There is a strange difference between the human brain and that of other mammals
UMICHELLE STARR
10 NOVEMBER 2021
When it comes to the world of mammals, humans tend to be less conspicuous.
Although many animals share certain aspects of our intelligence, they do not reach the same level we do. But to pinpoint why we have developed so much mentally at the emotional level has been subtle; to date, studies have not found much difference between the brains of mammals. Now, we finally have a lead.
A team of researchers from the Massachusetts Institute of Technology (MIT) found that, compared with other mammals, the human brain has a much smaller number of neuronal channels that allow the flow of ions such as calcium, potassium, and sodium.
This flow produces electrical impulses that allow neurons to communicate; having too few of them could mean that the human brain could function effectively, diverting resources from complex brain functions.
"Previous comparative studies have shown that the human brain is made up of just some mammals' brains, so we were surprised to find compelling evidence that human neurons are unique," said MIT neuroscientist Lou Beaulieu-Laroche.
Adopted seeds were planted in 2018, when Beaulieu-Laroche and his colleague Mark Harnet of MIT conducted a study comparing the rat brain with the human brain.
Other findings affect dendrites, branching structures in nerve cells where electrical energy in the brain is obtained by ion channels. From here, the dendrite produces what we call the action force, which transmits the signal forward.
When comparing the brains of these two species, the researchers found that human dendrites had significantly lower levels of these ion channels compared to rat dendrites. This should have been thoroughly investigated.
New research has expanded to include 10 species: shrew, mouse, gerbil, mouse, ferret, guinea pig, rabbit, marmoset, macaque and, yes, human, using extruded tissue samples. in epilepsy patients during brain surgery.
Physical analysis of this brain reveals that ion channel density increases with the size of the neuron, with the exception of one significant factor: the human brain.
This, the researchers concluded, was to maintain ion channel density throughout the brain-size range; therefore, although the shrew had a higher number of neurons than the rabbit or macaque in a given capacity of the brain, the density of ion channels in that volume did not change.
"This construction program is compatible with all nine species of mammals," Harnett said. "What the cortex seems to be trying to do is keep the number of ion channels per unit the same for all species. This means that for a certain cortex, the energy costs are the same, at least for ion channels."
The density of the lowest ion channel in the human brain was shiny, compared to all other brains.
All comparative animals were much smaller than humans, of course, so it may be necessary to examine samples of even larger animals. However, macaque is often used in research as an example of the human brain.
Researchers suspect that evolutionary trade is possible for humans - it is when the biological system loses or undermines the ability to perform well elsewhere.
For example, it takes energy to pump ions through dendrites. By reducing the ion channel density, the human brain may be able to use energy savings elsewhere - either in complex synaptic connections, or the power of rapid action.
"If the brain can save energy by reducing the density of ion channels, it can deplete that energy in other neuronal or circuit processes," Harnett explains.
"We think that people just came out of this building process that had limited cortex size, and found a way to be more energetic, so you use ATP [energy molecules] in volume compared to other animal species."
These findings point out, researchers say, an exciting approach to further research. In future research, the team hopes to explore the pressures of evolution that may have led to these differences, and to identify where, indeed, that extra mental power is going.
The study was published in Nature.
UMICHELLE STARR
10 NOVEMBER 2021
When it comes to the world of mammals, humans tend to be less conspicuous.
Although many animals share certain aspects of our intelligence, they do not reach the same level we do. But to pinpoint why we have developed so much mentally at the emotional level has been subtle; to date, studies have not found much difference between the brains of mammals. Now, we finally have a lead.
A team of researchers from the Massachusetts Institute of Technology (MIT) found that, compared with other mammals, the human brain has a much smaller number of neuronal channels that allow the flow of ions such as calcium, potassium, and sodium.
This flow produces electrical impulses that allow neurons to communicate; having too few of them could mean that the human brain could function effectively, diverting resources from complex brain functions.
"Previous comparative studies have shown that the human brain is made up of just some mammals' brains, so we were surprised to find compelling evidence that human neurons are unique," said MIT neuroscientist Lou Beaulieu-Laroche.
Adopted seeds were planted in 2018, when Beaulieu-Laroche and his colleague Mark Harnet of MIT conducted a study comparing the rat brain with the human brain.
Other findings affect dendrites, branching structures in nerve cells where electrical energy in the brain is obtained by ion channels. From here, the dendrite produces what we call the action force, which transmits the signal forward.
When comparing the brains of these two species, the researchers found that human dendrites had significantly lower levels of these ion channels compared to rat dendrites. This should have been thoroughly investigated.
New research has expanded to include 10 species: shrew, mouse, gerbil, mouse, ferret, guinea pig, rabbit, marmoset, macaque and, yes, human, using extruded tissue samples. in epilepsy patients during brain surgery.
Physical analysis of this brain reveals that ion channel density increases with the size of the neuron, with the exception of one significant factor: the human brain.
This, the researchers concluded, was to maintain ion channel density throughout the brain-size range; therefore, although the shrew had a higher number of neurons than the rabbit or macaque in a given capacity of the brain, the density of ion channels in that volume did not change.
"This construction program is compatible with all nine species of mammals," Harnett said. "What the cortex seems to be trying to do is keep the number of ion channels per unit the same for all species. This means that for a certain cortex, the energy costs are the same, at least for ion channels."
The density of the lowest ion channel in the human brain was shiny, compared to all other brains.
All comparative animals were much smaller than humans, of course, so it may be necessary to examine samples of even larger animals. However, macaque is often used in research as an example of the human brain.
Researchers suspect that evolutionary trade is possible for humans - it is when the biological system loses or undermines the ability to perform well elsewhere.
For example, it takes energy to pump ions through dendrites. By reducing the ion channel density, the human brain may be able to use energy savings elsewhere - either in complex synaptic connections, or the power of rapid action.
"If the brain can save energy by reducing the density of ion channels, it can deplete that energy in other neuronal or circuit processes," Harnett explains.
"We think that people just came out of this building process that had limited cortex size, and found a way to be more energetic, so you use ATP [energy molecules] in volume compared to other animal species."
These findings point out, researchers say, an exciting approach to further research. In future research, the team hopes to explore the pressures of evolution that may have led to these differences, and to identify where, indeed, that extra mental power is going.
The study was published in Nature.
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