Learning About Cognitive Aging
Improvements in public health, medical care, nutrition, and living standards mean that we are now living longer than ever. Many older adults enjoy active, productive lives, but they also face the risk of cognitive and memory problems.
This challenge has provided a major impetus for research into healthy cognitive aging. Scientists want to know how and why some people remain cognitively healthy all their lives while others do not. Answers to these questions also can help researchers understand what goes wrong in AD and other neurodegenerative diseases and can point the way to interventions that might maintain successful brain and cognitive aging.
- Working memory is an important kind of short-term memory that maintains information in a temporary “buffer” that can be continually updated as needed. This type of memory is important for cognitive and emotional function, allowing us to inhibit inappropriate actions and plan future actions. Working memory appears to depend on recurring activity in networks involving neurons in the front part of the brain (the prefrontal cortex). This activity allows neurons to continue firing during periods of delay when the stimulus or event to be remembered is not present in the environment, thus maintaining a representation of the information over time, even in the face of distracting stimuli or information. With increasing age, working-memory deficits become a consistent feature of declines in cognitive performance.
Investigators at the Yale University School of Medicine conducted an extensive series of experiments in rats and nonhuman primates and found that stimulating neuronal receptors in the prefrontal cortex improved working memory (Wang et al., 2007). They also found that weakened connections within neuronal networks in this brain region may underlie some of the cognitive deficits seen in older adults.
- A research team at the University of Kentucky and Memory Pharmaceuticals Corporation in Montvale, New Jersey, took another approach to studying cognitive aging (Rowe WB et al., 2007). This study in rats combined analyses of changes in expression of many genes with behavioral testing to determine gene changes that are selectively associated with age-related cognitive dysfunction in the hippocampus. Results showed clear differences in expression of genes that occurred in the brain between the cognitively impaired and cognitively healthy rats, suggesting a model for age-related cognitive impairment. In this model, if decreases in expression of genes important for the use of glucose and in energy production by cells that support neuronal function were coupled with deficiencies in neuronal energy production, neurons would be unable to trigger activity that enables plasticity and memory formation in response to learning tasks. In this model, these deficiencies also might generate signals that activate harmful pathways, further disrupting cognitive processes.
- The multi-site Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) clinical trial, funded by NIA and the National Institute of Nursing Research (NINR), is designed to test the effects of brief cognitive training in older adults. In one component, researchers at the Indiana University School of Medicine examined the effects of cognitive training on participants who exhibited declines in cognitive function (Unverzagt et al., 2007). Participants received training in memory, reasoning, or speed of processing of visual information.
Compared with a control group that received no training, the participants who received the memory training and had normal memory at the start of the study showed significant improvement in memorization skills. Among participants with pre-existing declines in memory function, however, those in the memory training group showed no benefit. Those who received the reasoning or the speed-of-processing training showed improvement comparable to participants with normal memory.
These findings suggest that older adults with pre-existing mild memory impairment may not benefit from memory training as much as those with normal memory function, but they benefit just as much from certain forms of cognitive training that do not rely on memorization. This training may be able to improve the ability of older adults to maintain skills that allow them to carry out daily tasks and lead a higher quality of life.
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