An article on the Smithsonian website, Brain Cells for Socializing, discusses Eco cells. (here)

“The von Economo neurons are the most striking finding of recent years in comparative brain research, in which scientists tease out fine differences among species. Neuroanatomist Patrick Hof and his colleagues at the Mount Sinai School of Medicine in Manhattan first stumbled across the neurons in human brain specimens in 1995… Most neurons have cone- or star-shaped bodies with several branching projections, called dendrites, that receive signals from neighboring cells. But von Economo neurons are thin and elongated, with just one dendrite at each end. They are four times bigger than most other brain cells, and even in species that have the cells, they are rare…

The spinal shaped cells occur only in the anterior cingulate cortex and the frontal insula. About 100 mammals have been examined of the unusual cells but they are found only in great apes , elephants, humpback whales, sperm whales, fin whales, orcas and bottle-nosed dolphins. The common thread here is that these animals are (1) very social (2) with large brains. Whales and elephants, like people and great apes, have extremely large brains and a prolonged juvenile stage during which they learn from their elders.

In 1999, the scientists reported that all great ape species had von Economo cells, but lesser primates, such as macaques, lemurs and tarsiers, did not. That meant the neurons evolved in a common ancestor of all the great apes about 13 million years ago, after they diverged from other primates but well before the human and chimp lineages diverged about six million years ago…”

William Seeley, a neurologist at the University of California at San Francisco, studies a poorly understood neurodegenerative disease called frontotemporal dementia. Patients suffer a breakdown in their character, losing social graces and empathy, turning insensitive, erratic and irresponsible. Marriages and careers implode. Many patients seem to lack physical self-awareness: when diagnosed with other illnesses, they deny having any problems. Brain imaging studies of patients with the dementia have uncovered damage to frontal areas of the brain….Analyzing brains from deceased patients, the scientists discovered that, in fact, about 70 percent of von Economo neurons in the ACC had been destroyed, whereas neighboring brain cells were largely unaffected. “It is very clear that the original target of the disease is these cells, and when you destroy these cells you get the whole breakdown of social functioning,” says Allman. “That’s a really astounding result that speaks to the function of the cells about as clearly as anything can.”

It is possible that similar cells with a similar function occur in many social animals but that it is only in large brains where extra speed is required that they take on the distinctive spinal shape and large size.