Elephants use a large number of neurons to control their trunk and ears

(Wikimedia Commons / Byrdyak https://bit.ly/3gQyfuL)

A team of researchers from Humboldt University of Berlin have found that the nucleus of the facial nerve of elephants contains an exceptionally large number of neurons.

The zoologists and neuroscientists, led by Lena Kaufmann attribute this to the control of the trunk and ears.

Modern methods of research allow us to better understand how humans and animals work.

Last year, scientists from 13 laboratories managed to compile an atlas of neurons in the primary motor cortex of mammals based on data from humans, marmosets and mice.

However, despite the large number of studies about the structure and functions of the brain of various animals, much is still unknown.

One of these mysteries is the elephants brain, due to the difficulty of obtaining samples for research.

---

---

THE STUDY
Now, Kaufmann and her team have accumulated enough material to finally study the brains of the Savannah (Loxodonta africana) and Asian elephant (Elephas maximus).

They focused on the neurons in the nucleus of the facial nerve, which control the muscles of the face of four individuals of each species.

To count neurons in the nucleus of the facial nerve of elephants, the authors used two methods:

• the method of optical fractionation
• the method of counting all neurons in every tenth slice

Both methods showed similar results:

• an average of 62961-63202 neurons in the bush elephant
• 52146-54103 in the Asian elephant

Next, Kaufmann’s team tested whether the large number of facial neurons was really associated with the elephants' large brain weight of 4.7 kilograms alone.

They conducted an allometric analysis, which shows the relationship between two quantities (the number of neurons in the nucleus of the facial nerve) in the form of a power law equation.

This allows scale symmetry to be expressed, which is important when comparing mammals of different sizes.

Using this method, the authors built a logarithmic graph comparing the number of facial neurons in elephants and other mammalian species.

There were several times more such neurons in elephants than expected in primates in the translated scale - the difference was three 95% confidence intervals.

The next step was the comparison of the subnuclei responsible for the movement of facial muscles of the two species of elephants and other mammals.

(Michael Brecht / Science Advances, 2022 https://bit.ly/3SIwi0V)

Kaufmann hypothesized that the dorsal and lateral subnuclei in elephants may be responsible for the dorsal and ventral trunk muscles.

The authors based their belief on several reasons. But they focused on the topography of the nucleus regions responsible for different facial muscles in mammals, amd the large size and elongated shape of the dorsal and lateral subnucleus

Their assumptions were also confirmed by comparing the number of axons in the branches of the facial nerve and the corresponding subnuclei.

---

---

HOWEVER
The question also remained as to why bush elephants have more facial neurons than Asians.

One reason is the size of the ears. It takes about 11965 neurons to control large ears in bush elephants, and 7498 in Asian elephants.

In addition, the trunk of bush elephants has two processes, which allows them to capture objects

The Asian elephants do not have such processes, so they can only take the object by completely hugging him with their trunk.

Sources:

• Science Advances: https://www.science.org/doi/10.1126/sciadv.abq2789
• Phys.org: https://phys.org/news/2022-10-trunk-dexterity-berlin-scientists-decipher.html
• IDW-Online: https://idw-online.de/de/news803641

---

---

If you like my content, please consider following, upvoting and commenting. I really appreciate it.
Follow my Telegram channel: https://t.me/stemsteemit

---

---

#science #animals #elephants #brain #neuroscience #news #nftmc