New imaging technique illuminates memory, aging

Scientists have a new way to read minds — in color and real-time.

A recent Yale University study published in the September issue of the journal Neurobiology of Aging has tracked an age-associated decline in brain receptors related to learning and memory. Using a novel brain imaging technique to follow the concentrations of nicotinic receptors in eight brain regions of 47 living subjects, researchers found that in seven out of the eight regions, these learning-linked receptors decline at a rate of approximately 5 percent per decade. The study was the first to observe receptor decline in living patients, allowing scientists the first look at how the process unfolds over time.

Nicotinic receptors, associated with the reinforcement of smoking addiction, are key participants in neural communication pathways associated with learning and memory. Research based on autopsies of dementia and Alzheimer’s patients has established the role of these receptors in cognitive decline. Yet unlike previous studies in this field, this one employed emerging SPECT imaging technologies, which use gamma rays to generate a three-dimensional image of the brain in order to track receptor decline in living subjects ranging from 18 to 57 years of age.

“In post-mortem studies, it is difficult to be sure that there aren’t conditions surrounding the person’s death that could introduce systematic biases in the results,” said Christopher van Dyck, senior author of the study and a professor of psychiatry and neurobiology, “whereas an in-vivo study allows you to take normal, healthy people and test them cognitively to be sure they are intact for their ages, thus controlling multiple factors that can cause biases.”

The application of SPECT imaging to this field — an approach this paper has advanced — opens up new doors for future medical research in this area. In the near future, scientists hope to use the technique to visualize the effects of medications on the brain over a period of time, said Kelly Cosgrove, co-author of the study and assistant professor of psychiatry at the Yale School of Medicine.

“Normally when you administer medication, you can monitor a behavioral response, but if you also have SPECT imaging, you can see if their brain is actually changing, and if there is a change in receptor concentrations,” she said, “and then medications can be fine-tuned to act on specific sites of the brain.”

Since it introduces a way to track cognitive decline that accompanies aging, the research carries important implications for studying diseases that affect the elderly and for understanding the process of healthy aging, said Guy Eakin, director of research at the American Health Assistance Foundation, a funding source for this study.

Applying these techniques has given us an “effective window into the brain,” a window through which we can monitor the progression of neuro-degenerative conditions like Alzheimer’s disease, he said.

“The next generation of therapeutic successes are going to be predicated on how Alzheimer’s disease is progressing, and there hasn’t been a good way to track this in the past,” he emphasized.

Van Dyck added that, with the newfound understanding of aging this study provides, scientists can even begin to develop treatments that lessen the cognitive decline that accompanies normal aging. As pharmaceutical companies seek treatments for mild cognitive impairment, drugs affecting the concentration of nicotinic receptors could conceivably be engineered.

“A very natural next step would be to ask, ‘Could a nicotinic drug benefit normal age-related memory loss?’ ” he said.

Funding for the study was provided by the American Health Assistance Foundation, the Department of Veteran Affairs and the National Institute of Drug Abuse.

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