A rat called Puh. Image: Alexey Krasavin (CC-BY 2.0)

Stimulating memories

Deep brain stimulation can improve the performance of middle-aged rats in memory tests.

Memory loss in older people is a serious and widespread problem that affects up to half of those over the age of 85. It is a key symptom of dementia, but despite the growing impact of this disease on society, there are no treatments currently available that can effectively stop or delay the progression of the symptoms.

One therapy that may reduce memory loss is called deep brain stimulation. Electrodes are implanted into the brain and used to stimulate brain cells in particular areas of the brain to alter mental and emotional processes. Deep brain stimulation is already used to treat Parkinson’s disease, depression and other conditions that affect how the brain works.

Albert Liu and co-workers studied the effect of deep brain stimulation on memory in rats. The experiments show that middle-aged rats performed less well in short- and long-term memory tests than young rats. Next, Liu and co-workers investigated whether deep brain stimulation could improve memory in the middle-aged rats. The electrodes were positioned to stimulate a region near the front of the brain called the ventromedial prefrontal cortex; this region is important for the formation and recall of memories. Liu and co-workers then gave the rats a series of memory tasks that tested their recall after 90 minutes (to test their short-term memory), and after 24 hours (to test long-term memory).

The experiments reveal that a brief stimulation of brain cells in this region of the brain improved the rats’ short-term memory, but not their long-term memory. However, more sustained stimulation of this region of the brain improved both the short-term and long-term memory of the rats. Furthermore, deep brain stimulation led to the formation of new brain cells in another region of the brain called the hippocampus, which is also involved in memory. The hippocampus had not been in direct contact with the electrodes so the increase in brain cells was due to its connections with the stimulated ventromedial prefrontal cortex.

These findings suggest that deep brain stimulation of the ventromedial prefrontal cortex has the potential to be developed into a therapy to treat dementia and other conditions that lead to memory loss in humans.

To find out more

Read the eLife research paper on which this eLife digest is based:“Ventromedial prefrontal cortex stimulation enhances memory and hippocampal neurogenesis in the middle-aged rats” (March 13, 2015).
eLife is an open-access journal that publishes outstanding research in the life sciences and biomedicine.
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