John M. Talmadge, M.D.

A Blog Covering Many Topics

New Brain Discovery? Lymph!

Although we don't know for certain that new treatments are just over the horizon, here's some potentially exciting news. Scientists at the University of Virginia have discovered previously unknown lymphatic vessels in the outer layers of the brain. These vessels appeared to link the brain and spinal cord with the rest of the body’s immune system. This study used mice and human samples, vessel structure was investigated in the mice, and the observations followed up in the human samples. This was an animal study using mice to investigate the structure and function of lymphatic vessels in the brain. In fact, this story has been circulating for awhile, but recently it's been highlighted in several stories. The good news is that this may mean that the original studies are standing up to scrutiny by other scientists.

The discovery may require a reassessment of our assumptions about lymph drainage in the brain and its role in diseases involving brain inflammation or degeneration, such as Alzheimer’s disease and multiple sclerosis. The study was published in the peer-reviewed scientific journal Nature.

When I was in medical school, we were taught that the central nervous system (brain and spinal cord) did not have a typical lymphatic drainage system. Lymph is the immune fluid that circulates through the body, containing white blood cells to fight infection and destroy abnormal cells. This study aimed to look at the circulation of lymph in the mouse brain, but mice and humans do not have identical biology, so the findings may not be directly applicable. 

The study involved complex laboratory techniques, using a fluorescent antibody to assess the alignment of cells within the brain, examination for markers associated with a lymphatic drainage system and looking at the functional capacity of identified vessels to carry lymphatic fluid to and from the brain. 
Human samples taken from the brain at autopsy were used to investigate any structures found in mice.

The scientists found that the outer protective layers of the mouse brain showed cells that were clearly lined up, which suggested that these were vessels with a unique function. These cells showed the characteristic features of functional lymphatic vessels. These vessels appeared able to carry both fluid and immune cells from the fluid surrounding the brain and spinal cord (the cerebrospinal fluid), and were connected to the lymph nodes in the neck. The location of these vessels may have been the reason they have not been discovered before, thereby causing the belief that there is no lymphatic drainage system in the brain.

This may mean current thinking about how the brain works needs to be reassessed. The researchers go on to say it could be the malfunction of these vessels that could be the cause of a variety of brain disorders, such as multiple sclerosis and Alzheimer’s disease.

Summary: This mouse study has examined the circulation of lymph in the brain. It discovered previously unknown lymphatic vessels in the outer layers of the mouse brain. If accurate, the findings may call for a review of how the immune system in the brain functions, and shed new light on its role in brain diseases involving brain inflammation or degeneration. Though animal research can give a good insight into biological and disease processes, and how they may work in humans, the processes in humans and mice are not identical. Further studies are needed to confirm these findings and to assess whether this knowledge is transferable to humans. As such, it is too early to say whether the findings could one day have any implications for the treatment of degenerative brain conditions such as multiple sclerosis or Alzheimer’s.  

The original article in Nature can be found here.

Child Development and Brain Health

In teaching medical students about psychiatry, I say that there are two key factors that influence how an individual fares in life. One factor is biological vulnerability, and the other factor is developmental opportunity. A person may be born with a genetically influenced condition like dyslexia, or a genetic vulnerability to addiction (alcoholism, for example, tends to run in families). Someone with biological vulnerability may, however, do quite well if life is filled with developmental opportunity. A person who grows up in a stable family, who attends good schools, and who gets a good job has a life rich in developmental opportunities that may ultimately enable them to overcome the biological vulnerability.

Someone with dyslexia may attend schools that recognize the deficit and help the child learn to read well; or they may have the help of a skilled educational psychologist who can work the magic and overcome the learning differences. On the other hand, someone who grows up in less fortunate circumstances, like living in poverty or suffering a broken home, may do very well if they are biologically resilient and strong. Problems arise, however, when some suffers biological vulnerability as well as a life short on developmental opportunity. When we see the chronically mentally ill, we often see the overlap of these two conditions.

New research suggests that family income, and to a lesser degree parental education, are associated with brain structure differences in children and young adults. Focusing on brain regions critical for language, memory, and executive function in participants aged three to 20 years, scientists found that small differences in income were associated with relatively large differences in brain surface area in young people from the lowest-income families. This effect was smaller in higher-income families. Higher income was also associated with better performance in tests of cognitive ability. Increased levels of parental education were also related to increased brain surface area, although this effect was smaller when compared to the influence of income.

Although these study results do not suggest that low-income children have poor cognitive function, they indicate that interventions to reduce family poverty may help reduce socioeconomic disparities in child development and achievement.  The full text of the findings can be found here.

The Brain: A Good Introduction

One of my favorite journals, New Scientist, has an excellent introduction to the brain and how it works.

The brain is the most complex organ in the human body. It produces our every thought, action, memory, feeling and experience of the world. This jelly-like mass of tissue, weighing in at around 1.4 kilograms, contains a staggering one hundred billion nerve cells, or neurons.

The complexity of the connectivity between these cells is mind-boggling. Each neuron can make contact with thousands or even tens of thousands of others, via tiny structures called synapses. Our brains form a million new connections for every second of our lives. The pattern and strength of the connections is constantly changing and no two brains are alike.

It is in these changing connections that memories are stored, habits learned and personalities shaped, by reinforcing certain patterns of brain activity, and losing others. To read the article, click here.

Neuroscience of Belief

In the current issue of New Scientist I came across a good article on the neuroscience of belief. Graham Lawton writes, in part: Beliefs define how we see the world and act within it; without them, there would be no plots to behead soldiers, no war, no economic crises and no racism. There would also be no cathedrals, no nature reserves, no science and no art. Whatever beliefs you hold, it's hard to imagine life without them. Beliefs, more than anything else, are what make us human. They also come so naturally that we rarely stop to think how bizarre belief is.
In 1921, philosopher Bertrand Russell put it succinctly when he described belief as "the central problem in the analysis of mind". Believing, he said, is "the most 'mental' thing we do" – by which he meant the most removed from the "mere matter" that our brains are made of. How can a physical object like a human brain believe things? Philosophy has made little progress on Russell's central problem. But increasingly, scientists are stepping in.
The neuroscientific investigation of belief began in 2008, when Sam Harris (Harris, S., Sheth, S. A. and Cohen, M. S. (2008), Functional neuroimaging of belief, disbelief, and uncertainty. Ann Neurol., 63: 141–147) at the University of California, Los Angeles, put people into a brain scanner and asked them whether they believed in various written statements. Some were simple factual propositions, such as "California is larger than Rhode Island"; others were matters of personal belief, such as "There is probably no God". Harris found that statements people believed to be true produced little characteristic brain activity – just a few brief flickers in regions associated with reasoning and emotional reward. In contrast, disbelief produced longer and stronger activation in regions associated with deliberation and decision-making, as if the brain had to work harder to reach a state of disbelief. Statements the volunteers did not believe also activated regions associated with emotion, but in this case pain and disgust.

To read the full article, click here.