Hang on.

They picked the 'digital generation' (early 20s), and then they forced them to type with right index finger only?

I'm a 45 year old touch typist, and I tried to type above sentence with my right index finger, and basically failed. The unfamiliar motion going against 30 years of muscle memory took all my brain power away from anything resembling creative thought or memorization.

My therapist sent me a study like this few years back when I wanted to write my journal on my laptop :). My comment is the same as back then - the study showing different regions light up is in the wrong order.

1. Do the functional test first - have a big group of people handwrite, and another big group of people type in the way that works for them, and then test memory and understanding.

2. Then, if there's an actual statistical difference, run the imaging tests to see if you can explain why.

As it is, these studies seem just "hey look at different pretty lights". Handwriting for many people in modern age is almost more of an artistic process than typing is; I'm sure it indeed lights up different areas of brain, as would caligraphy or painting - but please, please, start with functional testing first!