Eye contact avoidance is a common feature of autism. This week I am reviewing a new study that, for the first time, looks at the relationship between the amount of eye contact and levels of brain activity in important regions previously implicated in autism spectrum disorders. The results may help explain why autistic individuals avoid looking at faces, and how this could be leading to some of their difficulties with facial perception.
Individuals with an autism spectrum disorder (ASD) often have difficulty processing facial identities and expressions. Therefore, many studies in ASD have focused on determining whether the brain areas involved in face processing are functioning correctly. Some of these experiments have shown that one of these face processing areas (the "fusiform gyrus") is under-activated when autistic individuals are asked to look at faces. This has lead to a hypothesis that defects in face-processing are due to the inability of this brain region to become activated. A new study published this week in Nature Neuroscience has shown that the fusiform gyrus can be activated in autistic individuals and that the under-activity may simply be because autistic individuals do not spend as much time looking at faces as typically-developing people.
In this new study by Dr. Richard Davidson and colleagues at the University of Wisconsin, individuals with ASD and typically-developing controls were asked to perform two different facial processing tasks (e.g., to decide whether or not a face is emotional or whether or not it is familiar). The researchers measured brain activity during these tasks, as well as the amount of time the individuals actually focused on the eyes of the presented faces. Within the ASD group, they found large variability in the total length of time each individual actually looked at the faces. The researchers discovered that the amount of time a subject spent focusing on the eyes was directly linked to the level of activation in the fusiform gyrus. In other words, the longer someone looked at a face, the more the face-processing regions were activated. Therefore, the defect may not be in the face processing regions themselves, but rather in the amount of time ASD individuals fixate on the eyes of the faces.
The researchers also propose an explanation for why ASD individuals avoid gazing at faces. In examining other patterns of brain activity during the facial discrimination tasks, they found that a structure called the "amygdala" was actually over-activated in ASD individuals. This is important because the amygdala is believed to be involved in generating heightened emotional responses such as fear and anxiety. Moreover, similar to what they found with the fusiform gyrus, in the autistic individuals the amount of activation of the amygdala was strongly related to the amount of time spent looking directly at the faces.
This new paper is illuminating because it offers a theory as to why autistic individuals have difficulties with facial recognition. The authors propose that the cause may be an unusual emotional sensitivity to looking at faces, causing them to avoid eye contact, which in turn leads to the irregular activation of face processing regions. This is a very testable theory, and indicates that further study of the development of the amygdala circuitry is warranted. While this study doesn't rule out that possibility that is also some dysfunction in the face processing areas, it definitely offers the hope that developing targeted interventions to assist autistic individuals in overcoming their avoidance of eye contact may help them improve recognition of faces and emotional expression. This year CAN announced a Pilot Project grant to Dr. Ralph Adolphs from the California Institute of Technology for an in-depth analysis of the eye movements people with autism use to process faces. He will also test whether instructing them how to view faces can increase their ability to distinguish emotion. Recognizing familiar people and being able to read subtle facial expressions are critical components of social interaction, and treatment in this area would address one of autism's core deficits and provide the opportunity for pivotal changes in socialization.
Article citation: Dalton KM et al., (2005) Gaze fixation and the neural circuitry of face processing in autism. Nature Neuroscience 8, 519-526.