During development, neurons produced at a similar time from progenitor cells migrate and occupy similar positions in the cerebral cortex. They are layered horizontally, and then connect vertically into columns. In this way, neurons that transmit excitatory messages connect with those that transmit inhibitory messages, forming local communication networks. In children with autism, these neural columns are more narrow and dense than in normally developing children. The researchers hypothesize that these abnormalities are linked to autism, possibly due to an imbalance between excitatory and inhibitory neurons, or to impairments in their connections. They will explore this hypothesis in mice with Fragile X syndrome (a genetically caused form of autism). Using two-photon cellular imaging, they will follow migrating neurons into the cerebral cortex, and map their connections using electrophysiology recordings. What this means for people with autism: This study may reveal how abnormal cortical excitation or inhibition is linked to autism, and lead to improved treatment.