Anyone who doesn't work out knows how it feels when they finally take some exercise. It's hard and it hurts -- and hurts even more for the next few days. Even seasoned athletes or those who work out regularly, feel the burn if they skip a few weeks. The key is regular exercise with a day or two off every week to rest.
Our minds are the same way. That's why constant stimulation is important. Feeding our brains with new information, lots of data to analyze, and stimulating our senses, is a good thing. In fact, without it, our minds can become as out of shape as our non-exercised bodies.
The term "use it or lose it" is a pretty common statement in senior circles. Older adults are often aware that their brains aren't as stimulated as they used to be, a lot of it to do with the fact that many no longer work and don't face the need to meet deadlines and apply critical thinking all day long. Seniors can also become more isolated, watching a lot of daytime TV (especially in nursing facilities) and not using their brains the way they need to.
During my time working with both older and developmentally disabled adults, the need for brain stimulation was high. Fully-functioning seniors arrived early for Current Events meetings and gave their opinions on war, politics, social security, society and more. Even better, they (and subsequently, I!) had the benefit of decades' worth of comparisons -- from life during the Depression, to the baby and building booms of the 50s, the changing of family dynamics and race and gender rights, into recession periods and back to normal again.
The more people showed up and became regulars, the better they were at voicing their opinions, becoming more informed and wanting more and more information to think about and process. Within a couple of months, the transformations were amazing, with people having discussions among themselves and getting excited about the world around them. Our brains crave information like our bodies crave food and movement.
And it's not just intellectual stimulation that helps. New experiences, using all the senses, are good for our minds.