Adam, yeah. I’ve done both TM in the distant past (early 1980’s) and then switched over to Vipassana / mindfulness in the mid 80’s; so understand both approaches. And Fred Travis’ research is impeccable.
You might initially think that TM is a ‘concentrative’ / mantra / focused attention style practice. But that is not actually the case. It’s much more subtle than that. The mantra or phrase being used is induced in a manner that is as subtle and gentle as is possible. (It is not “shouted” out mentally.)
This emphasis on subtle-ness and very fine awareness actually puts the practitioner in a place in-between a pervasive sense of consciousness that is universal / everywhere – and the ‘intention’ being softly broadcast. Thus has a quality of ‘inducing’ that intention into the larger field, making oneself a part of that larger field.
Regarding how to connect frequency bands to the neurofeedback. That is the ‘art’ form of neurofeedback. I’d again point to the Meditation and Neurofeedback paper. The feedback then is more of a guidepost that arises periodically to keep you on track with your meditation style. It’s not “doing” the meditation for you. Such as the idea of alerting you when your mind is wandering (which would likely be increased beta activity).
Do note that increasing frontal midline theta would be contraindicated in situations where a person already has difficulty in concentrating or focusing, as in ADD / ADHD. You may find Jay Gunkelman’s phenotype paper helpful in delineating some common patterns.
Jay’s 2005 phenotype paper,
Brief html summary,