Came across this article - don't have time at the moment to find the source document. Perhaps someone here could find it for us. Thanks.

Lifelong benefits of early music study.

Don't think this is what the article is referring to (since it seems to focus on longer study of music, and the article refers to only 2 or 3 years - and the focus group is older here) but here is one study: (It's a pdf - if the link doesn't work, try googling Hanna-Plady music)

http://www.apa.org/pubs/journals/releases/neu-25-3-378.pdf

Here's another article similar to the one you posted. Has a link to research journal, but I can't find the correct article.
http://www.latimes.com/health/boostershots/la-heb-mental-benefits-music-lessons-20120821,0,4021820.story?track=rss

Another article referring to John v.d.Brook's OP.
http://blogs.scientificamerican.com/scie...fits-the-brain/
This article cites the source as Journal of Neuroscience. I was not able to retrieve any further study, as I do not have a subscription to the journal.

Good find! Here's the abstract:

Erika Skoe1,2 and Nina Kraus1,2,3,4,5
1Auditory Neuroscience Laboratory, 2Department of Communication Sciences, 3Institute for Neuroscience, 4Department of Neurobiology and Physiology,
and 5Department of Otolaryngology, Northwestern University, Evanston, Illinois 60208

Playing a musical instrument changes the anatomy and function of the brain. But do these changes persist after music training stops? We probed this question by measuring auditory brainstem responses in a cohort of healthy young human adults with varying amounts of past musical training. We show that adults who received formal music instruction as children have more robust brainstem responses to sound than peers who never participated in music lessons and that the magnitude of the response correlates with how recently training ceased. Our results suggest that neural changes accompanying musical training during childhood are retained in adulthood. These findings advance our understanding of long-term neuroplasticity and have general implications for the development of effective auditory training programs.
The Journal of Neuroscience, August 22, 2012 • 32(34):11507–11510

Here's an article from Northwestern University where the research was conducted.

http://www.northwestern.edu/newscenter/stories/2012/08/kraus-childhood-music-training.html

It is not surprising that practicing listening and maintaining attention (as happens in music lessons) enhances listening skills and ability to maintain attention. Interesting to think that these skills once learned, remain with individuals even after they stop music practice.