Nonetheless, loss of 5-HTT, prenatal SSRI exposure and autism may be interconnected by both showing a reduction in callosal-dependent intercortical connectivity, which—together with the finding of Witteveen et al. (2013) that callosal projection neurons seem to be altered in 5-HTT knockout rats—raise the possibility that serotonin affects the identity of projection neurons. This evidence concerns the gene SLC6A4 and autism.