Go With the Flow: How Increased Brain Blood Flow Improves Memory

Go With the Flow: How Increased Brain Blood Flow Improves Memory

Your brain is the most energy-consuming organ in your entire body. The amount of oxygen your brain needs to get through a normal day is a fifth of your whole body’s supply. The way we get this hefty amount of oxygen to our brains is via the bloodstream following each breathe you take. Your brain has an extensive network of blood vessels to ensure every corner of your cranium is fully fuelled to perform properly and restriction of blood flow to the brain has shown to be detrimental to function. New research has highlighted just how important appropriate blood levels are to our memory formation, and this work could aid research into conditions like memory loss and Alzheimer’s disease. But a big question is, can we improve our brain-blood flow to increase our cognition?

Brain Fuel: Oxygen 

Oxygen is the element of life and our bodies depend on certain levels to function. A healthy blood oxygen level sits at 94%, with levels below this leaving a person at risk of headaches, shortness of breath and heart problems. The way we get oxygen into our blood is through breathing. With every breathe you take, oxygen from the air enters your lungs and travels along the thin branches called bronchioles to the alvioli. This is the point where oxygen diffuses into your blood stream and binds to a molecule called hemoglobin. Each hemoglobin can carry four oxygen molecules and this efficient means of transport is how oxygen reaches all corners of your body.

Your brain requires huge amounts of energy to function due to the chatty nature of the brain cells it holds. As a collective, these cells (neurons) are pretty much in constant communication and their signalling requires a laht of fuel (like 20% of your total bodies oxygen – huge). Oxygen reaches the brain via two main arteries and once within the labyrinth of brain-based blood vessels, oxygen can diffuse into brain cells across cell membranes (no channels or gates required for this top dog!) where it is used to power cellular functions. The areas of oxygen consumption in the brain are dependent on how active the cells in that region are. So for example, if you are making a big decision, areas in the prefrontal cortex will be flooded with oxygen rather than blanket fueling the entire cortex; meaning inactive regions are not taking away resources for when making the choice of a lifetime.

When your brain is deprived of oxygen, it enters a state called ‘hypoxia’ and this can be fatal. Under hypoxia, brain cells can die – the underlying mechanism of neurodegenerative conditions like Alzheimer’s disease and other dementias. Once a brain cell dies, it is very hard to replace meaning any loss of brain tissue can be extremely damaging to an individual. Getting the appropriate levels of oxygen to these cells is therefore a must.

Making Memories: Blood Supply & Cognition

Although we are aware blood flow is increased to active areas of the brain, how does this blood flow impacts cognitive functions like memory? It has been shown that the level of blood perfusion in the brain contributes to cognitive decline in individuals as they age, suggesting this mechanism could be incredibly important in our day-to-day cognition. A new study published in February 2020 explored how the level of blood flow in the brain region vital for making new long-term memories (the hippocampus) affected cognition in healthy controls vs individuals with a condition called cerebral small vessel disease (CSVD) using brain-blood scanning technology. CSVD is a condition which normally occurs as a result of ageing and can precede conditions such as Alzheimer’s disease. CSVD is known to reduce the level of blood flow in the brain, especially in thinner arteries – the main type of vessel supplying the hippocampus with blood. The hippocampus receives blood from two arteries; the posterior cerebral artery and the anterior choroidal artery. In the early 1990s, a study on post mortem tissue characterised the hippocampal blood supply in individuals after death and found people can be supplied with either just one of these arteries or both; highlighting a general difference in the population for how the hippocampus gets it’s fuel to make memories.

The researchers in the 2020 study found individuals with CSVD performed worse in cognitive tests than the control group, with controls with mixed hippocampal blood supplied (i.e. from both arteries) showing an overall better cognition in this set up. These individuals were also found to have a larger hippocampus than people without a mixed blood supply; hinting either the extra blood flow could be maximising their memory formation or the lower blood flow in single-vessel supplied people could reduce their hippocampal volume. Not only did they find mixed-supplied individuals performed better on memory tests, but they had better attention span, language skills and overall cognition. Also, individuals diagnosed with CSVD had a less severe deficit in memory formation if they had a mixed blood supply to their hippocampus compared to those with a single supply. Although the scanning technology may have its limitations in picking up the smallest of vessels, collectively the results of this work suggest an increase blood supply to the hippocampus improves memory and favours the idea that a lack of this supply (in this case mediated by CVSD) may leave hippocampal brain cells vulnerable to cell death.

Can you improve your brain-blood flow?

So it looks like brain blood flow is a really important factor in maintaining healthy cognition, but can we improve this with our lifestyle choices? Although the factors determining whose hippocampus receives blood from a single artery or mixed supply is still unclear, there have been proven ways you can increase your overall brain-blood flow. The major mechanism reported in scientific literature is exercise. It has been suggested that as exercise increases heart rate and blood pressure, this drives an increase in cerebral blood flow. Studies looking at individuals who participated in aerobic exercise over a couple of years had a larger hippocampus and improved spatial memory (i.e. remember where you and other things are) and these changes have been linked to increased blood flow to the hippocampus. Other lifestyle factors such as not smoking, regulating caffeine intake, taking certain vitamins and practicing meditation (de-stressing) have also been linked to increase blood flow to the brain. But of all the lifestyle factors, exercise has the most evidence for getting that blood pumping through your head!

Signing Off

Your brain’s bustling activity requires a lot of blood-based oxygen to keep it healthy and functioning, and now it looks like an increase in this flow could actually be improving cognitive functions like memory. The best way for you to get your brain-blood flow going is to exercise. So the next time you want to skip that run in the rain, just think about your brain!

Brain hugs,

Julia xoxox (@Julia.ravey.science)

For more on brain-blood flow try this review, and this one for how this could effect hippocampus activity. For more brain based information, check out my Youtube and website!