PTEN and microcephaly: Supporting the former possibility is the evidence that PI3K/AKT/mTOR inhibition and GSK3 activation are associated with decreased neuronal cell survival [25, 26] and that, while the ablation of AKT3 and overexpression of PTEN are associated with microcephaly (small brains) [27], high AKT3 activity and inactivating mutations of PTEN are associated with macrocephaly (large brains) and autism-like behaviors [23, 24].