A new University of Florida study has found significant attention deficits in middle-aged rats, which researchers have traced to a nerve cell receptor that is necessary for learning and memory. As aging makes the receptor less functional, learning some tasks or remembering certain things gets much more difficult, researchers found.
But memory problems aren’t just the bane of the elderly. In laboratory tests, cognitive skills and memory declined significantly among some rats that were middle-aged – roughly equivalent to an adult in his or her 50s. The research was published in The Journal of Neuroscience.
Researchers already knew the nerve cell receptor’s function affected the hippocampus, a part of the brain associated with long-term memory. In the current study, they wanted to know how the nerve cell receptor’s diminished function would affect the prefrontal cortex, the part of the brain that drives cognitive skills such as attention, problem solving and working memory.
“At middle age, certain cognitive functions are more at risk than initially thought,” said Thomas C. Foster, Ph.D, a professor in the UF College of Medicine’s department of neuroscience and chair for research on cognitive aging and memory at UF’s Evelyn F. and William L. McKnight Brain Institute.
That means struggling with everyday issues – misplacing car keys or losing a train of thought – might have more significance in middle age.
To test those theories, researchers measured whether trained rats responded correctly and promptly to a brief flash of light. The rats were rewarded with food when they correctly chose the illuminated hole from among five openings within a set amount of time. The middle-aged rats were much less accurate than the younger ones, and more than twice as likely to not make a choice at all when the task was made more difficult, researchers found.
So what does that mean for humans? The results point to a possible reason why it’s harder for older people to learn new information when a lot of attention is required, according to Foster.
“This gives validation to the theory that certain aspects of cognitive decline start in middle age,” he said.
Foster and two other UF researchers also wanted to know why the nerve cell receptor, known as NMDA, was losing some if its function. Several parts of the brain, including the hippocampus and prefrontal cortex, rely on the receptor for functions that include memory, decision-making and attention. Aging can intensify the production of harmful free radicals that cause oxidative stress. That process changes the shape and function of the nerve cell receptor, which leads to cognitive problems, researchers found.
Without an active, properly functioning nerve cell receptor, Foster said, it’s hard to learn new things. In one part of the brain, keeping that activity going is what allows a person to maintain his or her attention.
That helps explain why some middle-aged animals begin to show signs of struggle with memory issues and some cognitive tasks. Age-related cognitive decline actually starts when people are in their 20s but doesn’t usually become noticeable for several more decades, Foster said.
“If you’re going to learn something new when you’re in your 50s or 60s and you’re going to have to pay attention, it’s going to be a bit tougher,” he said. “When we get into our 50s, our eyes start to go. There are a lot of things that start to go, and cognitive function is a part of that.”
Impaired Attention and Synaptic Senescence of the Prefrontal Cortex Involves Redox Regulation of NMDA Receptors, Michael Guidi, Ashok Kumar, and Thomas C. Foster, The Journal of Neuroscience, doi: 10.1523/JNEUROSCI.3523-14.2015, published 4 March 2015.
Source: University of Florida