Of all the frightening ways that the SARS-CoV-2 virus affects the body, one of the more insidious is the effect of COVID-19 on the brain. It is now clear that many patients suffering from COVID-19 exhibit neurological symptoms, from loss of smell, to delirium, to an increased risk of stroke.
These effects may be caused by direct viral infection of brain tissue. But growing evidence suggests additional indirect actions triggered via the virus’s infection of epithelial cells and the cardiovascular system, or through the immune system and inflammation, contribute to lasting neurological changes after COVID-19.
(Note: The author is a neuroscientist specializing in how memories are formed, the role of immune cells in the brain and how memory is persistently disrupted after illness and immune activation.)
The immune system and the brain
Many of the symptoms we attribute to an infection are really due to the protective responses of the immune system. A runny nose during a cold is not a direct effect of the virus, but a result of the immune system’s response to the cold virus.
This is also true when it comes to feeling sick. The general malaise, tiredness, fever and social withdrawal are caused by activation of specialized immune cells in the brain, called neuroimmune cells, and signals in the brain.
These changes in brain and behavior, although annoying for our everyday lives, are highly adaptive and immensely beneficial. By resting, you allow the energy-demanding immune response to do its thing.
A fever makes the body less hospitable to viruses and increases the efficiency of the immune system. Social withdrawal may help decrease spread of the virus.
In addition to changing behavior and regulating physiological responses during illness, the specialized immune system in the brain also plays a number of other roles.
It has recently become clear that the neuroimmune cells that sit at the connections between brain cells (synapses), which provide energy and minute quantities of inflammatory signals, are essential for normal memory formation.
Unfortunately, this also provides a way in which illnesses like COVID-19 can cause both acute neurological symptoms and long-lasting issues in the brain.
During illness and inflammation, the specialized immune cells in the brain become activated, spewing vast quantities of inflammatory signals, and modifying how they communicate with neurons.
Because COVID-19 involves a massive release of inflammatory signals, the impact of this disease on memory is particularly interesting to me. That is because there are both short-term effects on cognition (delirium), and the potential for long-lasting changes in memory, attention and cognition.
There is also an increased risk for cognitive decline and dementia, including Alzheimer’s disease, during aging.
How does inflammation exert long-lasting effects on memory?
If activation of neuroimmune cells is limited to the duration of the illness, then how can inflammation cause long-lasting memory deficits or increase the risk of cognitive decline?
Both the brain and the immune system have specifically evolved to change as a consequence of experience, in order to neutralize danger and maximize survival. In the brain, changes in connections between neurons allow us to store memories and rapidly change behavior to escape threat or seek food or social opportunities.
Does COVID-19 increase risk for cognitive decline?
It will be many years before we know whether the COVID-19 infection causes an increased risk for cognitive decline or Alzheimer’s disease. But this risk may be decreased or mitigated through prevention and treatment of COVID-19.
There are several drugs that have proven to be effective in reducing inflammation, however, drugs can have serious side effects and are best used as a temporary solution. For long term, permanent results, a better therapy for the brain is neurofeedback.
Neurofeedback is a modern computer-based technology that can help reconnect neural pathways and restore healthy brainwaves. It may effectively reverse the effects of inflammation on the brain resulting from a COVID infection. The process is safe, non-invasive, drug free and sessions are enjoyable. You can learn more about neurofeedback on this site.
COVID-19 will continue to impact health and well-being long after the pandemic is over. As such, it will be critical to continue to assess the effects of COVID-19 illness in vulnerability to later cognitive decline and dementias.
