At ages 2 and 4, autistic toddlers are more likely to have an abnormality of the amygdala, a part of the brain associated with facial recognition and emotion.  This enlargement of the amygdala is in keeping with previous studies that suggest autistic children’s heads grow in circumference faster than children without the disorder.

Researchers at the University of North Carolina at Chapel Hill, led by Matthew W. Mosconi, used magnetic resonance imaging (MRI) to chart the brains of 50 children diagnosed with autism spectrum disorder (ASD) and 33 children who did not have the disorder.  Each child was tested at age 2 and again at age 4.

One part of the study was a measure for joint attention, or the child’s ability to follow a second person’s gaze.  Measuring joint attention reveals how effectively the child initiates an experience shared with another, behavior thought to be an early developmental step toward later language and social functionality.

The research team found the amygdala enlargement in autistic children at age 2, suggesting growth for this area of the brain becomes accelerated before age 2 and remains so throughout early childhood, as evidenced by continued amygdala enlargement at age 4.

The current issue of the Archives of General Psychiatry carries full details of the study.