Von Economo neuron
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Spindle or Von Economo neurons (VENs) occur in primates (humans, gorillas, chimpanzees, bonobos, and orangutans), and while previously thought to be unique to the great apes, have more recently been found in cetaceans (humpback, fin, killer, and sperm whales).
Neuronal Type: Projection Neuron
VENs are bipolar neurons with one large apical axon and a single basal dendrite. They are found exclusively in layer Vb of the anterior cingulate cortex (ACC) and frontoinsular cortex (FI), and have also recently been identified in human dorsolateral prefrontal cortex (DLPFC) (Brodmann area 9).  Its large apical axon and high-volume, elongated soma is similar to that of the fast-conducting, cortical pyramidal neuron, but the VEN lacks the pyramidal neuron's large array of basal dendrites and the average VEN is 4.6 times larger than the average layer 5 pyramidal cell.  VENs are relatively rare, and thought to make up 1-2% of the Layer 5 neurons in ACC.  In FI, VENs are 30% more numerous in the right hemisphere than the left. 
- Neurotransmitter Receptors: vasopressin 1a, dopamine d3, serotonin 2b 
Though currently unknown where VENs ultimately project to, studies in monkeys indicate that ACC and FI connect to a wide range of areas: prefrontal, orbitofrontal, insular and anterior temporal cortices, amygdala, hypothalamus, and various thalamic nuclei.
Ontogeny and Phylogeny
VENs develop late both ontogenetically and phylogenetically.
They first appear in the 35th week of gestation; at birth only about 15% of the postnatal number are present. The adult number is attained by 4 years of age. 
Analyses of over 30 mammalian species have failed to find VENs except in primates and cetaceans. Among primates, including the lesser apes (gibbons), VENs have only been observed in the great apes (humans, gorillas, chimpanzees, bonobos, and orangutans).
Among hominids, humans have the most VENs, both in terms of absolute number and relative percentage compared to total number of neurons. In decreasing order of total number of VENs, they are found in humans, bonobos, chimpanzees, gorillas, and orangutans. In humans and bonobos, VENs are distributed in clusters of 3-6 neurons, while in other apes they show no such pattern of distribution. [3,4]
 Von Economo, C. and Koskinas, G. (1925) Die Cytoarchitectonik der Hirnrinde des erwachsenen Menschen, Springer
 Nimchinsky, E.A. et al. (1995) Spindle neurons of the human anterior cingulate cortex. J. Comp. Neurol. 355, 27–37
 Nimchinsky, E.A. et al. (1999) A neuronal morphologic type unique to humans and great apes. Proc. Natl. Acad. Sci. U. S. A. 96, 5268–5273
 Allman, J. et al. (2002) Two phylogenetic specializations in the human brain. Neuroscientist 8, 335–345
 Sherwood, C.C. et al. (2003) Evolution of specialized pyramidal neurons in primate visual and motor cortex. Brain Behav. Evol. 61, 28–44
 Allman, J.M. et al. (2005) Intuition and autism: a possible role for Von Economo neurons. TRENDS in Cognitive Sciences 9:8, 367-373
 Fajardo, C. et al. (2008) Von Economo neurons are present in the dorsolateral (dysgranular) prefrontal cortex of humans. Neuroscience Letters 435:3, 215-218