Von Economo neurons (VENs), also called spindle neurons, are a specific class of mammalian cortical neurons characterized by a large spindle-shaped soma (or body) gradually tapering into a single apical axon (the ramification that transmits signals) in one direction, with only a single dendrite (the ramification that receives signals) facing opposite. Other cortical neurons tend to have many dendrites, and the bipolar-shaped morphology of von Economo neurons is unique here. Von Economo neurons are found in two very restricted regions in the brains of hominids (humans and other great apes): the anterior cingulate cortex (ACC) and the fronto-insular cortex (FI) (which each make up the salience network). In 2008, they were also found in the dorsolateral prefrontal cortex of humans. Von Economo neurons are also found in the brains of a number of cetaceans, African and Asian elephants, and to a lesser extent in macaque monkeys and raccoons. The appearance of von Economo neurons in distantly related clades suggests that they represent convergent evolutionspecifically, as an adaptation to accommodate the increasing size of these distantly-related animals' brains. Von Economo neurons were discovered and first described in 1929 by Austrian psychiatrist and neurologist Constantin von Economo (1876–1931). Name Von Economo neurons are named after the Austrian neurologist Constantin von Economo, who first described these neurons in 1926. Function Von Economo neurons are relatively large cells that may allow rapid communication across the relatively large brains of great apes, elephants, and cetaceans. Although rare in comparison to other neurons, von Economo neurons are abundant, and comparatively large, in humans; they are however three times as abundant in cetaceans. Evolutionary significance The discovery of von Economo neurons in diverse whale species has led to the suggestion that they are "a possible obligatory neuronal adaptation in very large brains, permitting fast information processing and transfer along highly specific projections and that evolved in relation to emerging social behaviors." The apparent presence of these specialized neurons only in highly intelligent mammals may be an example of convergent evolution. Their restriction among the primates to great apes leads to the hypothesis that they developed no earlier than 15–20 million years ago, prior to the divergence of orangutans from the African great apes. Recently, primitive forms of von Economo neurons have also been discovered in macaque monkey brains and raccoons. In the anterior cingulate cortex In 1999, American neuroscientist John Allman and colleagues at the California Institute