“Signs of autism can be detected in six-month-old babies by measuring brain activity,” the Daily Mail has reported. While the Mail was correct, the research has not yet proved to be a perfect diagnostic test.
This and other related headlines are based on a study that assessed the brain activity of 104 infants aged 6-10 months as they watched an image of an adult’s face whose eyes moved from looking away from them, to directly at the infant, then away again. Researchers called these eye movements ‘dynamic eye-gaze shifts’. They then assessed whether differences in brain activity in response to the eye-gaze shifts were related to autism developing in the same children at three years.
Children who did not develop autism showed large spikes in brain activity when they saw the ‘gaze shifts’. Much smaller spikes in brain activity were detected in the infants who went on to develop autism, raising the prospect that autism could be identified earlier than is currently clinically possible.
However, this test was not 100% accurate. Some babies showing low brain activity spikes did not go on to develop autism and vice versa. As the groups overlap, there cannot be a simple and useful cut-off value to predict autism.
Developing and refining this type of test into something that can be routinely used to detect autism in infants is likely to take some time and will certainly require more research on larger groups of infants with autism and unselected healthy infants too.
Where did the story come from?
The study was carried out by a collaboration of researchers from English, Canadian and Australian universities and was funded by the UK Medical Research Council. It was published in the peer-reviewed science journal Current Biology.
The media reporting of this story was generally well balanced. Many stories included quotes from the study authors that a definitive test would take time to develop and that the current assessment is not 100% effective.
What kind of research was this?
This study was a prospective longitudinal study investigating whether the brain function of infants aged 6-10 months differed in response to viewing faces that changed the direction of their gaze. The researchers then looked at whether these brain function differences could predict a diagnosis of autism at three years of age.
The authors report that there are currently no reliable methods of predicting autism in infants younger than about two years of age. Current diagnosis relies on the detection of behavioural symptoms of autism that typically develop in a child’s second or third year. Behaviours associated with autism include impairments in social skills and communication, and the presence of rigid, stereotyped and repetitive behaviours.
The authors say previous research shows typical infants’ sensitivity to eye gaze in the first year of life predicts a range of social and communication skills that emerge later. Detecting autism at an early age could potentially lead to ways of better supporting the child during early development, improving their wellbeing and life chances.
What did the research involve?
The researcher recruited a group of 104 infants - 54 at risk of autism because of a family history of the condition and 50 controls, with no family history of autism. The infants were followed from 6-10 months through to three years of age.
The researchers measured the 6 to 10-month-old infants’ response to changing images of faces. They did this by recording event-related potentials (ERPs), which are a measure of brain electrical activity in response to a thought or perception. In this study, ERPs were used to measure the perception of a face changing between looking directly at the infant and then away from them. The researchers called this ‘dynamic gaze-shift stimuli’.
The researchers also tracked the eyes of the infants to examine the amount of time they spent looking at the eye region of the faces they were shown. This allowed the researchers to assess whether different responses to the eye gaze were due to differences in attention to the eye region or whether brain functions were more important.
The researchers reported that dynamic gaze-shift stimuli are more likely to engage wider social brain mechanisms than static images as they mimic a real social interaction more closely. However, researchers compared their dynamic gaze results with that from ‘static gaze’, (images of a face whose eyes were looking at, or away from, the infant) to see how they compared to each other.
The brain activity levels of infants at risk of autism were contrasted with the controls. The researchers then looked at how the brain function differences at 6-10 months related to a later diagnosis of autism. An independent team assessed whether the infants had autism at two and three years old.
What were the basic results?
The brain activity of the control group showed large spikes of activity in response to eye gaze changes when the face image held a gaze toward, compared to away from, the infant. The brain activity spikes of infants at risk of autism were significantly smaller in response to the same stimulus.
The differences in brain activity of the control group verse at risk group were not restricted to the dynamic gaze results. Similar results were seen when static images were used.
The researchers found that those who did not go on to develop autism at three years of age showed large spikes in brain activity relating to the changes in eye gaze at 6-10 months. Crucially, those that did develop autism showed significantly smaller spikes in brain activity. The static image test did not predict a later diagnosis of autism.
Eye tracking information was available for 93 of the 104 infants. There was no difference in the time at-risk infants and control infants spent looking at the faces’ eyes relative to other areas of the face.
How did the researchers interpret the results?
The authors conclude that ‘brain function measures can successfully differentiate groups of infants at risk [of autism] from low-risk control within the ﬁrst year of life'. They go on to say that ‘response to dynamic gaze shifts during the first year of life distinguished the group of infants who later develop autism’.
This small study highlights a potential method of identifying children who are likely to develop autism at 6-11 months, much earlier than the current method of diagnosis. The authors suggest this could potentially pave the way for more selective targeting of early intervention efforts and procedures to these children, increasing their life chances.
While this study provides intriguing results it is important to bear in mind some practical limitations. For instance, while the average differences between the brain function of the infants that went on to develop autism compared to those that did not were significantly different, individual values from the two groups did overlap. This means that there is probably no useful clinical cut-off value to predict autism. Similarly, the researchers do not describe how the controls were selected or report how good the test was at diagnosing autism, known as the ‘test sensitivity’. Reporting these key results would have helped us better assess the accuracy and importance of these findings.
Much larger studies would be needed to establish a suitable brain activity level to use to identify as child as 'likely to develop autism'. These studies could better assess the natural variation in brain activity from a large group of infants. Similarly, it is unlikely a future autism assessment would rely on a single test, such as dynamic eye gaze, but would instead use a combination of tests.
The uncertainty about what cut-off values to use, and the drawbacks of using a single predictive test, makes the development of an early identification test more complex. It may be some time before a predictive test is routinely available to identify infants likely to develop autism earlier than is currently possible.