We explore the basis of brain diseases on this week's Naked Scientists. We find out what happens to the brain in Huntington's disease, discover the genes behind Alzheimers and a potential treatment for autoimmune diseases like Multiple Sclerosis or MS. Also, the nerve cells in the ear that make loud sounds painful, the extraordinary eyes of the Mantis Shrimp and the world's largest web spinning spider. Plus, how spiders make glue from silk and snot, and in Kitchen Science, we show you a way to fool your brain into making your body do something unexpected.