Nature: Although the function of prions—commonly associated with “mad cow disease”—is still unknown, they can also be beneficial to the developing brain. Prions occur in two main forms: normal or misfolded. The normal version, called cellular prion protein, is present in all tissues throughout the body, including neurons. To learn more about their function, researchers in Italy studied the brains of mice, both healthy animals and ones that had been genetically engineered to lack the prion protein, writes Mo Costandi for Nature. By electrically stimulating cells in hippocampus tissue sliced from both sets of animals, the researchers determined that in healthy mice the neuronal connections were strengthened and in the genetically engineered mice the neuronal connections were weakened. Further research is needed to better understand the function of prions and to see whether they serve key functions in other parts of the brain, such as the visual cortex.