Part of the brain’s normal process of development, as well as healthy maintenance throughout life, involves synaptic pruning. Think of it like reallocating resources: cells called microglia roam throughout the brain, cleaning up waste products and trimming connections that aren’t needed. This way the brain can maintain optimum efficiency. This is one of the critical features of neuroplasticity.
This process is especially critical in babies and young children, as they have far more connections in their brains than do adults. Brain development is sort of like chiseling a sculpture out of raw stone: from many connections, the microglia help the baby to chisel away those that are not useful, leaving only those that are. One theory of autism involves malfunctioning of microglia: that is, connections that should be pruned away, aren’t (1, 2).
But impaired neuroplasticity plays a significant role in other forms of brain injury as well—including Alzheimer’s Disease, Traumatic Brain Injury, and cumulative brain injury from repeated mild head trauma.
Inflammation —> Damaged Microglia
There’s a bit of a “Catch 22” here, as you might guess from the different causative factors involved in head trauma versus diseases such as autism or Alzheimer’s. On one hand, if inflammation arises in the body and crosses the Blood Brain Barrier, this can lead to damaged microglia and impaired synaptic pruning.
Inflammation generally, or chronic excess of such pro-inflammatory cytokines as IL-2, IL-6, and TNF-alpha, are associated with damage to the central nervous system and decreased neuroplasticity. We’re finding more and more that such damage might have its origin in the gut, via what is now called the “Gut-Brain Axis”: metabolic endotoxemia that can arise from leaky gut syndrome is often involved in neurodegeneration.
This study specifically shows that propionic acid, a byproduct of bacteria in the clostridia family, leads to activated (inflamed) microglia. Interestingly, this study also shows that inflammatory cytokines slow down gut motility, which can easily lead to SIBO, perpetuating the inflammatory process.
Damaged Microglia Also —> Inflammation
I mentioned a “Catch 22”: the other side of it is that microglia may be damaged directly, which will then result in higher levels of inflammation. This study shows that microglia can develop an exaggerated inflammatory response secondary to trauma. (And again, as this study shows, inflammatory cytokines can slow gut motility, leading to SIBO and perpetuating inflammation. Yet another Catch 22.)
Either way, the result is impaired neuroplasticity.
Essential Fatty Acids Can Calm Neuroinflammation
The good news is, studies also show that something as simple as essential fatty acids, particularly DHA (docosahexaenoic acid), can help decrease neuroinflammation, and in turn improve microglia function.
This study shows that DHA can restore microglia function after TBI (traumatic brain injury).
This study suggests that essential fatty acids can have similar effects on other neurodegenerative diseases, such as Alzheimer’s Disease — as well as on other psychiatric conditions such as bipolar disorder and ADD/ADHD.
It’s a great idea for pretty much everyone to take an Essential Fatty Acid supplement daily, and to stay away from omega 6 fatty acids. But if you suffer from any kind of neurodegenerative illness, it might be a good idea to check your O3:O6 ratio to make sure you don’t need to get more aggressive than that.