Cortical Surface Structure Analysis in Sharks Using Magnetic Resonance Imaging (MRI)

Kara E. Yopak¹, Greg T. Balls¹, Lawrence R. Frank¹

The shark cerebellum has morphologically diversified throughout vertebrate evolution. We have previously developed a qualitative visual grading index for cerebellar foliation (n=60). Here we provide a more robust method using MRI in conjunction with rigorous 3D shape analysis methods to quantify our previous scheme. Quantification was based upon the number of parameters necessary to accurately describe the cortical surface decomposed onto a spherical harmonic basis using the spherical harmonics decomposition (SHD). These methods, previously used to characterize global brain shape in humans, were preliminarily applied to a small number of representative shark species. More foliated shark brains required a more complex SHD to accurately fit its cortical surface.