Brain size not linked to Microcephalin and ASPM?. Normal Variants of Microcephalin and ASPM Do Not Account for Brain Size Variability: Normal human brain volume is heritable. The genes responsible for variation in brain volume are not known. Microcephalin (MCPH1) and ASPM (abnormal spindle-like microcephaly associated) have been proposed as candidate genes since mutations in … Continue reading Microcephalin & ASPM