Haven't read the book but I've always contended that the rise in electrical energy and the proliferation of chemicals in our food coupled with sensory overload have something to do with neurological dysfunction.
And yes, history does show that right and left brain alternate, if that's how they're terming it. Throughout history, when there is a rise in science, at some point, people tire of it and begin to take a strong interest in the arts again and the reverse.