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

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

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

In this article we explain what these types of neurons consist of, where we can locate them, what is their structure and what functions they perform, and what happens when these cells develop anomalous.

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Von Economo neurons: definition, location and development

Von Economo neurons, also known as spindle neurons, are named after the Austrian psychiatrist and neurologist Constantine F. Von Economo, who 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 neurons. specialized cells located in layer Vb of the anterior cingulate cortex and frontal insular cortex mostly.

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

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

According to research, spindle cells appear to have evolved about 15 million years ago, before the evolutionary divergence of orangutans and hominins. The discovery of it in some whales suggests that there could 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 function.

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

Structure

Von Economo described this type of cell as neurons showing a spindle shape and unusual length., oriented perpendicular to the pial surface of the cortex, with a large apical axon and a single basal dendrite, almost the same width as its soma.

Its large apical axon and elongated soma with a large volume are similar to those of the cortical pyramidal neuron, but von Economo neurons they lack the numerous basal dendrites that pyramidal cells do have, and instead receive inputs from a relatively small subset of the cortex. little; 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 may perform similar functions, and because the rate at which they neurons conduct information usually covary with the diameter of their axons, large von Economo neurons can do so very quickly, compared with other neurons.

Still, von Economo neurons are relatively rare in a region like the anterior cingulate cortex, since they comprise only 1-2% of the total number of neurons in this brain area.

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

functions

The investigations carried out suggest 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, empathy, emotions, and monitoring of visceral autonomic activity, Among other functions.

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

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 shown to be received in the Brodmann area 10, in the frontopolar cortex, where it is thought that the regulation of the cognitive dissonance and disambiguation between alternatives.

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

The anterior cingulate cortex is also involved in autonomic functions, including motor and digestive functions., while also playing a role in regulating blood pressure and heart rate.

The significant olfactory and taste abilities 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 should also be noted that the decreased 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 neural integration reduced

Disorders related to the abnormal development of these neurons

Abnormal development of von Economo neurons has been linked to various personality disorders and neurodevelopmental disorders., especially those characterized by distortions of reality, thought disorders, language disorders and social withdrawal.

In addition, abnormal development and functioning of this type of neuron has been implicated in disorders such as autism, since in various studies it has been possible to verify 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 insights are combined with slower deliberative judgments.

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

Besides, selective degeneration of spindle neurons has also been observed in diseases such as Alzheimer's 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 seen that 70% of Von Economo neurons were damaged.

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

Bibliographic references:

• Allman, J. M., Watson, K. K., Tetreault, N. A., & Hakeem, A. AND. (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.