Bird neurons use three times less glucose than mammalian neurons

Summary: Neurons in bird brains are more energy efficient than mammalian brains.

source: press cell

Birds have remarkable cognitive abilities and show a high level of intelligence. Compared to mammals of about the same size, bird brains also contain many neurons.

Now a new study reported in current biology September 8 helps explain how birds can preserve more brain cells: Their neurons get less fuel in the form of glucose.

“What surprised us most was not, per se, that neurons consumed less glucose – this could have been predicted by differences in the size of their neurons,” says Kaya von Eugen at Ruhr University Bochum, Germany.

But the magnitude of the difference is so great that the difference in size cannot be the only contributing factor. This means that there must be something additionally different in the birds’ brain that allows them to keep costs very low.”

Researchers explained that a landmark study in 2016 showed that the bird brain contains more neurons than the brain of a similarly sized mammal. Since brains are generally made up of very expensive tissue, it raises an important question: How can birds support so many neurons?

To answer this question, von Eugen and colleagues set out to determine the neural energy budget of birds based on studies of pigeons. They used imaging methods that allowed them to estimate glucose metabolism in birds. They also used modeling methods to calculate the brain’s metabolic rate and glucose consumption.

Their studies found that the pigeon’s brain consumes a surprisingly low amount of glucose (27.29 ± 1.57 μl glucose per 100 g per minute) when the animal is awake. This translates to a surprisingly low budget for brain energy, especially when compared to mammals.

This means that neurons in the bird brain consume three times less glucose than those in the mammalian brain, on average. In other words, their neurons, for reasons that are not yet clear, are less expensive.

Von Eugen says the differences are likely related to the birds’ high body temperature or the specific layout of their brains. The bird’s brain is also smaller on average than the mammalian brain. But their brains retain amazing abilities, perhaps in part because of their less expensive but more numerous neurons.

This indicates a pigeon
Their studies found that the pigeon’s brain consumes a surprisingly low amount of glucose (27.29 ± 1.57 μl glucose per 100 g per minute) when the animal is awake. The image is in the public domain

“Our finding explains how birds are able to support such large numbers of neurons without compromising processing power,” says von Eugen.

“In the long parallel evolution of birds and mammals, birds developed smaller brains with large numbers of neurons capable of advanced cognitive performance.

“And it appears that the combined effect of the distinctive elements of birds—the small size of neurons, the higher body temperature, the particular design of the birds’ brain—may have generated a potential advantage in more efficient neural processing of information: inexpensive neurons with processing power.”

The researchers say they now want to understand more about how bird neurons consume less glucose. While they have ideas about how it works, more study and testing is needed to reveal “the precise mechanistic explanation of how birds get such a high efficiency in neural processing.”

Financing: This work was supported by the Deutsche Forschungsgemeinschaft.

About this Neuroscience Research News

author: Christopher Pinky
source: press cell
Contact: Christopher Pinky – Cell Journalism
picture: The image is in the public domain

original search: open access.
Bird neurons consume three times less glucose than mammalian neuronsWritten by Kaia von Eugen et al. current biology


Summary

see also

This shows the hippocampus and neurons

Bird neurons consume three times less glucose than mammalian neurons

Highlights

  • Awake pigeon brain tissue consumes 27.29 ± 1.57 μl glucose per 100 g per minute
  • This equals 1.86 x 10−9 ±0.2 x 10−9 μmol glucose per neuron per minute
  • Thus, the neural energy budget of pigeons is about 3 x lower than that of mammals
  • This may indicate more efficient neural processing in the avian clade

Summary

Brains are among the most energy-expensive tissues in the mammalian body.

This is mostly caused by expensive neurons with high glucose requirements.

Across mammals, the neural energy budget appears to be constant, which may impose evolutionary constraints on brain development.

Compared to mammals of similar size, birds have higher numbers of neurons, and this feature conceivably contributes to their cognitive prowess.

We set out to determine the neural energy budget of birds to demonstrate how they can metabolically support such large numbers of neurons. We estimated glucose metabolism using positron emission tomography (PET) and 2-[18F]fluoro-2-deoxyglucose ([18F]FDG) as a radioactive in the awake and anesthetized bathroom. Combined with kinetic modeling, this is the gold standard for determining cerebral glucose consumption metabolic rate (CMR .).GLC).

We found that pigeon neural tissue consumed 27.29 ± 1.57 μM glucose per 100 g per minute in the waking state, which translates to a surprisingly low neural energy budget of 1.86 × 10−9 ±0.2 x 10−9 μmol glucose per neuron per minute. This is nearly 3 times lower than the average in mammalian neurons.

The significantly lower neural energy budget explains how pigeons, and possibly other bird species, can support such large numbers of neurons without the associated metabolic costs or compromising neural signals. The advantage of more efficient neural processing of information may have emerged during the distinct development of the bird brain.

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