Sensitive periods for white matter plasticity and reading intervention

As a child matures, some brain circuits stabilize while others remain plastic. However, the literature on maturational changes in the brain’s capacity for experience-dependent plasticity is primarily based on experiments in animals that mature over dramatically different time-scales than humans. Moreover, while principles of plasticity for sensory and motor systems might be conserved across species, the myriad of late-developing and uniquely human cognitive functions such as literacy cannot be studied with animal models. Here we use an intensive reading intervention program, in combination with longitudinal diffusion MRI measurements in school-aged children with dyslexia, to investigate the sensitive period for white matter plasticity and literacy learning. We find that the intervention induces large-scale changes in white matter diffusion properties, and improvements in reading scores, but that the magnitude and time-course of plasticity does not depend on the subject’s age. Thus, we conclude that, for the intensive, one-on-one reading intervention program employed here, if a sensitive period exists, it does not end before middle school.