Gordon Fishell and his colleagues suspect that abnormal development of cortical interneurons — specialized nerve cells that relay signals from sensory neurons to motor neurons — is involved in this imbalance. The researchers are attempting to understand how specific subclasses of cortical interneurons develop and how they are integrated into cortical networks. To explore whether abnormal cortical interneuron development is an immediate cause of autism, Fishell and colleagues are building a profile of the genes expressed in this cell population in mice. Fishell's team is also using a new fluorescent labeling technique to map specific subclasses of cortical interneurons and their connections, combined with measurements of electric signal strength, to examine how disruptions in autism-linked genes can affect cortical networks in mouse models of autism. The researchers hope that this multi-pronged approach will allow them to identify direct links between autism-linked genes and malfunctions in cortical microcircuits.