Week 4: Explaining autism: mind and brain

In Weeks 1 to 3, you gained a picture of how the behaviour and thinking style of autistic people may differ from that of neurotypical people, and you have learned which of these key differences form the basis for diagnosis. But how and why do such differences come about? This is a question that scientists have tried to answer, offering explanations or theories about the psychology of autism (how the mind works), the neurobiology (structure and function of the brain and nervous system), and genetics (the influence of genes in a person’s physical and psychological traits, in this case making autism more likely to occur in some people than others). This week we will consider selected highlights of this scientific work. Notice that some of these studies consider relationships between different levels (psychology, neurobiology and genetics).

Now watch the following video in which Dr Ilona Roth introduces this week’s work.

Download this video clip.Video player: boc_aut_1_video_week4_intro.mp4

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INSTRUCTOR:

By now, you should have a good feel for key characteristics of autism, but how and why does autism come about? This week, you'll be learning how scientists have tried to answer these questions, offering a range of explanations or theories based on their research. You'll look at some psychological theories focusing on how the mind works; neurobiological theories, dealing with structure and function of the brain and nervous system; and genetics-- insights into the genes underlying traits particularly associated with autism. There's a huge amount of scientific work on autism, and only a fraction can be covered in your week's study.

Starting with psychology, one influential theory is that autistic people tend to have difficulty understanding what other people think and feel, leading them to misread social situations. Another key theory links autistic people's strong preference for structure and routine to difficulty with mental flexibility and planning. Two further theories make connections between the difficulties and the strengths in autism. Some neurobiological theories suggest that subtle atypicalities in brain structure and function play a role in autism. Further neurobiological work focuses on differences in how information is transmitted via nerve fibres and on the action of certain hormones.

The genetics of autism is both compelling and complex. The fact that autism can affect more than one member of the same family provides strong evidence for a genetic influence. But a huge number of candidate genes have been identified, and these seem to vary from one individual to another. Explanations of autism have progressed a lot since the early days, but there's not often a straightforward translation between scientific findings and practical solutions that help autistic people.

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By the end of this week you should be able to:

• understand key approaches to explaining autism
• differentiate three levels of explanation: psychological, neurobiological and genetic
• understand key psychological accounts of the autistic ‘thinking style’ and identify implications for everyday life
• appreciate key ideas about brain and nervous system function in autism
• appreciate the complex role of genetic influences in autism.

Psychological theories of autism seek to explain the characteristic behaviour and thinking style in terms of underlying psychological processes, that is, how autistic people process information about other people and the environment. Some theories have a primary focus on either the social traits or the non-social traits, so these theories are not mutually exclusive. Further theories have tried to bring the social and non-social areas of difference together within a single framework.

We will start with the theory known, confusingly, as ‘Theory of Mind’ theory, which is probably the most influential explanation of the social challenges in autism.

Back in the 1980s, autism researchers Simon Baron-Cohen, Uta Frith and Alan Leslie set out to investigate why children and adults with autism seemed prone to misunderstanding social situations, and were claimed to be unaware of other people’s feelings. They devised an elegant psychological test which suggested that most children with autism have great difficulty in ‘putting themselves in another person’s shoes’, that is, understanding that others have thoughts, knowledge, beliefs, desires and goals which may differ from their own. This difficulty in understanding other people’s thoughts and points of view is known as a Theory of Mind (ToM) or ‘mindreading’ problem (Baron-Cohen, Leslie and Frith, 1983).

The task, developed by Baron-Cohen and his colleagues and used frequently in subsequent studies, is known as the Sally–Anne false belief task. Before watching the animation illustrating the task (Activity 1), consider the following imaginary scenario, an everyday example of the kind of skill that Baron-Cohen was exploring.

You and a friend, Kelly, drive to the shops in your car. You park in a particular street (Mount Street) and as you both have different shops to visit, you arrange to meet back at the car in an hour’s time. Shortly after parting from your friend, you realise that you have left your wallet at home, so you drive home to fetch it. When you get back to where you parked before, the parking spaces are full, so you have to park in a different street (Park Street). You know that when Kelly goes to meet you she will have the false belief that the car is where you originally parked it. Unless you can contact her first, she will go to meet you in Mount Street, not in Park Street.

Of course these days, mobile phones offer a ready solution to problems like this. The point is to illustrate what neurotypical people routinely understand or figure out about what another person is thinking. Without an understanding that Kelly would hold a false belief about your meeting place, you would not even realise that it was necessary to redirect her! So the ability to understand false belief is an important aspect of understanding other people’s thoughts and beliefs – that is, theory of mind.

Activity 1 Try out the Sally–Anne false belief task

Timing: Allow about 10 minutes

Simon Baron-Cohen used the Sally–Anne task to investigate whether autistic children could understand false belief. The following download contains an animation that illustrates this test and his results. After watching the animation, answer the three questions that follow it, and pay careful attention to the feedback.

You can find the downloadable Sally–Anne task at this link.

You can find instructions for downloading and using the Sally–Anne task at this link.

If you can't use this download, or prefer not to, here is an image showing the key contents of the animation:

Figure 1 The Sally–Anne false belief task.

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This drawing contains a sequence of five drawings demonstrating the Sally–Anne task. The first drawing shows Sally, who has a basket, and Anne, who has a box. In the second drawing, Sally is shown holding a marble, and placing it in her basket. In the third drawing, Sally closes the basket and leaves the room. In the fourth drawing, Anne then removes the marble from the basket and puts it in the box instead. Then in the final drawing, Sally returns to the room. Text in the drawing explains that she wants to play with her marble, and asks 'Where will she look for it?'.

Figure 1 The Sally–Anne false belief task.

When this task is used with typically developing children, it is found that over the age of 4–5 years, most are able to correctly identify that Sally has a false belief about the location of the marble.

Activity 2 Children taking the Sally–Anne task

Timing: Allow about 10 minutes

Now watch a short video, in which Baron-Cohen first tested two children with autism and then a younger neurotypical child on the task. Notice that most children with autism (around 80%) fail on the ‘belief’ question ‘Where will Sally look for her marble?’, while children in the two control groups mostly pass. What does failure on the belief question suggest? Note down your explanation.

Download this video clip.Video player: aut_1_wk04_sally-anne-task_combined.mp4

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SIMON BARON-COHEN:

Her name is Sally.

SIMON BARON-COHEN:

All right? When Sally stands over there, then we've got another doll. And this one is called Anne.

BOY 1:

Yeah.

SIMON BARON-COHEN:

Anne's over there. Now which one is Anne? Good. And which one is Sally? Good.

Now look at this. Sally's got a yellow box.

This is a test of whether the child can appreciate that someone else might have a different belief about a situation to the child's own belief.

Sally has also got a little marble.

BOY 1:

Yeah.

SIMON BARON-COHEN:

And she puts it inside her yellow box. And now she goes for a walk. Off she goes.

BOY 1:

Yeah.

SIMON BARON-COHEN:

She's gone for a walk. Anne goes over to Sally's box, takes out the marble, and puts it into her blue box.

The child knows that the marble has been moved. The child has also seen that Sally has gone out of the room or left the scene when that transition occurred. So she shouldn't know that the objects now are being moved.

So when asked the question where will Sally look, to pass this test, the child should point to where Sally thinks it is rather than to where the marble really is.

Here comes Sally back from her walk.

BOY1:

Yeah.

SIMON BARON-COHEN:

Where will Sally look for her marble?

[TAP]

SIMON BARON-COHEN:

Right. And where was the marble in the beginning?

[TAP]

SIMON BARON-COHEN:

And where is the marble really?

[TAP]

SIMON BARON-COHEN:

Very good.

What we've seen with this autistic child and indeed with the majority that we've tested is that the child actually points to where the marble really is rather than to where Sally thinks it is and in this case demonstrates no ability to distinguish between their own belief and that of someone else's.

Here she is. Where will she look for her marble?

BOY 2:

Yellow box.

SIMON BARON-COHEN:

It's very important to actually rule out that maybe other non-autistic children might also have the same difficulty. So what we've done is to do exactly the same test with a group of non-autistic, what we could call normal kids of about four years old, and find the majority have no trouble at all with this task they can easily distinguish between where they know the object to be and where Sally falsely believes it to be.

Where will she look for her marble? Right. Now where is the marble really? That's right. Where was the marble in the beginning? Very good.

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Discussion

Baron-Cohen and his colleagues argued that instead of 'putting themselves in Sally's shoes', the autistic children assume that Sally’s belief about where she will find her marble is the same as their own knowledge of where the marble really is. In short, the study suggests that children with autism have difficulty understanding another person's thoughts, which in this case are different from their own.

The basic finding of the Sally–Anne task has been replicated (repeated with the same outcome) many times, with numerous variants of the task. However, the number of autistic children failing the Sally–Anne task does vary from one study to another.

Note that the task does not offer a way of diagnosing autism. Not all autistic people fail it, and some neurotypical people may also find it difficult.

Over the decades since the Sally-Anne false belief task findings were first reported, their implications have been widely questioned and qualified. However, a quite common occurrence in autism is that a person fails to give some crucial information to another person. This could well reflect a problem in understanding other people's knowledge of a situation.

ToM is about understanding other people’s mental states, that is their beliefs, intentions, feelings and so on. Some researchers have suggested a link between ToM difficulties and ‘literal-mindedness’ in autism. As you learned in Week 2, in everyday situations, people often say one thing while actually meaning or intending something else. For instance, when people speak ironically or sarcastically, understanding what they really mean depends on ‘reading behind’ what they say to their intentions given the context. To test how autistic people interpret non-literal utterances, Francesca Happé devised the ‘Strange stories’ test (Happé, 1994).

Participants in the test were presented with stories like this one which contains an example of irony:

The participants were asked:

• Question 1: Is it true what Ann’s mother says?

• Question 2: Why does Ann’s mother say this?

Figure 2 Ann and her mother.

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This cartoon drawing shows Ann's mother bringing food to Ann, who is watching TV and paying no attention to her mother.

Figure 2 Ann and her mother.

While autistic participants were able to identify that what Ann’s mother says is not true, most struggle to identify why she might say it, suggesting, for instance, that she was ‘having a joke’. A person who has difficulty in reading the meanings and intentions behind other people’s utterances may find all such expressions, interpreted literally, really puzzling or disconcerting. The consequences can sometimes be really profound.

In this extract, Wenn Lawson describes how, years ago when autism was less well known, his literal interpretation of questions from a psychiatrist led him to be misdiagnosed with schizophrenia (Lawson and Roth, 2011).

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WENN LAWSON

The doctor asked me a couple of questions – he asked me if I heard voices, which seemed like a really silly question because as far as I was concerned voices are actually designed to be heard and most of us, unless we are deaf, hear voices, so I said ‘yes’. He said ‘what do these voices say to you?’ and I said ‘well it depends on whose voice it is’. He said ‘do you hear more than one?’, and I said ‘yes I hear many’. He then asked me if I see things, which also was a strange question because I’m not blind, although I only have sight in one eye, so I said ‘yes I do see things’. So he concluded I lived detached from reality, and that I had auditory and visual hallucinations, which equates to being schizophrenic, so he said to my parents that their daughter was mentally ill, that she was schizophrenic, would need anti-psychotic medication, and in fact they put me into a psychiatric hospital.

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In Week 2 you viewed two video clips  titled ‘Socially awkward’ and 'Misunderstanding', which you might like to watch again, considering how ToM difficulties could affect the behaviour of the young man in the clip.

Just how ToM and language skills are linked is debatable (de Villiers, 2000). Autistic people with pronounced language problems are more likely to fail false belief tasks, possibly suggesting that language difficulties cause ToM difficulties rather than the other way round. With much greater awareness of literal-mindedness these days, organisations like the National Autistic Society advocate clear, straightforward language for communicating with people in the autistic community.

You will recall from Week 2 that ‘non-social’ features of autism include the tendency to repeat particular movements or activities, to be stuck with familiar routines and to be resistant to anything new or unfamiliar, however insignificant the change might seem to others. Here we look at two theories which focus on these traits.

Some experimental tests suggest that the profile just described reflects problems with executive function (Demetriou et al., 2017). This means the mental capacity to organise thoughts and actions to meet goals, for instance completing a task, shifting flexibly from one task to another, or thinking up new ideas for things to do. Executive function difficulties are not unique to autism – for instance, they occur in ADHD.One test of executive function in which children and adults with autism may have difficulty is the Tower of Hanoi puzzle, illustrated below.

Tower of Hanoi

The puzzle consists of three pegs, A, B and C, and a set of rings that vary in size. At the start of the test, the rings are arranged in order of size on peg A (see Figure 2). The aim is to move all the rings, one at a time and in as few moves as possible, to peg C, with the constraint that a larger ring can never be placed on top of a smaller ring. To succeed at this task the participant must work out an overall strategy or plan for transferring the rings – the secret is in the way all three pegs, including peg B, are used as ‘staging posts’.

Figure 3 The Tower of Hanoi puzzle.

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This 'before and after' type image first shows the puzzle in its 'initial state' with all the rings stacked on the first peg, then the 'goal state' after they have all been moved to the final peg, where they are stacked in the same order.

Figure 3 The Tower of Hanoi puzzle.

You might like to find an online version of the Tower of Hanoi puzzle (such as this one) and try it for yourself. (Note: neurotypical people as well as autistic people may find this task difficult. No conclusions can be drawn from finding the task challenging.)

Other executive function tasks test flexibility and the ability to generate new ideas.

Watch this video clip, in which Dr Jamie Craig asks first a child with autism, and then a typically developing child to suggest new uses for a piece of foam. You will notice that while both children come up with some ideas, the typically developing child offers a greater and richer range of suggestions (Craig and Baron-Cohen, 1999).

Download this video clip.Video player: aut_1_wk04_imagination_test.mp4

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MALE TEACHER:

What could this shape be? What does it look like?

CHILD:

Glass

NARRATOR:

In this experiment a boy with autistic spectrum disorder is asked to see the possibilities of a piece of foam.

MALE TEACHER:

What about this way? What could it be if it was this way?

CHILD:

A foot

MALE TEACHER:

A foot. Very well done. Thats right.

NARRATOR:

The same task is given to a typically developing child

MALE TEACHER:

Can you tell me lots of things this could be?

TYPICAL CHILD

A snake.

MALE TEACHER:

A snake. What else could it be?

TYPICAL CHILD:

A hat. A measuring board. A circle. Thats the shoe and thats the leg. That part can be a stem and that part can be a leaf.

ILONA ROTH:

Just producing fewer responses in some of these tasks is not necessarily a sign of impoverished imagination. It might be a deficit in what is called executive function, the ability to respond flexibly to situations. But in these tasks the responses were scored for both their quality and their quantity and the autistic children had difficulties with both of those.

MALE TEACHER:

It seems to be when you talk to people about imagination they expect something that steps out of ordinary just coming up with lots of answers. In terms of the imagery involved there seems to be a distinction between real world imagery and impossible or unreal imagery.

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Executive function difficulties may be one reason why even able autistic people can find everyday life challenging. Difficulties with everyday organisational tasks are well illustrated in this interview extract with Wenn Lawson (Lawson and Roth, 2011):

Download this audio clip.Audio player: aut_1_wk04_lawson_autism_and_family_life_clip.mp3

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WENN LAWSON

For example, I am no good at budgeting, I am not good with filling in forms, I am not good with paperwork, I am not good with money, I can do statistics but not numbers, which sounds a bit odd; but formulas are a lot easier to work with than everyday math. So I have family who take charge of those sort of things, and that frees me up just to focus in on my writing and lecturing and touring to talk in various ways about autism. If I didn’t have that, I'm not sure quite how I’d cope. I feel very strongly about Viktor Frankl’s understanding about meaning in life, and the meaning for me is sharing about what autism is. So I suppose that is how we separate the roles in our family. I adapt by accepting my limitations. It’s hard sometimes accepting that I am not very good at crossing roads. I've only been knocked over once this year so far, which isn’t bad. Even though I know academically about looking in all directions and listening while you cross the road, what tends to happen is that I get so focused on noticing that that truck has now gone, I forget again to look the way that the truck came from just to check there’s nothing else coming. Things like this I find quite difficult but I realise that I have these limitations. and so I tend not to travel alone and I have a lot of support.

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As you saw in Week 2, people on the autism spectrum often have a very good eye for detail, coupled with difficulty in ‘seeing the wood for the trees’, that is, in grasping the most salient aspects of a concept or idea. This thinking style is sometimes known as weak central coherence. Attention to visual detail has been studied with the embedded figures test, where the task is to find a simple shape such as a triangle, embedded in a larger figure. Some people on the autism spectrum find the embedded shape more easily and quickly than neurotypical people, suggesting that they are focusing on the details, not on the overall shape and identity of the figure (Happé and Booth, 2008).

Figure 4 Example of the embedded figures test. Can you pick out a shape within the pram figure that exactly matches the separate triangle?

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This is a simple line drawing of a pram, with many geometric shapes and lines drawn over it. There is a drawing of a triangle beside the pram. The test asks the person to find the matching triangle within the many shapes in the pram drawing.

Figure 4 Example of the embedded figures test. Can you pick out a shape within the pram figure that exactly matches the separate ...

This kind of visual eye for detail could be very useful in jobs such as quality control on a production line, where picking up subtle flaws in a product is crucial. Conversely, an autistic person may find it hard to work out what a whole object is from drawings of parts, or be unable to arrange apparently random sentences into a coherent story. This could, for instance, put a student at a disadvantage when trying to assemble information for an essay.

Weak central coherence could help to explain the narrow, specific focus of special interests and adherence to familiar routines in people with autism. Although changes to routines may seem minor and unimportant to a neurotypical person, for an autistic person, the feeling that everything is not exactly how they expect it and prefer it to be may provoke extreme anxiety.

Watch these video clips in which two autistic people describe their perfectionist tendencies.

Download this video clip.Video player: boc_aut_1_video_week4_surrey_autism_board_2.mp4

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MAN:

I'm constantly going out and looking and assessing things I need to do. I put a lot of pressure on myself, because I'm never happy cause there's always something to do. But most people are happy where they work. But they never switch off from that. And that's why I was out this morning, because I was annoyed a bed that wasn't weeded So I had to do it. And it's never ending gardening any way.

But yeah. I always go back and assess what I've done I'm very particular. Right now I'm just getting me hair cut. I'm as fussy as anything, getting me hair cut. It's got to be spot on. You know, everything's got to be spot on.

I'm like, I'm obsessed with-- everything's got to be immaculate and it its place.

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ANDRE JEAN-BAPTISTE:

I feel like some of the positive sides can be my motivation and my commitment. I can be very enthused. I can keep going back and doing things. In some cases, where other people may stop or get sick of it, I can have an extreme level of repetition that may enable me to get through or just to do certain tasks to a high level.

You know, maybe it's like I'm a bit of a perfectionist. You know, I like to sort of try and do things to a high quality, which is a double-edged sword. I mean, not all of the time. It can be good.

But in other cases, I'm just taking things too far, you know, there's no need for it. Or maybe it's just outside of my ability. It's hard for me to accept that there are things I can't do to a higher standard. That's what gets me, because I'm always trying to do it all, trying to do too much at times.

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Attention to detail by autistic people does not invariably show up in experimental tests. However, the theory does resonate with what a lot of autistic people experience, and also seeks to address strengths as well as challenges in the autistic thinking style. Next we will consider one more recent theory which aims to integrate some features of the approaches discussed so far.

As you have seen, the ToM approach primarily focuses on social challenges in autism, while executive function and weak central coherence focus primarily on non-social aspects. In the early 2000s, Baron-Cohen proposed a new theory which combined revised ideas about the social difficulties with a new approach to the non-social differences. This is known as the empathising–systemising theory.

One stimulus for Baron-Cohen's new approach was some research suggesting that autistic people may struggle to understand other people’s emotions or feelings. In one experimental test known as ‘Reading the Mind in the Eyes’, participants looked at images such as the one below, and had to choose which of the emotions mentioned was being portrayed (Baron-Cohen et al., 2001). Autistic adults had more difficulty than control participants, and often made the wrong choice.

Figure 5 Image from the ‘Reading the Mind in the Eyes’ test.

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This is a photograph showing somebody's eyes and eyebrows. Around the photograph are the words 'impatient', 'aghast', 'irritated' and 'reflective' for the participant to choose from.

Figure 5 Image from the ‘Reading the Mind in the Eyes’ test.

Bringing earlier ToM work together with research on emotion recognition, Baron-Cohen proposed that autistic people may have difficulty with empathising – recognising or understanding other people’s emotions, and reacting appropriately, leading to their difficulties in interacting with other people, making friends, and so on. At the same time, they may be strongly drawn to subject matter governed by systems or rules, leading to an interest in fields like physics, mathematics and technology, and in fact any domain which can be approached in a systematic rule-like way, which Baron-Cohen termed systemising (Baron-Cohen, 2009).

This quote from Luke Jackson, who wrote his own guide to Asperger syndrome when a teenager, illustrates a systemising approach in his fascination with chain reactions and springs.

To provide evidence for the ‘low empathising/high systemising profile’, Baron-Cohen devised questionnaires – the empathy quotient (EQ) and the systemising quotient (SQ). People were asked to evaluate how strongly they agreed or disagreed with statements such as ‘I find it easy to put myself in someone else's shoes’.

From people’s total questionnaire scores, Baron-Cohen reported that autistic respondents tended to score high on systemising and low on empathising, whereas few of the typically developed respondents tested showed the same pattern (Baron-Cohen et al., 2014). According to this profile, autistic people have particular interests and skills in ‘systematic’ subjects such as engineering, science and computing, and are less interested or skilled in dealing with people and social relationships. This profile does seem broadly consistent with the diagnostic criteria, and the theory has the merit of attempting to integrate social and non-social characteristics. However, the approach has been strongly questioned (Subbaraman, 2014). Firstly, since the questionnaires are ‘self-report’, participants may choose their answers to fit a certain self-image, rather than their true preferences. Secondly, the overall score differences between autistic and control groups of participants are small. Thirdly, the theory plays to a predominantly male stereotype of the autistic person as socially insensitive and obsessed with machines. But as you saw in Week 2, autistic people may have skills in many areas besides engineering, science and computing. They cannot be assumed to conform neatly to the empathising–systemising profile, and the way autism is expressed in women may be particularly far from this account.

Each of the psychological theories outlined this week is based on research, and offers possible insights into the thinking processes and experiences of individuals with autism. A serious limitation to all the theories is that the experimental evidence tends to come from ‘high-functioning’ individuals, who are able to understand and comply with task instructions. Even within this group, there are individual differences in the pattern of responses, highlighting once again the heterogeneity of autism. Also, autistic females are often under-represented in psychological tests, and when they are tested, there are some differences in how they respond (Mandy et al., 2012).

None of the approaches considered offers insights into unusual sensory responses, such as hyper- and hyposensitivity to sounds and other sensory stimuli. These affect a majority of people on the spectrum, but in different ways, which makes it hard for researchers to identify common underlying factors. Some recent research in this field focuses on differentiating the sensory issues in autism into different profiles, as a first step towards explaining underlying causes (Tomchek et al., 2018).

Psychological theories and tasks do provide a useful reference point for research into how underlying neurobiological differences relate to the behavioural characteristics of autism. We turn to neurobiology next.

Neurobiological research covers a range of levels from the structure and function of brain areas, to the way nerve cells communicate with one another, to the role of ‘chemical messengers’ such as hormones.

Research into the structure and function of the brain draws extensively on a range of brain imaging techniques. Magnetic Resonance Imaging (MRI) suggests that key brain structures may have a slightly different size or shape in autistic people. For instance, studies suggest that the brains of some young autistic children are 5–10% bigger than those of typically developing children, although this difference disappears by adolescence. Another area where increased size has been observed is the amygdala, a brain region involved in evaluating the emotional significance of external events. Overgrowth of the amygdala in children with autism is related to the severity of their social and communication difficulties, – greater overgrowth tends to go with more severe difficulties – but again this disparity of size compared with typical development disappears in adolescence.

Functional Magnetic Resonance Imaging (fMRI) monitors brain activity while a person is performing psychological tests, such as recognising faces, responding to emotional stimuli or understanding language.

Figure 6 Image of Functional Magnetic Resonance Imaging (fMRI) scanning. The participant in an fMRI study responds to images, sounds or other stimuli while lying in a scanner. Use of magnetic fields to monitor blood flow in the brain yields information about which brain regions are active.

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This photograph shows a person about to be scanned by an fMRI machine.

Figure 6 Image of Functional Magnetic Resonance Imaging (fMRI) scanning. The participant in an fMRI study responds to images, sounds or ...

The patterns of brain activity revealed by fMRI may differ in people with autism, compared to the neurotypical population. For instance, there may be reduced activity in a brain region called the fusiform gyrus, which has a specialised role in face recognition, linking with the observation that autistic people find it hard to recognise faces which they have seen before.

Figure 7 Images of fMRI scans of an adolescent male on the autism spectrum (right) compared with an age- and IQ-matched typically developing control (left).

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These two side-by-side fMRI images show the right and left cerebral cortex, and the cerebellum. The left image is a control, and the right image is from a subject with an autism spectrum diagnosis. Within the images, the fusiform gyrus is marked within a red circle. Red/yellow signal shows brain areas that are significantly more active during perception of faces; signals in blue show areas more active during perception of non-face objects. There is a lack of face activation in the autistic subject, but average levels of non-face object activation.

Figure 7 Images of fMRI scans of an adolescent male on the autism spectrum (right) compared with an age- and IQ-matched typically ...

Atypical patterns of brain activity are also observed when autistic people perform tasks such as the ‘Reading the Mind in the Eyes’ test illustrated earlier.

(See Lai, Lombardo and Baron-Cohen, 2013, for an overview of findings like those discussed in this section.)

Other brain studies focus at the level of nerve cells or neurons and other microscopic components of the nervous system. The millions of neurons which transmit messages within the brain and nervous system form a dense network of connected fibres. One current idea is that the overall pattern of this connectivity is different in the autistic brain, with some areas being unusually densely connected, and others sparsely connected (Wolff, 2012, cited in Hughes, 2012).

Figure 8 Different areas of the brain are profusely connected by complex networks of neurons. The pattern of connectivity may be different in autism.

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This is an image giving an idea of the neuron network within the brain, which is speculated to vary structurally in the autistic brain.

Figure 8 Different areas of the brain are profusely connected by complex networks of neurons. The pattern of connectivity may be ...

There is also some evidence that the structure and functioning of synapses (the miniscule gaps between neurons) differs in autism. Messages are transmitted along nerve fibres by minute electric currents, but crossing the synaptic gaps involves chemical messengers called neurotransmitters.

Figure 9 Schematic image of a synapse with molecules of neurotransmitter carrying messages across the synaptic gap.

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This is a schematic image of a synapse with molecules of neurotransmitter carrying messages across the synaptic gap.

Figure 9 Schematic image of a synapse with molecules of neurotransmitter carrying messages across the synaptic gap.

Some studies suggest that some autistic people have higher than normal levels of a neurotransmitter called serotonin in their blood, suggesting an overproduction within the brain. Medical drugs which are known to influence serotonin uptake in the brain can have an impact on anger and repetitive behaviour in autism.

Finally, different levels of certain hormones have been reported. Hormones are another type of chemical messenger, which play an important role in bodily and brain function. For instance, when you experience a stressful situation, adrenaline is released which causes perspiration, raised heart rate and other ‘fight or flight’ reactions. Oxytocin is a hormone which is known to be important in social relations, and some studies report lower levels in children with autism. Some studies suggest that administering extra oxytocin to autistic people via a nasal spray may help with emotion recognition skills.

If you are interested to learn more about the brain and nervous system and how they are implicated in autism, you may like to look at parts of this optional interactive activity:

You can find an downloadable interactive brain activity at this link.

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Both the psychological characteristics of autism and underlying neurobiological atypicalities are thought to be linked to genetic influences.

As you learned in Week 1, twin studies provide evidence for a strong genetic factor in autism. When one twin of a pair is on the autism spectrum, the chance of the other twin also being on the spectrum (known as concordance) is much higher if these twins are identical than if they are fraternal. Identical twins have identical genes, whereas fraternal twins are no more alike genetically than, say, two brothers or two sisters. Identical twins and fraternal twins are likely to be very similar in their experiences of the environment. Therefore, the higher concordance for autism in identical twins suggests that the predisposition to develop autism is strongly genetic.

Even in non-identical twins or in siblings, concordance for autism is higher than in the neurotypical population. Twin and sibling concordance findings together suggest that autism can be passed down (inherited) from one generation to another, and affect multiple members of the same family. This was illustrated in video clips in Week 3: brothers Acis and Harry  and their grandfather John are all on the autism spectrum.

Genes are commonly referred to as the ‘blueprints’ for life – the basic units of heredity, which means the passing on of physical and behavioural traits from one generation to the next. Differences in, for example, our eye colour or hair structure are due to differences in genes we inherit from our parents. Genes are small sections of very long molecular structures called deoxyribonucleic acid (DNA). DNA has a precise sequence of units, with a section of these units together constituting a gene.

Each gene contains the instructions for making a specific protein which in turn instructs our cells and tissues how to interact, grow or respond to damage and diseases. For example, there is a gene containing instructions for making the hormone insulin, a substance with an important role in regulating our blood sugar level. While we each have a gene that codes for insulin, the precise sequence of units within that gene can vary between individuals. Such differences, known as DNA variants, may cause differences in the way a protein functions

Genes are organised into 23 distinctive pairs of structures called chromosomes, carried within the cells of our body, and visible down a microscope (Fig. 10). Of each pair of chromosomes, one is inherited from the mother and one is inherited from the father. The first 22 pairs of chromosomes look the same down the microscope for men and women. The last pair are the sex chromosomes. The body cells of males have one copy each of the X chromosome and the (much smaller) Y chromosome, while the cells of females typically have two X chromosomes.

Figure 10 Photograph of the 23 pairs of chromosomes of a human male, from a light microscope image, magnified approximately 1000 times.

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This is a light microscope image magnified approximately 1000 times, showing the 23 pairs of chromosomes of a human male. The first 22 pairs of chromosomes look the same down the microscope for men and women. The last pair are the sex chromosomes. The body cells of males have one copy each of the X chromosome and the (much smaller) Y chromosome, while the cells of females typically have two X chromosomes.

Figure 10 Photograph of the 23 pairs of chromosomes of a human male, from a light microscope image, magnified approximately 1000 times. ...

In humans, the 23 chromosome pairs hold tens of thousands of genes that together are known as the human genome.

Each of us inherits one member of each chromosome pair from each of our parents – but before they are passed on during sexual reproduction, material within each of these chromosome pairs crosses over during the formation of egg or sperm, part of a process known as meiosis (Fig. 11). Natural breakages occur on each paired chromosome, shown here at the white line two thirds of the way down, and a section of genetic material is exchanged such that novel combinations are formed. Each egg or sperm inherits just one of these paired chromosomes which includes a novel combination of material from each parental chromosome.

Figure 11 A chromosome pair before, during and after the cross-over of genetic material that occurs during production of eggs and sperm.

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This diagram shows a chromosome pair before, during and after the cross-over of genetic material that occurs during production of eggs and sperm. The diagram shows three stages. In the first stage, a label reads 'pair of homologous chromosomes' – to tell them apart, one chromosome is coloured in red, the other is coloured in blue. Stage two, labelled 'breakage occurs during meiosis' shows the same chromosomes, both of which now have a white line crossing them two thirds of the way down, indicating natural breakages. This leads to the third stage which is labelled 'rejoining to the other member of the pair', and shows that the chromosomes have exchanged genetic material at the natural breakage points, such that novel combinations are formed (i.e. both are now a mix of red and blue material).

Figure 11 A chromosome pair before, during and after the cross-over of genetic material that occurs during production of eggs and sperm.

The result is that offspring inherit combinations of each of their parents' chromosomes, and can therefore also exhibit characteristics of each parent, and of earlier generations (Fig. 12).

Figure 12 The effect of crossing over on the arrangement of genetic material along chromosomes, shown across three generations. The three colours represent the different origins of the genetic material in the chromosomes of the grandparents, and how a grandchild thus inherits a mix of genetic material from both grandparents.

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This diagram shows the effect of crossing over on the arrangement of genetic material along chromosomes, shown across three generations. At the top of the diagram, two pairs of chromosomes are shown. The first pair is labelled 'grandmother' and these are coloured in yellow and red. The second pair is labelled 'grandfather' and these are white and blue. An arrow indicates these chromosomes are passed down to the next generation. A pair of chromosomes labelled 'mother' show that natural breakages have passed down a mix of genetic material from the grandparents. As a result, one of the mother's chromosomes is coloured in a mix of yellow and red, and the other is a mix of blue and white. The third generation labelled 'child' then shows one chromosome, inherited from the mother. It is a mix of all four colours from the grandparental chromosomes, thus showing how a grandchild inherits a mix of genetic material from both grandparents.

Figure 12 The effect of crossing over on the arrangement of genetic material along chromosomes, shown across three generations. The three...

During egg and sperm formation, and during breakage and rejoining of the parental chromosomes, additional changes to the genetic sequence may occur. Such ‘mutations’ give rise to new DNA variants which may contain altered instructions for protein development. This may in turn trigger differences in the way the brain and nervous system develop, which are then passed on to further generations

In autism, links are proposed between particular genetic variants, atypical development of the nervous system including the brain, and behavioural differences such as theory of mind difficulty and repetitive tendencies.

However, this is a complex and speculative field. Whereas certain conditions (e.g. cystic fibrosis) result from mutation of just a single gene, autism (except in fairly rare cases) involves the combined effects of variants in many different genes – it is said to be polygenic. Also, this combination of genes and variants may vary from one person or family to another, so autism is said to be heterogeneous. Researchers have found candidate genes (genes that may potentially transmit susceptibility to autism) on a very large number of chromosomes.

Besides this complex pattern of genetic influences, the heritability of autism (the extent to which it can be attributed to genetic factors) is not 100%. A parent may be on the autism spectrum without his or her children inevitably having autism. A child may develop autism without a family history – their genome may be altered by a new mutation, for instance arising during egg or sperm production, or by epigenetic influences, which control the action of certain genes. Other non-genetic factors may also influence the development of autism. For instance, exposure in the womb to Valproate, taken by a mother as epilepsy medication, may increase a child’s risk of developing autism (Christensen et al., 2013). Influences such as these, thought to affect the prenatal environment of the developing foetus, are not well understood at present.

(See Lai, Lombardo and Baron-Cohen, 2013 for an overview of autism findings like those discussed in this section)

Now it’s time to complete the Week 4 badge quiz. It is similar to previous quizzes, but this time instead of answering 5 questions there will be 15.

Remember, this quiz counts towards your badge. If you’re not successful the first time, you can attempt the quiz again in 24 hours.

Week 4 badge quiz.

Open the quiz in a new window or tab then come back here when you’re done.

This week has looked at key explanations of autism at three different levels: psychology, neurobiology and genetics. Psychological research has highlighted processes (theory of mind, executive function, etc.) which may help to explain observed behaviour and thinking style in autism. But no theory is conclusive, the findings vary, and in particular sensory differences have proved difficult to explain. There is copious research into brain and nervous system differences and genetic influences related to autism, but again, no firm conclusions can be drawn.

Next week deals with the very different question of how autistic people can be helped.

You should now be able to:

• understand key approaches to explaining autism
• differentiate three levels of explanation: psychological, neurobiological and genetic
• understand key psychological accounts of the autistic ‘thinking style’ and identify implications for everyday life
• appreciate key ideas about brain and nervous system function in autism
• appreciate the complex role of genetic influences in autism.

Now you can go to Week 5.