This fronto-insular cortex is closely connected to the insula, a region that is roughly the size of a thumb in each hemisphere of the human brain. The insula and fronto-insular cortex are part of the insular cortex, wherein the elaborate circuitry associated with spatial awareness are found, and where self-awareness and the complexities of emotion are thought to be generated and experienced. Moreover, this region of the right hemisphere is crucial to navigation and perception of three-dimensional rotations. The largest number of ACC von Economo neurons are found in humans, fewer in the gracile great apes, and fewest in the robust great apes. In both humans and bonobos they are often found in clusters of 3 to 6 neurons. They are found in humans, bonobos, chimpanzees, gorillas, orangutans, some cetaceans, and elephants. While total quantities of ACC von Economo neurons were not reported by Allman in his seminal research report (as they were in a later report describing their presence in the frontoinsular cortex, below), his team's initial analysis of the ACC layer V in hominids revealed an average of ~9 von Economo neurons per section for orangutans (rare, 0.6% of section cells), ~22 for gorillas (frequent, 2.3%), ~37 for chimpanzees (abundant, 3.8%), ~68 for bonobos (abundant/clusters, 4.8%), ~89 for humans (abundant/clusters, 5.6%). All of the primates examined had more spindle cells in the fronto-insula of the right hemisphere than in the left. In contrast to the higher number of spindle cells found in the ACC of the gracile bonobos and chimpanzees, the number of fronto-insular spindle cells was far higher in the cortex of robust gorillas (no data for Orangutans was given). An adult human had 82,855 such cells, a gorilla had 16,710, a bonobo had 2,159, and a chimpanzee had a mere 1,808despite the fact that chimpanzees and bonobos are great apes most closely related to humans. Von Economo neurons have been located in the Dorsolateral prefrontal cortex of humans and elephants. In humans they have been observed in higher concentration in Brodmann area 9 (BA9)mostly isolated or in clusters of 2, while in Brodmann area 24 (BA24) they have been found mostly in clusters of 2-4.