Subgoal 2: Maintain and Enhance Brain Function, Cognition, and Other Behaviors

In the past, significant loss in the ability to remember, learn, think, and reason-skills known collectively as cognition-were considered a normal part of aging. Now we know that most people remain both relatively alert and mentally able as they age and that severe cognitive loss is the result of disease. Without disease, older people can maintain mental acuity by taking part in activities that stimulate the mind and the body. Remaining actively and productively engaged in one's community and social group, and leading a healthy lifestyle are important in maintaining optimum brain function. Severe mental decline is not inevitable; the aged brain maintains the capacity to make new connections, absorb new information, and acquire new skills.

Some losses in memory and other aspects of cognition do occur with advancing age. Being able to distinguish between normal changes and the abnormal changes of disease is crucial for diagnosing disease and for designing strategies to maintain cognitive function. This knowledge is being developed by studying changes in areas of the brain involved in learning and memory, such as the hippocampus.

New methods of imaging the activity of specific regions of the brain allow scientists to see the brain at work during cognitive tasks and thus help identify age-related neural changes and ways in which the older brain attempts to compensate in order to maintain optimal cognitive function.

Knowing how the brain ages provides important information on which to base strategies for maintaining and enhancing cognition through biological and behavioral interventions. For example, it was recently shown that some new neurons form in adulthood in certain regions of the brain, contrary to prevailing beliefs. This advance presents the possibility that methods could be found to compensate for neuron loss and cognitive decline from disease or traumatic injury. Behavioral strategies are also being developed to retain cognitive function.

To maintain cognition and avoid disease and disability, research is needed to:

1. Characterize changes that occur with normal brain aging and with neurodegenerative disorders
   
   Scientists are making significant progress in understanding what constitutes normal brain aging. Contrary to earlier beliefs, decline in neuron number is not significantly involved in normal brain aging. In fact, recent evidence indicates that the older brain is capable of generating new nerve cells, particularly in a region of the brain important for acquiring and processing information, the hippocampus. These findings have turned researchers' attention to the investigation of more subtle neural changes with age: selective neuronal loss or dysfunction with implications for memory and other functions, remodeling of synapses (where nerve cells communicate), reduction in or dysfunction of neuronal connections, minor brain atrophy, and changes in responses of non-neuronal cells (such as glial cells) involved in neuron survival and brain plasticity. Modest decline also has been detected in the chemicals that conduct nerve signals, such as acetylcholine, and in communication among brain regions.
   
   In neurodegenerative disorders, neuronal cell death and dysfunction are widespread. Gene mutations result in altered proteins that cause or contribute to disease. Abnormally-folded, insoluble proteins may accumulate in the brains of patients. These changes are often correlated with the proteins' losing function or becoming toxic, leading to death of neurons. Neuronal death may also occur because of inappropriate activation of a signaling pathway for "cell suicide," known as apoptosis. Synapses decrease in vulnerable areas of the brain. Glial cells may become activated, contributing to inflammation. Further characterization of these pathologic changes will enhance our basic knowledge of altered neural function in the elderly and aid the development of appropriate treatments.
    
2. Characterize normal cognitive and brain function of the oldest-old
   
   Very little is known about the changes in brain function that normally take place in the fastest growing segment of the U.S. population-the oldest-old-those individuals aged 85 years and older. In the absence of disease, many of these individuals continue to lead healthy and productive lives even into extreme old age. It is important to distinguish normal aging-related changes from disease in this group in order to find ways to maintain function as long as possible.
   
   Another growing segment of the population is made up of centenarians, those individuals aged 100 or more. Scientists are studying this group to understand what factors or behaviors contribute to their long lives, especially among those who continue to function well.
    
3. Understand the interaction of gene, molecular, cellular, and environmental factors for optimal cognitive function
   
   Promoting the full potential of the central and peripheral nervous systems depends on developing the brain optimally in early life, continuing cognitive activity to maintain function, and stimulating the brain to compensate for cell death and injury. More needs to be learned about neurotrophic factors, protein signals that promote growth and survival, and their impact on stimulating the brain to adapt to declines in function. Research is underway to find the genetic, cellular, and molecular basis of functional decrements in nervous system aging. Strategies must be developed to minimize environmental factors, such as oxidative stress and toxins that degrade function. New leads for optimal nutrition for nervous system development early in life and maintenance in later life should be identified to improve cognitive processes and delay age-related mild cognitive impairment.
    
4. Enhance learning, attention, memory, language skills, reasoning, judgment, decision-making, and other aspects of cognition.
   
   Interventions designed to improve cognitive or related perceptual abilities and skills can reduce the need for formal care and hospitalization, and maintain independence for older people. Everyday tasks that use inductive reasoning can be taught by demonstrating strategies to identify rules or patterns or by practicing problem solving. These tasks include ensuring that older persons can complete a medication schedule chart or load a pill reminder, understand schedules, follow menus, engage in work or leisure activities that involve following a pattern or rule, and perform repetitive exercise routines. Regular challenges of the brain can help retain cognitive abilities and mental acuity. Research with such practical applications for improving everyday functioning will be encouraged.