“It has been proved the older we get that the elasticity of the brain decreases, there for we must make the most of our youth to learn a second language. In the early stages of bilingual subjects, both languages are integrated in the same cortical region of the brain, to be more exact in the area known as Broca witch functions are linked to speech production. Futher functional studies have expressed that language tasks is more fluid when the subject is in an early stage of development. In the more matured subjects, however, this is not so as further functional studies have identified  that these subjects register the different languages in separate patterns in the Broca`s area of the brain” (Villarroel, 2003).

Some docs (in spanish):

• Procesos de Adquisición de Segundas lenguas durante la infancia (http://www.waece.org/biblioteca/pdfs/d047.pdf)
• Las ventajas de ser bilingüe (http://www.elmundo.es/elmundosalud/2011/02/18/neurociencia/1298046214.html)
• Educación bilingúe (http://educacion-bilingue.com/)
• Libros bilingües (http://educacion-bilingue.com/libros-bilingues/)
• Cuidadoras bilingües (http://www.nytimes.com/2010/08/19/nyregion/19bilingual.html?_r=1&WT.mc_id=NY-SM-E-FB-SM-LIN-WBS-081910-NYT-NA&WT.mc_ev=click)