WASHINGTON: Examining the human brain at the cellular level in more detail than ever before, scientists have identified an enormous array of cell types - more than 3,300 - populating our most complex organ, creating an atlas that may help pinpoint the cellular basis of neurological diseases and facilitate new therapeutics.
The ambitious research unveiled on Thursday also examined similarities and differences between the brains of people and other primates — chimpanzees, gorillas, rhesus monkeys and marmosets — illuminating some of the factors that separate us from our evolutionary kin and truly make us human.
The work, presented in 21 studies published in Science and two other journals, was backed by the US government's National Institutes of Health BRAIN Initiative Cell Census Network consortium.
The human brain is complex in terms of its utility — sensing, moving, reading, writing, speaking, thinking and more — and its cellular diversity.
Neurons — or nerve cells — are the brain's fundamental units, taking in sensory input, transmitting commands to the muscles and imparting electrical signals along the way. The brain comprises almost 100 billion neurons and even more non-neuronal cells. These all are organised in the hundreds of distinct brain structures that govern a spectrum of functions.
The research identified 3,313 cell types, roughly 10 times more than previously known, and the complete set of genes used by each cell type while also mapping their regional distribution in the brain.
"The brain cell atlas as a whole provides the cellular substrate for everything that we can do as human beings," said neuroscientist Ed Lein of the Seattle-based Allen Institute for Brain Science, one of the researchers.
The various cell types have distinct properties and are likely affected differently in disease, Lein said.
One surprise was that the cellular diversity was concentrated in evolutionarily older parts of the brain - the midbrain and hindbrain - instead of the neocortex, responsible for higher cognitive functions including learning, decision-making, sensory perception, memory and language.
Brain-related diseases such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis (ALS) are among the most intractable.
"Most brain diseases still have no cures or even treatments, and this atlas should serve as a baseline to accelerate progress in understanding the detailed cellular basis of disease and targeting the next generations of therapeutics," Lein said. — AFP
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