Evolution of the elephant brain: A paradox between brain size and cognitive behavior

Elephants have the greatest volume of cerebral cortex of any terrestrial mammal, exceeding that of humans by threefold. Paradoxically perhaps, their performance in tests of primate-like, time-sensitive, or intricate cognitive tasks is unimpressive compared with even chimpanzees. This paradox may be explained on the basis that, rather than evolving toward increasing localization of neuronal projections in the cerebral cortex to maintain interconnectivity and speed of information processing, as seen in large-brained primates, the elephant brain evolved with a bias toward more global, transcortical projections, with reduced local circuit interactions and greatly prolonged information-processing time. On the other hand, this cytoarchitectural model for the elephant brain would appear to provide the neurological basis for the extraordinary long-term and extensive spatial-temporal and social memory abilities of elephants.