At one time, scientists believed that people with cognitive reserve had simply been born with bigger brains; that they had more neurons, so if some nerve cells died as a result of Alzheimer's disease or other disease processes, others were waiting to take over. This theory has been disproved —any connection between brain size and cognition is quite subtle.
Imaging studies have provided compelling evidence that brain efficiency, not size, underlies cognitive capacity. Brain scans show that a person learning a new task engages a great deal of the brain or has greater activity in a particular region. As the task becomes familiar, less and less of the brain is needed or used, or the particular brain region becomes less activated. Think about how much concentration it takes to learn a foreign language, and how much easier it becomes over time to speak in that language as the brain becomes more efficient at the task. Dr. Bennett told us, "A good brain is an efficient brain. Cognitive reserve probably has to do with efficiency and the way the brain operates."
A brain with cognitive reserve may have a rich system of "alternative routes" for neural connections. Dr. Bennett compared this to the side streets off a city freeway. "If there is an accident on the freeway, you can get off and use the side streets. You might need to meander around a bit, but you could get where you were going. The side streets weren't built for through traffic, but you can use them for this different purpose. On the other hand, if you're on an isolated two-lane highway and there's an accident, you may have no alternate route." Dr. Bennett speculates that a brain with cognitive reserve may have many more pathways and connections, or "alternate routes," that can rewire themselves when challenged by disease. These may prevent a deficit in memory even though there is pathology in the brain.
A more efficient brain may also help a person perform better on cognitive tests. Processing speed, or how quickly one scans and comprehends information, tends to decline with aging. But according to Dr. Bennett, having a conversation, reading a book or newspaper, listening to the radio, and watching TV all involve processing information, and people who spend more time processing greater varieties of information are found to be better able to maintain youthful scores on tests of processing speed. If a person has better processing resources, it might protect her from expressing Alzheimer's pathology as memory loss.
Previous: Building Cognitive Reserve
Next: The Role of Education
Excerpted from THE ALZHEIMER'S PROJECT: MOMENTUM IN SCIENCE, published by Public Affairs, www.publicaffairsbooks.com.
In This Section
- Building Cognitive Reserve
- Brain Efficiency
- The Role of Education
- Brain Building
- Personality Factors and Social Networks
- Assessing the Potential Benefits of Exercise and Diet
- Exercise and the Brain
- Diet and the Brain
- Developing New Drug Treatments
- Drugs in Development
- Practical Challenges
Momentum in Science: The Supplementary Series
- Understanding and Attacking Alzheimer's 12 min
- How Far We Have Come in Alzheimer's Research 15 min
- Identifying Mild Cognitive Impairment 20 min
- The Role of Genetics in Alzheimer's 12 min
- Advances in Brain Imaging 11 min
- Looking Into the Future of Alzheimer's 6 min
- The Connection Between Insulin and Alzheimer's 21 min
- Inflammation, the Immune System, and Alzheimer's 29 min
- The Benefit of Diet and Exercise in Alzheimer's 16 min
- Cognitive Reserve: What the Religious Orders Study is Revealing about Alzheimer's 20 min
- Searching for an Alzheimer's Cure: The Story of Flurizan 30 min
- The Pulse of Drug Development 15 min
- The DeMoe Family: Early-Onset Alzheimer's Genetics 25 min
- The Nanney/Felts Family: Late-Onset Alzheimer's Genetics 20 min
- The Quest for Biomarkers 17 min
Video: Inside the Brain: Unraveling the Mystery of Alzheimer's Disease
This 4-minute captioned video shows the progression of Alzheimer's disease in the brain.
Inside the Brain: An Interactive Tour
The Brain Tour explains how the brain works and how Alzheimer's affects it.
Alzheimer's Disease: Unraveling the Mystery
This book explains what AD is, describes the main areas in which researchers are working, and highlights new approaches for helping families and friends care for people with AD.
- About The Scientists
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- Rapid advances in our knowledge about AD have led to the development of promising new drugs and treatment strategies. However, before these new strategies can be used in clinical practice, they must be shown to work in people. Advances in prevention and treatment are only possible thanks to volunteers who participate in clinical trials.
- Among those touched by Alzheimer's (excluding self), nearly one-third provide support as a friend or relative, another 3% provide support as a healthcare professional, and the remaining two-thirds provide no support to the person suffering from Alzheimer's. When support is provided, it most often entails emotional support, followed by care-giving support. While small in comparison, more than one person in ten is providing financial support. Read more.