Von Economo neurons: what they are, where they are located, and their functions.

This type of neuron is associated with complex cognitive processes, such as socialization.

Von Economo neurons are a special class of nerve cells, first described just under a century ago.first described a little less than a century ago, characteristic of humans and great apes.

They are special because of their particular spindle-shaped structure and because they are involved in complex cognitive processes related to socialization, empathy, intuition or complex decision-making.

In this article we explain what these neurons are, where they are located, their structure and functions, and what happens when these cells develop abnormally.

• We recommend reading: ["Types of neurons: characteristics and functions"](Types of neurons: characteristics and functions).

Von Economo neurons: definition, localization and development.

Constantin Von Economo, the discoverer of spindle neurons.

Von Economo neurons, also known as spindle neurons, are named after the Austrian psychiatrist and neurologist Constantin F. Von Economowho in 1926 provided a detailed description of the morphology and cortical distribution of this type of neuron.

Von Economo was also the first scientist to show that these spindle cells are specialized neurons located mainly in layer Vb of the anterior cingulate cortex and frontal insular cortex.

Spindle neurons, unlike most types of nerve cells, are present in the great apes (gorillas, chimpanzees, chimpanzees). (gorillas, chimpanzees, bonobos and orangutans) and in humans, but absent in other primates.

Von Economo neurons develop late, both ontogenetically and phylogenetically. These cells first appear in the 35th week of gestation; at birth, only about 15% of postnatal numbers are present, and by four years of age, adult numbers are present.

According to research, spindle cells apparently evolved about 15 million years ago, before the evolutionary divergence of orangutans and hominids. Their discovery in some whales suggests that there may be a second, independent evolution of this type of neuron.

The observation that Von Economo cells occur in a highly significant group of animals has led to speculation that they are of great importance in human evolution and brain functions.

The fact that these neurons have been discovered in other species (such as whales) suggests that they may be an obligatory neural adaptation in large brains, allowing rapid processing and transfer of information along highly specific projections, and that they evolved in relation to emergent social behaviors.

Structure

Von Economo described this cell type as neurons showing a spindle shape and an unusual lengthoriented perpendicularly to the pial surface of the cortex, with a large apical axon and a single basal dendrite, with a width practically equal to that of its soma.

Their large apical axon and elongated soma with a large volume are similar to those of the cortical pyramidal neuron, but Von Economo neurons lack the numerous basal dendrites that pyramidal cells have, and instead receive inputs from a relatively small subset of the cortex; in addition, spindle neurons are approximately five times larger than layer V pyramidal neurons (on average).

Their structural similarity to pyramidal neurons suggests that these neurons can perform similar functions, and because the speed at which neurons conduct information often covaries with the diameter of their axons, large Von Economo neurons can do so very rapidly compared with other neurons.

However, Von Economo neurons are relatively rare in a region such as the anterior cingulate cortex, comprising only 1-2% of the total number of neurons in this brain area.

In the frontal insular cortex, these neurons are 30% more numerous in the right hemisphere than in the left hemisphere.A process of hemispheric differentiation occurs in the first four years of postnatal development in humans.

Functions

Research suggests that the frontal insular cortex and the anterior cingulate cortex, the brain regions in which the greatest number of spindle neurons have been located, are involved in social reasoning, are involved in social reasoning, empathy, emotion and monitoring of visceral autonomic activity, among other functions.among other functions.

The anterior cingulate cortex has projections to the frontopolar cortex, which has been linked to processes of cognitive dissonance and uncertainty. Given the morphology that Von Economo cells possess, they have been described as fast projection neurons, and due to the functions of the areas from which they are believed to receive and project information, it is believed that they would play an important role in intuition, rapid decision making and in the resolution of cognitive dissonance processes.

Spindle neurons help channel neural signals from deep regions of the cortex to relatively distant parts of the brain. Signals from the anterior cingulate cortex have been observed to be received in Brodmann's area 10 in the frontopolar cortex, where the regulation of cognitive dissonance and disambiguation between alternatives is thought to occur.

On the other hand, in humans, intense emotions activate the anterior cingulate cortex as it transmits neural signals from the amygdala, a primary emotion processing center, to the frontal cortex. The anterior cingulate cortex is also active during demanding tasks requiring judgment and discrimination, as well as in error detection.

The anterior cingulate cortex is also involved in autonomic functions, including motor and digestive functions, as well as playing an important role in the development of the anterior cingulate cortex.The anterior cingulate cortex is also involved in autonomic functions, including motor and digestive functions, and plays a role in the regulation of Blood Pressure and heart rate.

Significant olfactory and gustatory capacities of the cingulate cortex and frontal insular cortex appear to have dissipated during evolution, to now perform enhanced functions related to higher cognition, ranging from planning and self-awareness to role-playing and deception.

It is also noteworthy that the impaired olfactory function of humans, compared to other primates, could be related to the fact that spindle cells located in crucial neural centers have only two dendrites instead of many, resulting in reduced neural integration.

Disorders related to the abnormal development of these neurons.

Abnormal development of Von Economo neurons has been linked to a number of personality disorders and neurodevelopmental disorders, especially those characterized by distortion of the personality.especially those characterized by distortions of reality, thought disturbances, language disorders and social withdrawal.

In addition, the abnormal development and functioning of this type of neurons has been implicated in disorders such as autism, since several studies have shown that spindle neurons participate in the cognitive processes involved in the rapid intuitive evaluation of complex situations. In this sense, it has been suggested that they could be part of the circuits that support human social networks.

It has been proposed that Von Economo neurons are related to brain areas associated with theory of mind, through the transmission of information from the cingulate cortex and frontoinsular areas to the frontal and temporal cortex, where fast intuitions are combined with slower deliberative judgments.

In autism spectrum disorders, spindle neurons would not develop properly, and this failure could be partially responsible for the social difficulties that emerge from applying faulty intuition processes.

On the other hand, selective degeneration of spindle neurons has also been observed in diseases such as Alzheimer's disease and dementia.. For example, in patients with frontotemporal dementia, a neurodegenerative disorder that causes the person to lose empathy and become erratic and insensitive, it has been found that 70% of Von Economo neurons were damaged.

In closing, it should be noted that some research has suggested that abnormal development of these neurons may be related to the pathogenesis of schizophrenia, although no conclusive results have been obtained to date.

Bibliographical references:

• Allman, J. M., Watson, K. K., Tetreault, N. A., & Hakeem, A. Y. (2005). Intuition and autism: a possible role for Von Economo neurons. Trends in cognitive sciences, 9(8), 367-373..

• Seeley, W. W., Carlin, D. A., Allman, J. M., Macedo, M. N., Bush, C., Miller, B. L., & DeArmond, S. J. (2006). Early frontotemporal dementia targets neurons unique to apes and humans. Annals of Neurology: Official Journal of the American Neurological Association and the Child Neurology Society, 60(6), 660-667.

• Watson, K. K., Jones, T. K., & Allman, J. M. (2006). Dendritic architecture of the von Economo neurons. Neuroscience, 141(3), 1107-1112.