KCRW is holding its pledge drive this week. And it turns out, there’s a whole world of brain chemistry and brain science behind that fuzzy feeling you get when you donate. We look at a case study: A man in Brazil used to be a thrifty H.R. executive who loved to save as much as he could. But one day, he woke up with the insatiable urge to give. His overnight generosity ended up being so extreme, it cost him all the comforts of his life, yet he was happier than he’d ever been. What caused all this? A stroke. We look at the neurology of generosity.