The neocortex enables us to speak, dream and think. In search of the causes underlying neocortex expansion, researchers at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, together with colleagues at the University Hospital Carl Gustav Carus Dresden, previously identified a number of molecular players. These players typically act cell-intrinsically in the so-called basal progenitors, the stem cells in the developing neocortex with a pivotal role in its expansion.
The researchers now report an additional, novel role of the happiness neurotransmitter serotonin which is known to function in the brain to mediate satisfaction, self-confidence and optimism—to act cell-extrinsically as a growth factor for basal progenitors in the developing human, but not mouse, neocortex. Due to this new function, placenta-derived serotonin likely contributed to the evolutionary expansion of the human neocortex.
“Abnormal signaling of serotonin and a disturbed expression or mutation of its receptor HTR2A have been observed in various neurodevelopmental and psychiatric disorders, such as Down syndrome, attention deficit hyperactivity disorder and autism. Our findings may help explain how malfunctions of serotonin and its receptor during fetal brain development can lead to congenital disorders and may suggest novel approaches for therapeutic avenues,” [said study supervisor Wieland Huttner.]