“no great genius was without a mixture of insanity”
“They say madness runs in our family. Some even call me mad! And why? Because I dared to dream …of my own race of atomic monsters! Atomic supermen with octagonal-shaped bodies that suck blood out of…”
-Prof. Hubert Farnsworth
To be clear, by genius I mean the ability for humans to think at the level we do. And by madness, I mean madness. A recent study suggests that we have our big brains at a high price: schizophrenia. It comes down to the massive metabolism needs that our brains have. A team led by evolutionary biologist Philipp Khaitovich of the Shanghai Institutes for Biological Sciences and the Max Planck Institute for Evolutionary Anthropology created an experiment to see how much genes that are involved in schizophrenia have evolved since humans split from chimpanzees.
First, the researchers looked at published databases of positively selected brain genes, which have been classified into 22 categories according to their function. They found that six of the categories included a high proportion of genes also implicated in schizophrenia; the genes in these six categories relate to energy metabolism.
So the team focused its search on energy pathways in the brain. Using a technique called nuclear magnetic resonance spectroscopy, the researchers measured the concentrations of 21 metabolites key to nerve function in the brains of 10 deceased schizophrenia patients and 12 normal human controls. Specifically, they examined an area of the prefrontal cortex implicated in social cognition. Nine of the metabolites, such as lactate, choline, and acetate, showed significantly different concentrations–some higher, some lower–in schizophrenics and normal humans. That finding, the authors say, confirms previous studies that brain metabolism is “substantially altered” in schizophrenia.
The researchers then looked at whether those nine metabolites might be important in human brain evolution. When they measured the concentrations in the same area in chimp brains, the team found that the differences between chimps and normal humans were much greater for those nine than for the 12 metabolites not implicated in schizophrenia, suggesting that energy pathways implicated in schizophrenia were also altered by human evolution, the team reports this week in Genome Biology. And 40 genes involved in these nine schizophrenia-related pathways also differed much more between chimps and humans than genes associated with the other 12.