Researchers in the UK have found that inflammation in the brain following an infection can adversely affect how spatial memories are formed.
This new study, which is published in the journal Biological Psychiatry, builds on existing research linking infections to decreased cognitive function.
Study leader Dr. Neil Harrison, from the Brighton and Sussex Medical School, says:
"We have known for some time that severe infections can lead to long-term cognitive impairment in the elderly. Infections are also a common trigger for acute decline in function in patients with dementia and Alzheimer's disease."
Dr. Harrison and his team administered shots of either benign salty water or a typhoid vaccine to 20 healthy participants.
They used fluorodeoxyglucose (FDG)-positron emission tomography (PET) to scan the brains of the participants before and after the injection, measuring the inflammation occurring in the participants' brains.
The spatial memory of the participants was tested after each scan using a series of memory-based virtual reality tasks.
The participants did not perform as well in spatial memory tasks following a reduction in glucose metabolism.
From the FDG-PET scans, the researchers observed that following inflammation there was a reduction in glucose metabolism within an area of the brain called the medial temporal lobe (MTL).
The MTL is the brain's "memory center," and the change in metabolism within it seemed to directly relate to spatial memory performance. When the participants attempted the spatial memory tasks following this change in glucose metabolism, they performed less well.
Spatial memories form a "cognitive map" that allow us to navigate our surroundings. Although the reduced glucose metabolism caused by the inflammation resulted in lower spatial memory test scores for the participants, their "procedural memory" - memory of how to perform particular types of action - was not affected.
Even mild infections can cause spatial memory impairment
"This study suggests that catching a cold or the flu, which leads to inflammation in the brain, could impair our memory," Dr. Harrison says, although he points out that there are unlikely to be long-term adverse effects from infections in young and healthy people.
But these findings may be significant for elderly people. The team wants to investigate what role inflammation may play in dementia and how infections such as flu may affect its progress.
Dr. Harrison hopes that his team's findings will lead to the development of new drugs that could treat dementia by targeting the immune system.
"Our findings suggest that the brain's memory circuits are particularly sensitive to inflammation and help clarify the association between inflammation and decline in dementia," says Dr. Harrison. "If we can control levels of inflammation, we may be able to reduce the rate of decline in patients' cognition."
Recently, Medical News Today reported on a study suggesting that signs of cognitive decline in the elderly may not necessarily be symptoms of dementia. Instead, the researchers posit the theory that, as memories and knowledge naturally accumulate in the brain over time, this causes a reduction in "processing capacity," resulting in information taking longer to process.