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BRAIN Initiative

An Indisposable Idea from a Disposable Diaper

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3D Silver Nanostructures
Caption: 3D silver nanostructures created using implosion fabrication. Credit: Daniel Oran, Massachusetts Institute of Technology

Using a screwdriver on the tiny microcircuits arrayed inside a computer hard drive can be a real eye strain. Even more challenging is building the microcircuits or other electronic components at the nanoscale, one-billionth of a meter or less.

That’s why researchers are always on the lookout for new tools to help them work on such a minute scale. But some of these incredibly tiny tools and scaffolds can derive from very unexpected sources.

As published in the journal Science, an NIH-funded team has developed a technique called implosion fabrication to build impressively small and intricate components on the nanoscale [1]. Its secret ingredient: water-swollen gels that you’d find in a baby’s disposable diaper.

A baby’s disposable diaper? If that sounds familiar, my blog highlighted a related technique called expansion microscopy a few years ago that uses water-swollen gels that are generated from a compound used in diapers called sodium polyacrylate.

The previously-reported microscopy technique, from the lab of Edward Boyden, Massachusetts Institute of Technology, Cambridge, embeds biological samples in a fine web of sodium polyacrylate. When water is added, the gel expands, blowing up the specimen to 100 times its original size. This groundbreaking technique, called expansion microscopy, has enabled labs around the world to use conventional microscopes for high-resolution, nanoscale imaging.

In the latest work, Boyden’s team, including co-first authors Daniel Oran and Samuel Rodriques, asked a simple question: What would happen if they applied the sample preparation technique used for expansion microscopy—only in reverse?

To find out, Boyden’s team created millimeter-sized blocks of the super-absorbent sodium polyacrylate diaper compound. After using a nifty trick for attaching molecular anchors in a 3D pattern, they dehydrated the gel and voila! The structures imploded and shrank down to one-thousandth their original size, while holding their 3D shape.

During the process, they can add to the anchors a range of functional molecules or elements. These include DNA, nanoparticles, semiconductors, or almost anything that’s needed.

While more work is needed to perfect the new technique, the researchers have already shown it can create objects one cubic millimeter in size, engineered to include intricate details down to about 50 nanometers. For comparison, a virus is about 30 to 50 nanometers.

These latest findings come as a reminder that advances in biomedicine often lead in wonderful and unexpected new directions. Out of the NIH-funded efforts related to The Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative, members of the Boyden Lab wanted to see the brain better using basic microscopes. Now, we have a widely-applicable promising new approach to nanofabrication.

Reference:

[1] 3D nanofabrication by volumetric deposition and controlled shrinkage of patterned scaffolds. Oran D, Rodriques SG, Gao R, Asano S, Skylar-Scott MA, Chen F, Tillberg PW, Marblestone AH, Boyden ES. Science. 2018 Dec 14;362(6420):1281-1285.

Links:

Size of the Nanoscale (Nano.gov)

Synthetic Neurobiology Group, Ed Boyden (MIT, Cambridge, MA)

The Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)

NIH Support: Common Fund; National Institute of Mental Health; National Institute of Biomedical Imaging and Bioengineering; National Human Genome Research Institute; National Institute on Drug Abuse; National Institute of Neurological Disorders and Stroke


Finding Beauty in the Nervous System of a Fruit Fly Larva

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Wow! Click on the video. If you’ve ever wondered where those pesky flies in your fruit bowl come from, you’re looking at it right now. It’s a fruit fly larva. And this 3D movie offers never-before-seen details into proprioception—the brain’s sixth sense of knowing the body’s location relative to nearby objects or, in this case, fruit.

This live-action video highlights the movement of the young fly’s proprioceptive nerve cells. They send signals to the fly brain that are essential for tracking the body’s position in space and coordinating movement. The colors indicate the depth of the nerve cells inside the body, showing those at the surface (orange) and those further within (blue).

Such movies make it possible, for the first time, to record precisely how every one of these sensory cells is arranged within the body. They also provide a unique window into how body positions are dynamically encoded in these cells, as a segmented larva inches along in search of food.

The video was created using a form of confocal microscopy called Swept Confocally Aligned Planar Excitation, or SCAPE. It captures 3D images by sweeping a sheet of laser light back and forth across a living sample. Even better, it does this while the microscope remains completely stationary—no need for a researcher to move any lenses up or down, or hold a live sample still.

Most impressively, with this new high-speed technology, developed with support from the NIH’s BRAIN Initiative, researchers are now able to capture videos like the one seen above in record time, with each whole volume recorded in under 1/10th of a second! That’s hundreds of times faster than with a conventional microscope, which scans objects point by point.

As reported in Current Biology, the team, led by Elizabeth Hillman and Wesley Grueber, Columbia University, New York, didn’t stop at characterizing the structural details and physical movements of nerve cells involved in proprioception in a crawling larva. In another set of imaging experiments, they went a step further, capturing faint flashes of green in individual labeled nerve cells each time they fired. (You have to look very closely to see them.) With each wave of motion, proprioceptive nerve cells light up in sequence, demonstrating precisely when they are sending signals to the animal’s brain.

From such videos, the researchers have generated a huge amount of data on the position and activity of each proprioceptive nerve cell. The data show that the specific position of each cell makes it uniquely sensitive to changes in position of particular segments of a larva’s body. While most of the proprioceptive nerve cells fired when their respective body segment contracted, others were attuned to fire when a larval segment stretched.

Taken together, the data show that proprioceptive nerve cells provide the brain with a detailed sequence of signals, reflecting each part of a young fly’s undulating body. It’s clear that every proprioceptive neuron has a unique role to play in the process. The researchers now will create similar movies capturing neurons in the fly’s central nervous system.

A holy grail of the BRAIN Initiative is to capture the brain in action. With these advances in imaging larval flies, researchers are getting ever closer to understanding the coordinated activities of an organism’s complete nervous system—though this one is a lot simpler than ours! And perhaps this movie—and the anticipation of the sequels to come—may even inspire a newfound appreciation for those pesky flies that sometimes hover nearby.

Reference:

[1] Characterization of Proprioceptive System Dynamics in Behaving Drosophila Larvae Using High-Speed Volumetric Microscopy. Vaadia RD, Li W, Voleti V, Singhania A, Hillman EMC, Grueber WB. Curr Biol. 2019 Mar 18;29(6):935-944.e4.

Links:

Using Research Organisms to Study Health and Disease (National Institute of General Medical Sciences/NIH)

The Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)

Hillman Lab (Columbia University, New York)

Grueber Lab (Columbia University, New York)

NIH Support: National Institute of Neurological Disorders and Stroke; Eunice Kennedy Shriver National Institute of Child Health and Human Development


Taking Brain Imaging Even Deeper

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Thanks to yet another amazing advance made possible by the NIH-led Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative, I can now take you on a 3D fly-through of all six layers of the part of the mammalian brain that processes external signals into vision. This unprecedented view is made possible by three-photon microscopy, a low-energy imaging approach that is allowing researchers to peer deeply within the brains of living creatures without damaging or killing their brain cells.

The basic idea of multi-photon microscopy is this: for fluorescence microscopy to work, you want to deliver a specific energy level of photons (usually with a laser) to excite a fluorescent molecule, so that it will emit light at a slightly lower energy (longer wavelength) and be visualized as a burst of colored light in the microscope. That’s how fluorescence works. Green fluorescent protein (GFP) is one of many proteins that can be engineered into cells or mice to make that possible.

But for that version of the approach to work on tissue, the excited photons need to penetrate deeply, and that’s not possible for such high energy photons. So two-photon strategies were developed, where it takes the sum of the energy of two simultaneous photons to hit the target in order to activate the fluorophore.

That approach has made a big difference, but for deep tissue penetration the photons are still too high in energy. Enter the three-photon version! Now the even lower energy of the photons makes tissue more optically transparent, though for activation of the fluorescent protein, three photons have to hit it simultaneously. But that’s part of the beauty of the system—the visual “noise” also goes down.

This particular video shows what takes place in the visual cortex of mice when objects pass before their eyes. As the objects appear, specific neurons (green) are activated to process the incoming information. Nearby, and slightly obscuring the view, are the blood vessels (pink, violet) that nourish the brain. At 33 seconds into the video, you can see the neurons’ myelin sheaths (pink) branching into the white matter of the brain’s subplate, which plays a key role in organizing the visual cortex during development.

This video comes from a recent paper in Nature Communications by a team from Massachusetts Institute of Technology, Cambridge [1]. To obtain this pioneering view of the brain, Mriganka Sur, Murat Yildirim, and their colleagues built an innovative microscope that emits three low-energy photons. After carefully optimizing the system, they were able to peer more than 1,000 microns (0.05 inches) deep into the visual cortex of a live, alert mouse, far surpassing the imaging capacity of standard one-photon microscopy (100 microns) and two-photon microscopy (400-500 microns).

This improved imaging depth allowed the team to plumb all six layers of the visual cortex (two-photon microscopy tops out at about three layers), as well as to record in real time the brain’s visual processing activities. Helping the researchers to achieve this feat was the availability of a genetically engineered mouse model in which the cells of the visual cortex are color labelled to distinguish blood vessels from neurons, and to show when neurons are active.

During their in-depth imaging experiments, the MIT researchers found that each of the visual cortex’s six layers exhibited different responses to incoming visual information. One of the team’s most fascinating discoveries is that neurons residing on the subplate are actually quite active in adult animals. It had been assumed that these subplate neurons were active only during development. Their role in mature animals is now an open question for further study.

Sur often likens the work in his neuroscience lab to astronomers and their perpetual quest to see further into the cosmos—but his goal is to see ever deeper into the brain. His group, along with many other researchers supported by the BRAIN Initiative, are indeed proving themselves to be biological explorers of the first order.

Reference:

[1] Functional imaging of visual cortical layers and subplate in awake mice with optimized three-photon microscopy. Yildirim M, Sugihara H, So PTC, Sur M. Nat Commun. 2019 Jan 11;10(1):177.

Links:

Sur Lab (Massachusetts Institute of Technology, Cambridge)

The Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)

NIH Support: National Eye Institute; National Institute of Neurological Disorders and Stroke; National Institute of Biomedical Imaging and Bioengineering


Discovering a Source of Laughter in the Brain

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cingulum bundle
Illustration showing how an electrode was inserted into the cingulum bundle. Courtesy of American Society for Clinical Investigation

If laughter really is the best medicine, wouldn’t it be great if we could learn more about what goes on in the brain when we laugh? Neuroscientists recently made some major progress on this front by pinpointing a part of the brain that, when stimulated, never fails to induce smiles and laughter.

In their study conducted in three patients undergoing electrical stimulation brain mapping as part of epilepsy treatment, the NIH-funded team found that stimulation of a specific tract of neural fibers, called the cingulum bundle, triggered laughter, smiles, and a sense of calm. Not only do the findings shed new light on the biology of laughter, researchers hope they may also lead to new strategies for treating a range of conditions, including anxiety, depression, and chronic pain.

In people with epilepsy whose seizures are poorly controlled with medication, surgery to remove seizure-inducing brain tissue sometimes helps. People awaiting such surgeries must first undergo a procedure known as intracranial electroencephalography (iEEG). This involves temporarily placing 10 to 20 arrays of tiny electrodes in the brain for up to several weeks, in order to pinpoint the source of a patient’s seizures in the brain. With the patient’s permission, those electrodes can also enable physician-researchers to stimulate various regions of the patient’s brain to map their functions and make potentially new and unexpected discoveries.

In the new study, published in The Journal of Clinical Investigation, Jon T. Willie, Kelly Bijanki, and their colleagues at Emory University School of Medicine, Atlanta, looked at a 23-year-old undergoing iEEG for 8 weeks in preparation for surgery to treat her uncontrolled epilepsy [1]. One of the electrodes implanted in her brain was located within the cingulum bundle and, when that area was stimulated for research purposes, the woman experienced an uncontrollable urge to laugh. Not only was the woman given to smiles and giggles, she also reported feeling relaxed and calm.

As a further and more objective test of her mood, the researchers asked the woman to interpret the expression of faces on a computer screen as happy, sad, or neutral. Electrical stimulation to the cingulum bundle led her to see those faces as happier, a sign of a generally more positive mood. A full evaluation of her mental state also showed she was fully aware and alert.

To confirm the findings, the researchers looked to two other patients, a 40-year-old man and a 28-year-old woman, both undergoing iEEG in the course of epilepsy treatment. In those two volunteers, stimulation of the cingulum bundle also triggered laughter and reduced anxiety with otherwise normal cognition.

Willie notes that the cingulum bundle links many brain areas together. He likens it to a super highway with lots of on and off ramps. He suspects the spot they’ve uncovered lies at a key intersection, providing access to various brain networks regulating mood, emotion, and social interaction.

Previous research has shown that stimulation of other parts of the brain can also prompt patients to laugh. However, what makes stimulation of the cingulum bundle a particularly promising approach is that it not only triggers laughter, but also reduces anxiety.

The new findings suggest that stimulation of the cingulum bundle may be useful for calming patients’ anxieties during neurosurgeries in which they must remain awake. In fact, Willie’s team did so during their 23-year-old woman’s subsequent epilepsy surgery. Each time she became distressed, the stimulation provided immediate relief. Also, if traditional deep brain stimulation or less invasive means of brain stimulation can be developed and found to be safe for long-term use, they may offer new ways to treat depression, anxiety disorders, and/or chronic pain.

Meanwhile, Willie’s team is hard at work using similar approaches to map brain areas involved in other aspects of mood, including fear, sadness, and anxiety. Together with the multidisciplinary work being mounted by the NIH-led BRAIN Initiative, these kinds of studies promise to reveal functionalities of the human brain that have previously been out of reach, with profound consequences for neuroscience and human medicine.

Reference:

[1] Cingulum stimulation enhances positive affect and anxiolysis to facilitate awake craniotomy. Bijanki KR, Manns JR, Inman CS, Choi KS, Harati S, Pedersen NP, Drane DL, Waters AC, Fasano RE, Mayberg HS, Willie JT. J Clin Invest. 2018 Dec 27.

Links:

Video: Patient’s Response (Bijanki et al. The Journal of Clinical Investigation)

Epilepsy Information Page (National Institute of Neurological Disease and Stroke/NIH)

Jon T. Willie (Emory University, Atlanta, GA)

NIH Support: National Institute of Neurological Disease and Stroke; National Center for Advancing Translational Sciences


‘Tis the Season for Good Cheer

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Whether it’s Rockefeller Center, the White House, or somewhere else across the land, ‘tis the season to gather with neighbors for a communal holiday tree-lighting ceremony. But this festive image has more do with those cups of cider in everyone’s hands than admiring the perfect Douglas fir. What looks like lights and branches are actually components of a high-resolution map from a part of the brain that controls thirst.

The map, drawn up from mouse studies, shows that when thirst arises, neurons activate a gene called c-fos (red)—lighting up the tree—indicating it’s time for a drink. In response, other neurons (green) direct additional parts of the brain to compensate by managing internal water levels. In a mouse that’s no longer thirsty, the tree would look almost all green.

This wiring map comes from a part of the brain called the hypothalamus, which is best known for its role in hunger, thirst, and energy balance. Thanks to powerful molecular tools from NIH’s Brain Research through Advancing Innovative Technologies (BRAIN) Initiative, Yuki Oka of the California Institute of Technology, Pasadena, and his team were able to draw detailed maps of the tree-shaped region, called the median preoptic nucleus (MnPO).

Using a technique called optogenetics, Oka’s team, led by Vineet Augustine, could selectively turn on genes in the MnPO [1]. By doing so, they could control a mouse’s thirst and trace the precise control pathways responsible for drinking or not.

This holiday season, as you gather with loved ones, take a moment to savor the beautiful complexity of biology and the gift of human health. Happy holidays to all of you, and peace and joy into the new year!

Reference:

[1] Hierarchical neural architecture underlying thirst regulation. Augustine V, Gokce SK, Lee S, Wang B, Davidson TJ, Reimann F, Gribble F, Deisseroth K, Lois C, Oka Y. Nature. 2018 Mar 8;555(7695):204-209. 

Links:

Oka Lab, California Institute of Technology, Pasadena

The BRAIN Initiative (NIH)

NIH Support: National Institute of Neurological Disorders and Stroke


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