I've just seen this cited on Twitter - a scientist who lost her baby to SIDS refused to accept that there wasn't an identifiable reason for her child's death - so she did the research.
It looks like it's a defect in that part of the brain that causes arousal from sleep. Nothing that the parents could have done.
www.biospace.com/article/researchers-answer-how-and-why-infants-die-from-sids/