An autism diagnosis is based on behavior. But identifying a brain signature for the condition could help support diagnosis and even provide an early biomarker of the condition.

Knowing autism’s imprints in the brain may also shed light on biological mechanisms and point to targets for treatments. These imprints may be structural features or patterns of brain activity. Researchers can visualize both using magnetic resonance imaging (MRI).

But despite the decades of work, no one has found a characteristic brain structure or pattern of brain activity unique to autism. Brain imaging studies have turned up conflicting results, and few findings have been replicated. We asked five brain-imaging experts what they make of the lack of a solid result in this area. Is there a brain signature unique to autism, and if so, how might researchers find it? Here are their responses.