In a landmark study published in PLOS One journal researchers at UCLA's Center for Cognitive Neuroscience have found that people with sedentary lifestyle suffered a loss of volume in a particular area of the brain crucial for learning and memory function. Researchers interviewed healthy subjects between the ages of 45 and 75 about their lifestyle particularly the pattern of physical activities. Those participants underwent MRI of the brain and scientists were interested in a particular area of the brain known as Medial Temporal Lobe (The Limbic System). This area is the brain is associated with our mood, emotional response to an event and long-term memory which is composed of all the facts, figures, and names we have ever learned. All of our experiences and conscious memory fall into this category of memory. Amazingly researchers have found that there is relative thinning of this area of the brain in subjects with minimum physical activity in comparison to those who are more active. Every additional hour of average daily sitting was associated with a 2% decrease in the thickness of the medial temporal lobe in this study.
Thinning of Medial Temporal Lobe can lead to cognitive decline and dementia in middle-aged and older adults. Being more physically active can be protective in people at risk for Alzheimer's disease, scientists suggest.
You can read more about the study here:
Sedentary behavior associated with reduced medial temporal lobe thickness in middle-aged and older adults