The unique brain of an elephant
August 12, 2018
Conservationists have observed August 12 as World Elephant Day to raise awareness about the conservation of these magnificent animals. Elephants have many fascinating features, from their incredibly magnificent trunks to their memory abilities and complex social lives.
But their brains are rarely discussed, although the reason is that the brain of such a large animal is quite large (about 12 pounds). In fact, until recently, little was actually known about the elephant's brain, in part because it is extremely difficult to obtain well-preserved tissue suitable for microscopic studies.
The door was opened by the first efforts of neurobiologist Paul Menger at the University of the Witwatersrand in South Africa, who in 2009 obtained permission to extract and preserve the brains of three African elephants as part of a larger population management. But had to be killed. Strategies In this way we have learned more about the elephant brain than ever before in the last 10 years.
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The research shared here was conducted in 2009-2011 in collaboration with Paul Menger of Colorado College, Columbia University anthropologist Chat Sherwood and Patrick Hoff, a neuroscientist at the Icon School of Medicine in Mount Sinai. Our goal was to find the shapes and sizes of neurons in the elephant cortex.
My lab group has long been interested in the shape or form of neurons in mammalian cortex. The cortex forms a thin, outer layer of neurons (nerve cells) that cover the two cerebral hemispheres. It is closely related to higher cognitive functions such as integrated voluntary movement, integration of sensory information, sociocultural learning and memory storage that define an individual.
These images illustrate the process of removing a small portion of the cerebral cortex from the right cerebral hemisphere of an elephant. This tissue is stained and placed on a slide of glass so that, under a microscope, one can see individual neurons and trace them in three directions. Photo by Robert Jacobs.
The arrangement and shape of neurons in the cortex is relatively similar in mammals - or so we thought after decades of research into human and non-human primate brains, and the brains of mice and cats. As we found when we were able to analyze the elephant's brain, the shapes of the elephant's cortical neurons are very different from what we have ever seen before.
How neurons are perceived and quantified.
The process of detecting neuronal morphology begins with scarring of brain tissue when it lasts for a certain period of time (chemically preserved). In our laboratory we use a technique more than 125 years old called the Golgi stain, named after the Italian biologist and Nobel laureate Camilo Golgi (1843-1926).
This method laid the foundation for modern neuroscience. For example, the Spanish neurovanatomist and Nobel laureate Santiago Ramon y Cajal (1852-1934) used this technique to provide a roadmap for what neurons look like and how they are connected to each other.
Golgi scars affect only a small percentage of neurons, leaving individual cells relatively isolated with a clear background. It represents dendrites, or branches, that form the acceptable surface area of these neurons. Just as the branches on a tree provide light for photosynthesis, so do dendrites in neurons, allowing cells to receive and synthesize information from other cells. The more complex the dendritic systems, the more information a particular neuron can handle.
Once we spot neurons, we can detect them in three dimensions under a microscope with the help of computers and special software, which reflect the complex geometry of neuronal networks. In this study, we traced 75 neurons in elephants. Each tracing took one to five hours, depending on the complexity of the cell.
What do elephant neurons look like?
Even after years of research, it is still interesting to see the tissue under a microscope for the first time. Each scar is a walk in a different nerve forest. When we examined the tissue parts of the elephant, it was clear that the basic architecture of the elephant cortex was different from any other mammal that has been examined to this day - including its close relatives, the manatee. And rock hierarchies.
Detection of the most common neurons (pyramidal neurons) in the cerebral cortex of many species. Note that elephants have large branches of apical dendrites, while all other species have more single, ascending apical dendrites. Scale bar = 100 micrometers (or 0.004 of an inch). Photo by Bob Jacobs.
There are three major differences between the cortical neurons found in elephants and those found in other mammals.
First, the dominant cortical neuron in mammals is the pyramidal neuron. These elephants are also prominent in the cortex, but their structure is very different. Instead of having a single dendrite that comes from the top of the cell (called apical dendrite), the apical dendrites in elephants usually form large branches as they ascend to the surface of the brain. Instead of a single, long branch like a pine tree, the elephant apical dendrite resembles two human arms reaching upwards.
A type of cortical neuron in elephants that is rare if ever observed in the cortex of other mammals. Note that all of these are characteristic of dendrites that spread from the back of the cell body, sometimes at great distances. Scale bar = 100 micrometers (or 0.004 of an inch). Photo by Bob Jacobs.
Second, elephants exhibit a much wider range of cortical neurons than other species. Some of these, such as flat pyramidal neurons, are not found in other mammals. One of the characteristics of these neurons is that their dendrites travel long distances from the cell body. In other words, like the apical dendrites of the pyramid cells, these dendrites also spread like human arms up to the sky.
Third, the total length of pyramidal neuron dendrites in elephants is equal to that of humans. However, they are configured differently. The neurons of the human pyramid have a large number of short branches, while the elephant has a very small number of very long branches. While the neurons in the primitive pyramid appear to be designed to sample very accurate inputs, the dendritic configuration in elephants suggests that their dendrites sample a very wide range of inputs from a variety of sources.
Taken together, these morphological features suggest that neurons in the elephant cortex can synthesize a wider range of inputs than cortical neurons in other mammals.
Cognitively, my colleagues and I believe that the integrative cortical circuit in elephants supports the idea that they are primarily meditative animals. Primate brains, by contrast, are known for their quick decision-making and quick response to environmental stimuli.
A toothless elephant shows compassion for a young orphaned elephant trying to find its way into a Kenyan bush.
Researchers like Dr. Joyce Poole's observations on the natural habitat of elephants show that elephants are indeed thinking, understanding, curious and thinking creatures. Their large brains, with such a diverse collection of interconnected, complex neurons, appear to provide the neural basis for the elephant's state-of-the-art cognitive abilities, including social communication, tool building and use, and creative issues. Solutions, empathy and self-knowledge, including ideology. Of the brain
The brains of all species are unique. In fact, even the brains of certain species are unique. However, the special shape of the elephant's cortical neurons reminds us that there are definitely more than one way to wire the intelligent brain.
Bottom line: The cells that transmit nerve impulses to this part of the elephant's brain, which are responsible for functions such as learning and memory, are different in structure from other mammals.
