Alpha asymmetry in infants at risk for autism spectrum disorders.

Gabard-Durnam et al. (2015) placed tiny sensors on babies’ heads. They recorded brain waves while the babies rested.

The team compared two groups: infants with an older sibling with autism (high risk) and infants with no family history (low risk). They looked at a brain pattern called alpha asymmetry at 6 months and again at 12 months.

High-risk and low-risk babies showed opposite patterns of alpha asymmetry at 6 months. Their brain-wave paths also moved in opposite directions between 6 and 12 months.

These early brain differences appeared before any autism behaviors could be seen.

Bao et al. (2017) used the same high-risk baby design. They found that 3-month-old girls at risk did not tune out repeated speech sounds. Both studies show that brain markers can flag risk before behavior does.

Liu et al. (2024) extended the timeline. They showed that gesture problems between 12 and 16 months also predict later autism. Together, the papers build a chain: brain signs at 6 months, gesture signs at 12 months.

Lemcke et al. (2013) seems to disagree. They found that parent reports at 6 months were too weak to predict autism. The difference is the method: parent answers versus direct brain recording. EEG picks up silent biology that parents cannot see.

You now have a 6-month EEG marker that can sit in your early-detection toolkit. Pair it with later gesture checks and sensory screens for a fuller picture. If you work with baby siblings of children with autism, ask your assessment team about adding a quick EEG asymmetry scan at the 6-month visit.