What causes bright spots in 1 year old brain mri?

Lots of things. "bright spots" on an MRI have various causes. They can range from benign, insignificant findings to infections, injuries, metabolic problems and more. An MRI is only a tool, and the findings need to be put in the context of the patient's clinical condition. Mri's are often ordered unnecessarily and then odd findings (like bright spots) can make a straightforward case much more confusing.
Variety of factors. There can be a large variation in the appearance of the brain at this early age. Spots could represent areas of concern or they could be perfectly normal. If possible, make sure you're working with a radiologist skilled in reading pediatric brain images as these can be very different than adult images.