Individuals with autism spectrum disorder (ASD) often have difficulty looking others in the eyes. This is typically interpreted as a sign of social and personal indifference, but self-reports from people with autism suggests otherwise. Many say that looking others in the eye is uncomfortable or stressful for them; some will even tell you “it burns.” All of which points to a neurological cause.
Now, a team of investigators based at the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital has shed light on the brain mechanisms involved in this behavior. They reported their findings in a Nature Scientific Reports paper published online this month.
“The findings demonstrate that the apparent lack of interpersonal interest in autism is not, contrary to what has been thought, due to a lack of concern,” said Nouchine Hadjikhani, MD, PhD, director of neurolimbic research in the Martinos Center and corresponding author of the new study. “Rather, they show that this behavior is a way to decrease an unpleasant over-arousal stemming from overactivation in a particular part of the brain.”
The key to the research is the subcortical system in the brain. This system allows orientation toward faces in newborns and later is important for emotion perception. It is also specifically activated by eye contact. Previous work by Hadjikhani and colleagues revealed that the subcortical system was oversensitive to direct gaze and emotional expression in autism. In the present study, she wanted to take this further. She wanted to see what happens when subjects’ gazes are constrained to the eye-region—that is, when they are compelled to look people in the eyes—while viewing images of faces conveying different emotions.
Using functional magnetic resonance imaging (fMRI), she and colleagues measured differences in activation in the components of the subcortical face processing system—superior colliculus, pulvinar nucleus of the thalamus, and amygdala—in people with autism and in control subjects as they viewed faces either freely or with their focus constrained to the eye-region. They found that, while the two groups exhibited similar activation during free viewing, those with autism showed overactivation when they were compelled to concentrate on the eye-region. This was especially true with fearful faces, though effects were also observed with happy, angry and neutral faces.
The findings of the study support the hypothesis of an excitatory/inhibitory imbalance in autism (excitatory refers to neurotransmitters that stimulate the brain while inhibitory refers to those that calm it and provide equilibrium). Such an imbalance, likely the result of diverse genetic and/perinatal causes, can serve to strengthen excitatory synapses in the subcortical circuitry involved in face perception. This in turn can result in an abnormal reaction to eye contact, an aversive response to direct gaze, and consequently abnormal development of the social brain.
In elucidating the underlying reasons for eye-avoidance, the study also suggests more effective means of engaging individuals with autism. “The findings indicate that forcing children with autism to look into the eyes in behavioral therapy may create a lot of anxiety for them,” Hadjikhani said, “and that one should consider an approach in which a slow habituation to eye-contact may help them overcome this over-reaction. This could allow them to be able to handle eye contact in the long run, thereby avoiding the cascading effects that this eye-avoidance has on the development of the social brain.”
The researchers are already planning to follow up the research. Hadjikhani is now seeking funding for a study that will use magnetoencephalography (MEG) together with eye-tracking and other behavioral tests to probe more deeply the relationship between the subcortical system and difficulty with making eye contact in autism.
The co-authors of the Nature Scientific Reports study are Nicole R. Zürcher, Amandine Lassalle and Noreen Ward of the MGH Martinos Center; Jakob Åsberg Johnels, Eva Billstedt and Christopher Gillberg of Gothenburg University, Gothenburg, Sweden; Quentin Guillon of the Lyon Neuroscience Research Center, Lyon, France; Loyse Hippolyte of the University of Lausanne, Lausanne, France; and Eric Lemonnier of CRA, of Limoges, France.