Why are human neurons different from those of other mammals?

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A group of researchers has discovered that human neurons have significantly fewer ion channels than other mammalian neurons.

The lower density of ion channels may contribute to the more efficient brain function in humans.

The neuroscientists’ findings pave the way for future research into the evolutionary forces behind this distinction.

NeuronsTrusted Source are the building blocks of the central nervous system, which includes the brain and spinal cord. They share information via electrical impulses and chemical signals.

The human brain contains about 100 billionTrusted Source of these cells.
Neuronal impulses are generated by the activity of ion channels, which control the movement of mineral ions, including potassium and sodium.

Typically in mammalian brains, as the size of neurons increases, the density of the ion channels in the neurons also increases.

To the surprise of neuroscientists from the Massachusetts Institute of Technology, in Cambridge, and Harvard Medical School, in Boston, this was not the case for human neurons.

Lou Beaulieu-Laroche, Ph.D., a neuroscientist and the study’s lead author, explained in a recent LinkedIn post: “These findings have important implications for understanding our outstanding cognitive abilities and the challenges [that] therapies derived from animal models face in human clinical trials.”

Dr. Beaulieu-Laroche calls this paper his “highest scientific achievement.”
Neuronal size determines neuronal input-outputTrusted Source features — how likely a neuron is to “fire” following a certain level of input from other neurons. The size of neurons also varies widely across mammalian species.

The team of researchers analyzed brain samples from people with epilepsy who had undergone neurosurgical treatment, Etruscan shrews, mice, rabbits, and macaques, among other mammals.

The researchers aimed to “characterize layer 5 cortical pyramidal neuronsTrusted Source across 10 mammalian species to identify the allometric relationships that govern how neuronal biophysics change with cell size.”

The authors chose this population of neurons because they are “reliably identifiable,” and scientists have studied them extensively.

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