG can give a better indication of the source of electrical signals in the brain.
MEG and EEG research has told us that:
- there are differences in the location of electrical activity in the brain in people with an ASD
- there are differences in the time course of electrical activity in the brain in people with an ASD
- communication between different regions of the brain is reduced in people with an ASD
- the brain receives a lot of information from the world and processing some of this information takes more time for people with an ASD.
Measuring electrical activity in the brain can also help people with epilepsy, which some people with an ASD also have. In some cases a surgeon may be able to stop epileptic seizures by removing a very small part of the brain where excessive electrical discharges are generated.
Post-mortem brain study
Brain imaging and MEG and EEG research have greatly increased our understanding of the subtle differences in the brains of people with an ASD. However, they can't tell us everything. We can't see individual brain cells or very small, but important, molecular structures or fully understand the effects genetic differences have on brain tissue.
The only way to study brain cells and molecular structure is to examine the brain after death. It was post-mortem studies that showed how a brain chemical called dopamine was reduced in people who had Parkinson's disease. This led to the development of quite an effective treatment to replace lost dopamine.
Post-mortem research uses brains that people have donated for this purpose (see www.brainbankforautism.org.uk). The research has to be carried out with the permission and approval of experienced ethics committees.
A woman with Asperger syndrome donated her brain to the Brain Bank for Autism when she discovered that she had cancer at the age of 44. She said:
Since I found the website for the brain bank and decided to donate my brain for research into autism, I now know that something really positive will come from my life. It will help others in the future if this work can increase the understanding of autism. My main concern since I decided to give my brain has been to make sure that [my mother] will feel OK about it and that she understands why I want to do it. We have now had a long talk and I am glad to say that she is 100% behind me.
Post-mortem brain studies have already told us several significant things.
- There are some important cell differences in the brains of people with an ASD. For example, oxytocin-synthesising nerve cells (pictured right) are found in the hypothalamus, a region of the brain. Oxytocin is a hormone that is also used as a chemical transmitter between nerve cells in the brain, and it has an influence on social behaviour. It has been found that there is less oxytocin receptor - the molecule that enables oxytocin to exert effects in the brain - expression in the brain in autism.
- The brain can be imaged in much the same way after death as in life (known as post-mortem imaging). After looking at post-mortem brain images, scientists can explore the actual brain tissue - look at the molecules and cells where differences in the brain have been found. This will help to reveal the cause of those differences. Scientists may place brain tissue under a microscope or using chemical techniques. The picture above shows an image of nerve cells in the hippocampus area of the brain, which helps regulate emotion and memory.
- Brain tissue can be used to show which 'gene products' - chemical instructions that 'tell' a cell which proteins to synthesise and activate - in the brain may be reduced (or increased) in people with an ASD. This will help to improve our understanding of the causes of ASD and how genetic changes lead to changes in brain development, structure or function.
The future for post-mortem brain studies
It may prove possible to influence the genetic instructions operating in some cells in the brain, for example, by means of education, altering diet or by giving treatment with hormones or drugs that can fine-tune brain function.
It may, eventually, be possible to influence the way the brain develops its connections in early childhood so that some of the difficulties that people with an ASD can experience are reduced.
There is also interest in finding out how brain structure may relate to special skills that people with an ASD can have.
Taking part in research
If you are interested in taking part in research into ASD, you can find out about studies that are looking for participants at www.autism.org.uk/research
References and recommended reading
Abrahams, B. S. and Geschwind, D. H. (2010). Connecting genes to brain in the autism spectrum disorders. Archives of Neurology, 67 (4), 395-99.
Amaral, D. G. et al (2008). Neuroanatomy of autism. Trends in Neuroscience, 31 (3), 137-45.
Ecker, C. et al (2010). Describing the brain in autism in 5 dimensions - magnetic resonance imaging-assisted diagnosis of autism spectrum disorder using a multiparameter classification approach. Journal of Neuroscience, 30 (2), 10612-23.
Grandin, T. (1996). Thinking in pictures and other reports from my life with autism. New York: Vintage Books. ISBN: 0679772898.
Minshew, N. J. and Williams, D. L. (2007). The new neurobiology of autism: cortex, connectivity and neuronal organization. Archives of Neurology, 64 (7), 945-50.
Williams, M. A. and Sachdev, P. S. (2010). Magnetoencephalography in neuropsychiatry: ready for application? Current Opinion in Psychiatry, e-publication ahead of print.
Written by Dr Gina Gomez de la Cuesta, Action Research Leader, The National Autistic Society, and Margaret Esiri, Professor of Neuropathology, Oxford University.
Thanks to Brenda Nally at the Brain Bank for Autism and Related Developmental Research, Oxford University; Lorna Wing; and researchers at the University of Cambridge for their help with this information about brain research and autism.
Thanks also to Dr Sarah Carrington at the Wales Autism Research Centre, Cardiff, for her help with securing permission to reproduce the images used here.