The anterior insular cortex is a small region of the brain, but it plays a big role in human self-awareness and in neuropsychiatric disorders. A unique cell type, the von Economo neuron (VEN), is located there.  For a long time, the VEN was assumed to be unique to humans, great apes, whales and elephants.

But scientists have recently discovered these brain cells in monkeys. Bring on the self-awareness and empathy?  Not just yet.

Henry Evrard, neuroanatomist at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, found that the VEN occurs also in the insula of macaque monkeys. The morphology, size and distribution of the monkey VEN suggest that it is at least a primal anatomical homolog of the human VEN. 

The insular cortex is a hidden cortical region tucked away deep in the brain – an island within the cortex. Within the last decade, the insula has emerged from darkness as playing a key role in diverse functions linked to our emotions, self-awareness and to social interactions. The very anterior part of the insula in particular is where humans consciously sense subjective emotions, such as love, hate, resentment, self-confidence or embarrassment.

In relation to these feelings, the anterior insula is involved in various psychopathologies. Damage of the insula leads to apathy, and to the inability to tell what feelings we or our conversational partner experience. These inabilities and alteration of the insula are also encountered in autism and other highly detrimental neuropsychiatric disorders including the behavioural variant of frontotemporal dementia (bvFTD).

The von Economo neuron (VEN) occurs almost exclusively in the anterior insula and anterior cingulate cortex. In contrast to the typical neighboring pyramidal neuron that is present in all mammals and all brain regions, the VEN has a peculiar spindle shape and is about three times as large. Evrard and his team at the Max Planck Institute for Biological Cybernetics in Tübingen have discovered VENs in the anterior insula in macaque monkeys, compelling evidence that monkeys may possess at least a primitive form of the human VEN,although they do not have the ability to recognize themselves in a mirror, a behavioral hallmark of self-awareness.

“This means, other than previously believed, that highly concentrated VEN populations are not an exclusivity of hominids, but also occurs in other primate species”, explains Evrard. “The VEN phylogeny needs to be reexamined. Most importantly, the very much-needed analysis of the connections and physiology of these specific neurons is now possible.”

Knowing the functions of the VEN and its connections to other regions of the brain in monkeys could give us clues on the evolution of the anatomical substrate of self-awareness in humans and or even help in better understanding serious neuropsychiatric disabilities or even addictions such as drugs or smoking.

Citation: Henry C. Evrard, Thomas Forro, Nikos K. Logothetis, 'Von Economo Neurons in the Anterior Insula of the Macaque Monkey', Neuron 74(3). doi: 10.1016