Considering all the recent advances in mapping the complex circuitry of the human brain, you’d think we’d know all there is to know about the brain’s basic anatomy. That’s what makes the finding that I’m about to share with you so remarkable. Contrary to what I learned in medical school, the body’s lymphatic system extends to the brain—a discovery that could revolutionize our understanding of many brain disorders, from Alzheimer’s disease to multiple sclerosis (MS).
Researchers from the National Institute of Neurological Disorders and Stroke (NINDS), the National Cancer Institute (NCI), and the University of Virginia, Charlottesville made this discovery by using a special MRI technique to scan the brains of healthy human volunteers . As you see in this 3D video created from scans of a 47-year-old woman, the brain—just like the neck, chest, limbs, and other parts of the body—possesses a network of lymphatic vessels (green) that serves as a highway to circulate key immune cells and return metabolic waste products to the bloodstream.
As a graduate student in the 1980s, Bruce Yankner wondered what if cancer-causing genes switched on in non-dividing neurons of the brain. Rather than form a tumor, would those genes cause neurons to degenerate? To explore such what-ifs, Yankner spent his days tinkering with neural cells, using viruses to insert various mutant genes and study their effects. In a stroke of luck, one of Yankner’s insertions encoded a precursor to a protein called amyloid. Those experiments and later ones from Yankner’s own lab showed definitively that high concentrations of amyloid, as found in the brains of people with Alzheimer’s disease, are toxic to neural cells .
The discovery set Yankner on a career path to study normal changes in the aging human brain and their connection to neurodegenerative diseases. At Harvard Medical School, Boston, Yankner and his colleague George Church are now recipients of an NIH Director’s 2016 Transformative Research Award to apply what they’ve learned about the aging brain to study changes in the brains of younger people with schizophrenia and bipolar disorder, two poorly understood psychiatric disorders.
Credit: Raunak Basu, University of Utah, Salt Lake City
The final frontier? Trekkies would probably say it’s space, but mapping the brain—the most complicated biological structure in the known universe—is turning out to be an amazing adventure in its own right. Not only are researchers getting better at charting the brain’s densely packed and varied cellular topography, they are starting to identify the molecules that neurons use to connect into the distinct information-processing circuits that allow all walks of life to think and experience the world.
This image shows distinct neural connections in a cross section of a mouse’s hippocampus, a region of the brain involved in the memory of facts and events. The large, crescent-shaped area in green is hippocampal zone CA1. Its highly specialized neurons, called place cells, serve as the brain’s GPS system to track location. It appears green because these neurons express cadherin-10. This protein serves as a kind of molecular glue that likely imparts specific functional properties to this region. 
I had asthma as a child, and I still occasionally develop mild wheezing from exercising in cold air or catching a bad cold. I keep an inhaler on hand for those occasions, as this is a quick and effective way to deliver a medication that opens up those constricted airways. Now, an NIH-supported team has made the surprising discovery that some asthma medicines may also hold the potential to treat or help prevent Parkinson’s disease, a chronic, progressive movement disorder that affects at least a half-million Americans.
The results, published recently in the journal Science, provide yet another example of the tremendous potential of testing drugs originally intended for treating one disease for possible use in others . In this particular instance, researchers screened a library of more than 1,100 well-characterized chemical compounds—including drugs approved by the Food and Drug Administration for treating asthma—to see if they showed any activity against a molecular mechanism known to be involved in Parkinson’s disease.
Caption: Neuronal circuits in the mouse retina. Cone photoreceptors (red) enable color vision; bipolar neurons (magenta) relay information further along the circuit; and a subtype of bipolar neuron (green) helps process signals sensed by other photoreceptors in dim light. Credit: Brian Liu and Melanie Samuel, Baylor College of Medicine, Houston.
When most people think of reprogramming something, they probably think of writing code for a computer or typing commands into their smartphone. Melanie Samuel thinks of brain circuits, the networks of interconnected neurons that allow different parts of the brain to work together in processing information.
Samuel, a researcher at Baylor College of Medicine, Houston, wants to learn to reprogram the connections, or synapses, of brain circuits that function less well in aging and disease and limit our memory and ability to learn. She has received a 2016 NIH Director’s New Innovator Award to decipher the molecular cues that encourage the repair of damaged synapses or enable neurons to form new connections with other neurons. Because extensive synapse loss is central to most degenerative brain diseases, Samuel’s reprogramming efforts could help point the way to preventing or correcting wiring defects before they advance to serious and potentially irreversible cognitive problems.