These types of neurons are 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, 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 that have to do with socialization, empathy, intuition or complex decision-making.
In this article we explain what these types of neurons consist of, where we can locate them, what their structure is and what functions they perform, and what happens when these cells develop abnormally.
We recommend you read: [“Types of neurons: characteristics and functions”] (Types of neurons: characteristics and functions)
Von Economo neurons: definition, location and development
Von Economo neurons, also known as spindle neurons, are named after the Austrian psychiatrist and neurologist Constantin F. Von Economo, who in 1926 provided a detailed description of the morphology and cortical distribution of these neurons.
Von Economo was also the first scientist to show that these spindle-shaped cells are specialized neurons that are located in the Vb layer of the anterior cingulate cortex and the frontal insular cortex, mainly.
Spindle neurons, unlike most types of nerve cells, are present in great apes (gorillas, chimpanzees, bonobos, and orangutans) and in humans, but are absent in other 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 postnatal numbers are present, and by four years, adult numbers are present.
According to research, spindle cells appear to have evolved approximately 15 million years ago, before the evolutionary divergence of orangutans and hominids. Its discovery 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 functions.
The fact that these neurons have been discovered in other species (such as whales) suggests that they could be a mandatory neural adaptation in large brains, allowing rapid processing and transfer of information along highly specific projections, and that evolved in relation to emerging social behaviors.
Von Economo described this type of cells 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, with a width practically equal to that of its soma.
Their large apical axon and large elongated soma are similar to those of the cortical pyramidal neuron, but Von Economo neurons lack the numerous basal dendrites that pyramidal cells do, and instead receive inputs from a relatively small subset of cortex; in addition, spindle neurons are approximately five times larger than pyramidal neurons in layer V (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 co-varies with the diameter of their axons, large Von Economo neurons can do so very quickly, in comparison with other neurons.
However, Von Economo neurons are relatively rare in a region such as the anterior cingulate cortex, comprising only 1-2% of all 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.
Research suggests that the frontal insular cortex and the anterior cingulate cortex, the brain regions in which a greater number of spindle neurons have been located, are involved in social reasoning, empathy, emotions, and activity monitoring autonomic visceral, among other functions.
The anterior cingulate cortex has projections towards the frontopolar cortex, which has been associated with processes of cognitive dissonance and uncertainty. Given the morphology of Von Economo cells, 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. quick decision making and in the resolution of cognitive dissonance processes.
Spindle neurons help channel neural signals from regions deep in 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 regulation of cognitive dissonance and disambiguation between alternatives are thought to occur .
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 in error detection.
The anterior cingulate cortex is also involved in autonomic functions, including digestive and motor functions, while also playing a role in the regulation of 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
The abnormal development of Von Economo neurons has been linked to various personality disorders and neurodevelopmental disorders, especially those characterized by distortions of reality, thought disturbances, language disorders, and social withdrawal.
Furthermore, the development and abnormal functioning of this type of neuron has been implicated in disorders such as autism, since various 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.
Von Economo neurons have been proposed to be 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 rapid 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 intuitional processes.
On the other hand, a 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, 70% of Von Economo neurons have been found to be 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.
Allman, JM, Watson, KK, Tetreault, NA, & Hakeem, AY (2005). Intuition and autism: a possible role for Von Economo neurons. Trends in cognitive sciences, 9 (8), 367-373 ..
Seeley, WW, Carlin, DA, Allman, JM, Macedo, MN, Bush, C., Miller, BL, & DeArmond, SJ (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, KK, Jones, TK, & Allman, JM (2006). Dendritic architecture of the von Economo neurons. Neuroscience, 141 (3), 1107-1112.