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Contact:Andrew Porterfield, (949) 824-3969, [email protected]
UC IRVINE STUDY SHOWS WHY SOME PEOPLE HAVE BETTER LONG-TERM MEMORY THAN OTHERS
Study Contributes to Understanding of How Memories Are Stored in Brain
Irvine, Calif. - Some people can remember simple facts better than others because the area of their brains involved in processing these memories is more active at the time of learning, a UC Irvine study shows.
The study provides new insight into how long-term memory works and confirms recent studies that provide the most detailed maps to date of specific areas in the brain responsible for processing memories.
The findings, which appear in the Nov. 24 Proceedings of the National Academy of Sciences, eventually could result in more effective drugs and therapies to improve memory.
UCI College of Medicine researchers Dr. Michael Alkire, Richard Haier and James Fallon, and Lawrence Cahill of UCI's Center for the Neurobiology of Learning and Memory, found that a simple test of long-term memory produced different levels of metabolic activity in the brain, and that the activity levels predicted accurately how well memories are stored. The researchers also found that most of this activity took place in a section of the brain's cerebral cortex called the para-hippocampal gyrus. The para-hippocampal gyrus is a part of the cerebral cortex located near the ear, and is so named because it sits next to another area of the brain important in memory, the hippocampus.
"This is one of the first studies to show that the amount of brain activity in a particular area is related to how well the memory is retained. Someday, we hope these findings will result in new ways to aid memory retention, including drugs that control specific neurotransmitters working within the memory-enhancing parts of the brain," Alkire said.
The researchers found that the para-hippocampal gyrus was highly activated in test participants with better memories of non-emotionally arousing information. In 1996, the researchers received international attention for a study published in the Proceedings of the National Academy of Sciences that demonstrated that long-term memory of emotionally arousing events was associated with increased activity in a brain structure called the amygdala (pronounced "ah-MIG-duh-luh"), located near the para-hippocampal gyrus.
In the new study, they found that, while the para-hippocampal gyrus showed increased activity related to recalling non-emotional information, the amygdala showed none, providing further support for the view that the amygdala processes only the memories of emotionally arousing events.
"By seeing where long-term, non-emotional memory is handled, and where it isn't, we can create a more detailed map of how the brain deals with the memories, emotions, behaviors and attitudes that make us distinctly human," Alkire said.
The researchers traced brain activity using a positron emission tomography (PET) scanner, which allowed them to follow radioactively labeled sugar as it traveled to different parts of the brain, where it was taken up by nerve cells as food. More active parts of the brain metabolized more of the radioactive sugar, which showed up more often on the PET scan.
Eight participants were scanned as they listened to a list of simple, unrelated words such as "accept," "garden" and "purple." Twenty-four hours later, the same participants attempted to recall as many of the words as they could. The participants remembered between 20 percent and 90 percent of the words. Those participants whose brains had shown the most initial activity within the para-hippocampal gyrus could remember more words a day later than those whose brains had less activity.
"This latest study not only confirms recent work by other researchers that shows the areas involved when new memories are being created, but shows that long-term memories of routine tasks are processed in different areas than short-term and emotional memories," Cahill said.
The UCI researchers have been working for several years on understanding how disease, emotions, anesthesia and other common stimuli affect memory and consciousness in the brain. Future studies will compare activity within the para-hippocampal gyrus and amygdala with other areas of the brain involved with memory, which should lead to even more detailed mapping of areas that handle different types of memory.
"The more information you get on where memory is handled, the more you can manipulate neurotransmitters in very specific areas and make specific changes in behavior," Cahill said.
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