White Matter Does Matter
Aging affects us all differently. Depending on lifestyle, diet, and genetics, the aging process can vary greatly. In the same way, our brain changes as we age and has profound effects on mood, memory, and motor function. While there has been a great deal of research in recent years on the changes in the brain of the elderly, in many ways, we have yet to connect all the dots.
Dr. Patrick Sparto, associate professor, Department of Physical Therapy, has been interested in the correlation between changes in the brain in the elderly and the loss of balance, posture, and mobility for several years. He recently began preparing studies he will conduct as part of a new four-year $800,000 National Institutes of Health (NIH) grant. His primary focus is on the study of the degeneration in white matter pathways of the brain.
Sparto initially became interested in the brain while working at a balance disorders clinic. After treating a wide range of older adults, including those with excellent strength and sensation, it occurred to him that the central nervous system had to be responsible for a slow-down in motor skills as people age. As he took a closer look, he felt sure these changes were directly related to the brain. As Sparto began to examine the issue more closely, he honed in on white matter as the root cause; specifically, he hypothesized that as white matter degenerates as we age so does our balance and ability to walk.
Brain Anatomy 101
To truly understand the potential impact of Sparto and his team’s research, it’s important to first know the physiology.Grey matter is a major component of the central nervous system, consisting of nerve cell bodies, glial cells, capillaries, and short nerve cell extensions/processes – axons and dendrites. Its function is to route sensory or motor stimulus to inter-neurons of the central nervous system, the part of the nervous system that consists of the brain and the spinal cord, in order to create a response to the stimulus through chemical synapse activity.
Gray matter structures process information originating in the sensory organs or in other gray matter regions. Put simply, explains Sparto, the grey matter of the brain is where the action happens.
Grey matter is also very involved in regions of the brain that manage muscle control, sensory perceptions like sight and hearing, as well as memory, emotions, and speech.
White matter, on the other hand, is composed of bundles of axons, and is the connector between various grey matter areas, carrying nerve impulses between these areas. Says Sparto, “When one part of the brain communicates with another part, that message is directed along a pathway which, in essencee, is the white matter in our brain.”
Using a common analogy, Sparto says that if our brain were likened to a computer network, the grey matter would be the individual computers while the white matte1r represents the network cables connecting the computers together. It is the white matter that is of particular interest to Sparto.
Dissecting the Problem
Aging can lead to degradation of the white matter in the brain. As the pathways that connect the grey matter areas erode, they lead to the reduction of a host of functions, including cognition, mood regulation, and most notably to Sparto, balance, walking, and other motor skills dealing with mobility.
“We know that a loss or degradation of gray matter leads to a number of conditions, including dementia, Alzheimer’s disease, and Parkinson’s disease, and it seems clear that similar neurological functions also are spawned by a loss of white matter. But the specifics remain unclear,” he posits.
Perhaps the most common disease that affects white matter is Multiple Sclerosis (MS). In this devastating disease, which usually occurs in young adulthood to middle age, white matter is destroyed by inflammation and motor skills decrease over time. The white matter degeneration that occurs in older adults is a different disease process. It is thought to be caused by a reduction in blood flow to certain areas of the brain, in a similar way that clogged arteries reduce blood flow to the heart and extremities.
Sparto continues, “Getting to the bottom of how white matter loss affects us remains one of the big mysteries of the brain – especially as it’s tied to aging.”
Sparto and his team will recruit, meet, and work with 120 adults over the age of 70. There are no specific criteria each person must meet to qualify for the study other than age. Sparto says, “The only criterion is that each person can still move about in the community – it’s pretty inclusive.” Most of the recruitment has been done through the University of Pittsburgh Claude D. Pepper Older Americans Independence Center, but Sparto and the team have also been recruiting participants in the community.
Each individual will be guided through a series of balance and physical therapy-related skill activities and evaluated based on their performance. Then each will be given an MRI to examine the quality of the white matter in the brain. “We’re hoping that a close look at mobility and balance testing compared to white matter changes will lead to some stronger conclusions about the connection between the white matter loss and loss of mobility,” he says.
While the study is still a long way from completion, Sparto feels that the connections between mobility and white matter loss are too strong to ignore. In addition, he believes it is important to understand the relationship because it may impact the rehabilitation process. For instance, other studies have shown that white matter degeneration affects learning – a critical component for any rehabilitation.
Ultimately, helping people to maintain motor skills and balance longer will prevent injuries – keeping them out of the health care system and saving money. But beyond this, there’s the more obvious motivation: helping older people everywhere lead more healthy and productive lives.