Dolphins are famous for their remarkable cognitive abilities. So, we would expect them to have a large prefrontal cortex (PFC). But there seems to be none! At least at the expected place in the frontal cortex. How is that possible? Now biopsychologists and clinical scientists from Bochum as well as veterinary scientists from the university of Padua could solve the mystery. Using MRI, they tracked the fibers ascending from the medio-dorsal thalamic nuclei (MD) to the cortex. In land mammals the MD projects to the PFC. To their surprise, they discovered that these fibers ascended to the lateral frontal cortex. So, possibly dolphins have a large PFC, but since their large brain could not grow even more frontally, their PFC was pushed sideways during evolution. The picture shows a dolphin brain along with the brains of a rat, a pigeon and the model of a human brain.

Gerussi, T., Graïc, J-M, Peruffo, A., Behroozi, M., Schlaffke, L., Huggenberger, S., Güntürkün, O., Cozzi, B., The prefrontal cortex of the bottlenose dolphin (Tursiops truncatus Montagu, 1821). A tractography study and comparison with the human, Brain Structure Function, 2023, 228: 1963–1976.