Fig 1. PET scans show that gray matter of the dolphin cerebrum and cerebellum have the highest metabolism in the brain.

Frontal (A, B) and horizontal (C, D) views of a Tursiops truncatus brain after FDG PET (A, C) and MRI (B, D) scans. Images have been modified from previous publications with the authors’ permission [7,8]. The color map indicates the relative degree of glucose metabolism. The images demonstrate that high metabolic areas (i.e., areas of increased glucose consumption; red) are mainly concentrated in the gray matter of the cerebral cortex and cerebellum, with the exception of smaller sub-cortical nuclei (e.g., inferior colliculi; thalamic gray matter). The PET and MRI scans are from the same healthy dolphin that was trained to lie still in the scanner.