A German research team has found a link between happiness and the size of the brain, according to a study published in the recent issue of the journal Neurons.
Researchers from the Max Planck Institute of Molecular Cell Biology and the University Hospital Carl Gustav Carus Dresden, found a novel role of the happiness neurotransmitter serotonin. In addition to functioning in the brain to mediate satisfaction, self-confidence and optimism, the neurotransmitter acts like a growth factor for basal progenitors in the neocortex, and significantly contributes to its expansion.
In previous research, the team led by Wieland Huttner at the Max Planck Institute of Molecular Cell Biology, investigated the cause of the evolutionary expansion of the human neocortex, but in the recent study, the researchers focused on the role of serotonin in this process.
Serotonin is often called the happiness neurotransmitter because it transmits messages between nerve cells that contribute to well-being and happiness. However, a potential role of such neurotransmitters during brain development has not yet been explored in detail.
In the developing embryo, the placenta produces serotonin, which then reaches the brain via the blood circulation. Yet, the function of this placenta-derived serotonin in the developing brain has been unknown. In the new study, the researchers discovered that serotonin needs to bind to a receptor called HTR2A in order to activate downstream signaling. They tried to know whether this receptor could be one of the keys to the question of why humans have a bigger brain.
To explore this, the researchers induced the production of the HTR2A receptor in embryonic mouse neocortex. They found that serotonin, by activating this receptor, caused a chain of reactions that resulted in the production of more basal progenitors in the developing brain. More basal progenitors can then increase the production of cortical neurons, which paves the way to a bigger brain.
"There is evidence that supports the findings of our study. 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 malfunctions of serotonin and may suggest novel approaches for therapeutic avenue," summarized co-author Lei Xing in a report on Saturday.