Neurobiology of the Von Economo Neurons and related circuits

Von Economo Neurons (VENs) were first described in 1925, and "rediscovered" during neuroanatomical studies conducted in the late 1990's. VENs are of particular interest to neuroanatomists because the available data indicated that these cells were found only in the brains of humans and great apes and occurred more abundantly in the human than in the great ape brain. VENs also show a protracted developmental time course and do not achieve adult numbers in humans until age 4 years. The renewed interest in the specialized characteristics of VENs was fueled in part by speculation that these cells are integral to the evolution and development of complex cognitive functions, possibly related to social interactions. Support for such speculation was bolstered by the autopsy evidence suggesting that VEN abnormalities occur in individuals with diseases such as Autism and dementia. Although it is still far from certain how these unusual, spindle-shaped neurons contribute to behavior, their unusual morphology and integration into neural circuits known to influence complex cognitive functions, warrant careful study.

Neuroanatomical studies are painstaking and usually carried out by independent investigators aiming to answer a narrow rather than broad question. The strength of the collaboration is its ability to make a dedicated and comprehensive effort, using modern histochemical, anatomical, and genetic methods, to characterize the Von Economo Neurons across a range of species and at different times during.

The collaborative has already reported startling findings. An anatomical examination of several species of large-brained mammals, undertaken in response to some questions posed during the proposal review, resulted in data challenging the idea that VENs are found uniquely in the brains of Great Apes, particularly humans. While it remains true that VENs are much more prevalent in the brains of humans than in other species, VENs have now been identified in the brains of several types of whales and in elephants. The evidence suggests that VENs have independently evolved at least three times. Further analysis could identify additional occurrences. One important question is why this has happened. The answer is tied to further characterizing their function.

In phase two, the collaborators propose to continue using a multi-pronged neuroanatomical, genetic, and electrophysiological approach to characterize VENs in humans and non-human species. One hypothesis is that the large bi-polar structure of VENs allows big-brained mammals the circuitry needed to integrate input from several cortical areas during rapid decision-making. In humans, VENs may participate in the quick decisions we call "intuitions", particularly important in complex social situations.