If you look carefully, it is very similar to the neural system in any bilateral https://www.britannica.com/science/nervous-system/Diffuse-ne... . It is twisted following the deformation of the body inside the shell. Compare it with https://entomology.unl.edu/charts/nervous.shtml
In our central nervous system one of the ganglia grow tooooooo much. Moreover, the olfactory part of it grow tooooooooooooooooooooooooo much.