People often associate Alzheimer’s disease with aging, but the brain transformations linked to it start much earlier—typically around our thirties.
The first signs involve a disrupted form of a protein known as tau, which accumulates in a small brain area responsible for sleep and attention, called the locus coeruleus. This tau eventually spreads throughout the brain.
However, having tau tangles doesn’t necessarily mean someone has Alzheimer’s; many people experience this to varying extents. Because these changes initiate in the locus coeruleus, some researchers view it as a warning sign for the disease.
Current studies are looking into whether halting or slowing the formation of tau tangles in this area might impact the disease’s progression and help maintain cognitive abilities as we age.
Recent research from my team and others is delving into the potential of a therapy called vagus nerve stimulation. This treatment is currently used for several health issues, and it may help keep the locus coeruleus functioning optimally.
The locus coeruleus and Alzheimer’s disease
The locus coeruleus resides in the brain stem, the brain’s lowest part. Its name, which means “blue spot,” comes from a pigment called neuromelanin produced by its cells.
This tiny spot plays an essential role in various basic human functions. It generates nearly all of the brain’s norepinephrine, a critical neurotransmitter for sleep, alertness, focus, learning, and even immune response.
Additionally, it receives signals from nerves throughout the body, including the vagus nerve, which transmits information between the brain and vital organs.
My research examines the structure of this brain region, the way nerve cells communicate there, and how it connects with other areas of the brain. I’m also interested in how these characteristics evolve with age and influence memory and cognition.
Studies indicate that starting in middle age, nerve cells in the locus coeruleus can suffer damage due to tau buildup, which may correlate with memory declines. This tau accumulation, cell loss, and dysfunction in the locus coeruleus often precede and predict Alzheimer’s diagnosis.
This insight has led researchers to suggest that maintaining the health of the locus coeruleus could help protect the rest of the brain as well.
Vagus nerve stimulation and brain health
The vagus nerve acts as a communication line between the brain and organs in the chest and abdomen, like the heart and intestines. It helps the brain monitor and manage essential bodily functions, promoting digestion and cellular repair.
During the ’80s and ’90s, researchers found that stimulating the vagus nerve could reduce epilepsy symptoms and often had additional benefits, including improvements in mood and cognitive function.
Currently, the Food and Drug Administration has approved vagus nerve stimulation for not only epilepsy but also for migraines and depression, and it plays a role in stroke rehabilitation.
Vagus nerve stimulation for epilepsy and depression typically involves implanting an electrical stimulator in the left side of the chest, where the vagus nerve runs. Noninvasive options exist as well, providing gentle electrical pulses to points on the neck or ear where the nerve is close to the surface.
Even before acknowledging the link between the locus coeruleus and Alzheimer’s, researchers speculated that vagus nerve stimulation could benefit mood and cognition for those with the disease. This potential benefit is likely due to its role in increasing norepinephrine levels in the brain—a neurotransmitter often found at low levels in Alzheimer’s patients.
Keeping the pace
Neuroscientists still don’t fully understand how vagus nerve stimulation might positively affect the brain. One prominent theory is that it helps modulate nerve cell activity in the locus coeruleus, allowing it to operate effectively.
If locus coeruleus activity is too high, it could lead to excessive alertness, which in turn might result in stress or panic. Interestingly, overactivity in this area can be linked to symptoms found in post-traumatic stress disorder. On the other hand, insufficient activity could contribute to depression or memory issues.
Some types of vagus nerve stimulation don’t necessarily increase or decrease activity in the locus coeruleus. Instead, they seem to influence how often its neurons fire. Other types have been noted to raise norepinephrine levels in the brains of rats, which might also explain how vagus nerve stimulation helps with epilepsy.
These varied findings have led researchers to propose that vagus nerve stimulation serves as an effective regulator for the locus coeruleus, helping it maintain an optimal activity level.
Can vagus nerve stimulation counter memory loss?
There’s emerging evidence that vagus nerve stimulation could benefit the aging brain.
Some studies suggest that vagus nerve stimulation can prevent memory deterioration and even improve cognitive function in individuals experiencing mild cognitive impairment or early-stage Alzheimer’s.
In one trial involving 52 participants aged 55 to 75 with mild cognitive impairment, significant enhancements in memory and cognitive performance were observed after daily vagus nerve stimulation sessions lasting an hour, five days a week, for about six months.
Further research involving healthy adults around the age of 60—and even younger adults aged 18 to 25—has shown various memory improvements following just one session of vagus nerve stimulation.
This work remains quite preliminary but opens up promising avenues for addressing some distressing symptoms linked to Alzheimer’s and the aging process.
