“Linked” is the operative term here.  Earl Miller is quoted in a New York Magazine article about a study that finds less gray matter in people who multitask more.  Earl points out that the study does not necessarily mean that multitasking decreases brain matter.  It could be that people with less gray matter are more impulsive and thus more prone to multitasking.

Tweeting While Watching TV Linked to Fewer Brain Cells

About the Author

The Miller Lab uses experimental and theoretical approaches to study the neural basis of the high-level cognitive functions that underlie complex goal-directed behavior. ekmillerlab.mit.edu