Interactive Metronome uses a steady metronome beat and the timing is measured in ms before or after the beat as you tap out the beat with either hand, foot or combination hand/foot. It is not a pattern of rhythm but rather a constant steady beat. I think this is what the study referred to was assessing. I don't believe they were referring to keeping a musical beat with varying timing and length beat, rests, etc.
When I use IM training I see improvements in general processing skills including areas of motor coordination, visual motor integration, listening and auditory figure-ground skills, ability to follow verbal directions and improvements in reading comprehension and even math skills (often from better spatial processing). I'm assuming that the IM newsletter referenced this study as it supports the idea that improving basic timing ability might be able to boost intellectual processing.
I've had several very intelligent people who also have dyspraxia or similar difficulties do the IM training with me. They have all commented that they felt "more organized" and that they were better able to multi-task and process information better in the ways that were previously more difficult (ie: someone who needed things visually could now process auditory info better).
