Margarita Tartakovski on PsychCentral says,
Information is merely a click — or, more accurately, a Google search — away. Depending on your query, there’s likely at least a dozen, if not hundreds, of blogs on the topic, a similar number of books and many more articles.
This is a good thing, but it also can overburden our brains.
According to Lucy Jo Palladino, Ph.D, a psychologist and author of Find Your Focus Zone: An Effective New Plan to Defeat Distraction and Overload, “Information overload occurs when a person is exposed to more information than the brain can process at one time.”
Alvin Toffler actually coined the term in 1970 in his book Future Shock. As more and more people started using the Web, “information overload” became a popular phrase to describe how we felt about going online, Palladino said.
According to neuroscientists, the more accurate term is “cognitive overload,” she said. That’s “because the brain can process vast amounts of information depending on the form in which it’s presented,”
According to Professor Torkel Klingberg, MD, PhD (2009), the brain can suffer from information overload, and he gives some examples of what he is talking about.
Our brains have limited capacity for processing information. This book is an attempt to understand why this is so, what effect it has on our everyday lives, and how we can stretch these limits with mental exercise......In his article "Overloaded Circuits: Why Smart People Underperform," psychiatrist Edward Hallowell coins the term "attention deficit trait" to characterize the situation.
From these articles, and articles linked within these articles, I would say that there are times that the brain needs rest at times in-between mental activities, in order to process things learnt, but the periods of rest needed can vary depending on how the activity taxes the brain, and how much it is used to dealing with the information.