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It all started with 80 bulbs strung on a New York City tree

Decorative light bulbs, like this 1925 two-faced doll's head, became popular as electrification spread in the early 20th century.

In much of the world, December is a month of twinkling lights. Whether for religious or secular celebrations, the variety and functionality of lights have exploded in recent years, abetted by cheap and colorful LEDs and compact electronics. Homeowners can illuminate the eaves with iridescent icicles, shroud their shrubs with twinkling mesh nets, or mount massive menorahs on their minivans.

But decorative lights aren't new. On 22 December 1882, Edward H. Johnson, vice president of the Edison Electric Light Co., debuted electric Christmas lights when he lit up 80 hand-wired bulbs on a tree in the parlor of his New York City home. Johnson opted for red, white, and blue bulbs, and he mounted the tree on a revolving box. As the tree turned, the lights blinked on and off, creating a "continuous twinkling of dancing colors," as William Croffut reported in the Detroit Post and Tribune. (Croffut's account and many other wonderful facts about the history of decorative lights are available on the website Old Christmas Tree Lights.)

Two years later, Johnson's growing display caught the attention of the New York Times. His tree now boasted 120 lights and more colors. He also created a fire "burning" in the fireplace; in reality, it was colored paper illuminated from below by electric lights.

Johnson was part early adopter, part showman, and part publicist for the possibilities of electricity. But electric Christmas lights were not exactly practical at the time because most homes were not yet wired for electricity. Lighting had to be hand wired, and there was no standardization in bulbs or sockets. For the next several decades, decorative lights remained the playthings of the wealthy elite.

In 1903, GE rocked the home-decorating world by introducing the first strings of prewired light sockets.

Meanwhile, manufacturers continued to market new products. In 1890, the Edison Lamp Co. began advertising miniature incandescent lamps that could be interwoven into garlands or used for decorating Christmas trees. A 1900 advertisement from General Electric (formed through the 1892 merger of Edison General Electric and Thomson-Houston Electric) touted the advantages of electric Christmas lighting over gas and candles: "No Danger, Smoke or Smell." Customers not quite willing to commit to the lights could rent them for the season.

In 1903, GE rocked the home-decorating world by introducing the first strings of prewired light sockets. The GE lights came in strands, or festoons, of 8, 16, 24, or 32 bulbs. Additional 8-bulb festoons could be added as desired. The sets included 50 feet (15 meters) of flexible cord and screwed into a lamp socket. The lights were connected in series, so if a bulb burned out, the rest of the line went dark. Detailed instructions described how to troubleshoot problems if the lights did not shine. A 24-light set cost US $12 (about $325 today) and could illuminate a medium table-top tree.

The GE lights were still out of reach for the average consumer, but prices quickly dropped as competitors entered the market. Just four years later, Excelsior Supply Co. of Chicago advertised "Winking Fairy Lights for Christmas Trees" in Hardware Dealers' Magazine. Each 8-bulb set cost only $5, with a wholesale price of $3.50.

U.S. President Grover Cleveland was an early adopter of the electrified Christmas tree, as shown in this 1896 photo. White House Historical Association

The earliest Christmas lights used miniature versions of Edison's pear-shaped carbon-filament bulbs, which had fragile exhaust tips that were prone to breaking. In 1910 GE changed its basic design to a round bulb, although still with the exhaust tip. In 1916, GE introduced tungsten filaments and gave the new design the Mazda trademark. Two years later, they removed the tips, making the bulbs more fully round. In 1919 GE changed its bulb shape again, this time to the familiar cone resembling a candle flame. This bulb shape remained in use until the late 1970s and more recently has resurfaced as a "vintage" style. (Anyone interested in dating old sets of lights can consult the Old Christmas Tree Lights website, which was originally created by the brothers Bill and George Nelson.)

Just as the "typical" bulb was evolving, more decorative figural bulbs were arriving on the scene. By 1908, the Sears and Roebuck catalog featured a set of a dozen painted glass bulbs shaped like small fruits and nuts for $2.75. In 1910, an article in Scientific American described Christmas bulbs in the shape of flowers, animals, snowmen, angels, and Santa Claus. The 1919 Decorative Lamps catalog of the American Ever Ready Co. (precursor to the Eveready Battery Co.) branched out to bulbs of St. Patrick, Halloween pumpkins, clowns, and policemen. Austria, Germany, and Japan became famous for exporting figural bulbs.

These novelty bulbs had their challenges. Depending on the orientation of the base, some figures hung perpetually upside down. The paint could easily flake or wear off. Some of the designs are just creepy—like the two-faced doll's head shown at top. But I would happily decorate my home with many of these antique bulbs. To me, they're warmer and more inviting than some of the brash lights of today.

While researching this month's column, I stumbled upon the doll's head bulb while scrolling through the online collections of the Smithsonian Institution. I had hoped to uncover more information about the object, but the online records had limited details. I did, however, learn a few things about the donor.

The lightbulb came to the Smithsonian Institution's National Museum of American History in 1974 through a bequest from Edith R. Meggers, who had died the previous year. Altogether, Meggers donated more than 800 objects , including badges and pins, dollhouse furniture, toys and games, calculators, typewriters, and electrical insulators. Meggers shared a passion for travel and collecting with her husband, William. They displayed their treasures in their home, which they dubbed "The Meggers Museum of Technology." Their collecting habits were well known in the Washington, D.C., area, and the Washington Post ran a feature article on them in 1941 with the subheading "They Collect Just About Anything You Can Name."

Edith Meggers donated more than 800 objects , including badges and pins, dollhouse furniture, toys and games, calculators, typewriters, and electrical insulators.

Collecting was just a hobby, though. Edith Meggers worked in the Building Technology Division of the National Bureau of Standards (NBS), which is where she met her husband; they married in 1920. Although Edith's name might not be familiar to Spectrum readers, her husband's may be. William F. Meggers was the chief of the Spectroscopy Section at NBS.

When William Meggers first came to NBS, spectroscopy was still a developing technique, and so he spent the first few years studying the process. His early papers examined the influence of the physical condition of samples, the method of excitation, and the apparatus used to obtain and record the spectral data. In 1922, Meggers published an influential paper (along with C.C. Kiess and F.J. Stimpson) on the use of spectrography in chemical analysis. Over his long career, he studied the spectra of 50 elements, establishing international standards for measurement.

This 1895 ad equates electric lights with wealth and conviviality. History of Advertising Trust/Heritage Images/Getty Images

Of course, being a famous physicist and an avid collector doesn't fully explain how the Meggers' Christmas lights and other objects found their way to the Smithsonian. The bequest of Edith Meggers was handled by her attorney and involved a dozen different curators because the collection spanned several divisions. Unfortunately, the donation records are sealed to researchers until 2032. But it is possible that Edith and Bill's collecting habits wore off on their daughter, Betty Jane Meggers. She earned her Ph.D. in archaeology from Columbia University in 1952 with a dissertation focusing on Marajó Island, Brazil. She enjoyed a long career with the Smithsonian Institution, where she was the director of the Latin American Archaeology Program at the National Museum of Natural History at the time of her death in 2012. So Betty Jane would have known the process for donating objects of value.

As a former curator with the Smithsonian, I remember getting phone calls and emails from potential donors who were cleaning out basements and attics and wondered if their mementos were worthy of inclusion in a national museum collection. Often, curators have to say no due to space limitations. However, if the object's provenance is well documented and the item is in good condition, curators may ask for more information, especially if there is a good story attached to it.

I found it fascinating to go down the rabbit hole of the history of the electrification of Christmas.

The story is key because curators will have to justify the acquisition, explaining how the object will fit into the museum's collection plan and how it will be used in exhibits, educational programming, or research projects. Having additional contextual materials, such as photos or user manuals, helps make the case for the object's worthiness.

Another tip for donating is to make sure you match the item to the proper museum, library, or archive. A national museum might not be the right fit (and even if it's accepted, your item is much more likely to be put into storage and never go on display). Consider regional and local museums as well as specialized institutions. For example, after my father died, I sent a photo of some of his engineering books to Jason Dean, vice president for special collections at the Linda Hall Library, in Kansas City, Mo. The Linda Hall is an independent research library that specializes in science, technology, and engineering. Dean took some of the books, and I had to pay shipping, but I am happy that they found a new home.

I'm one of those people who love learning through objects, and I enjoy trying to figure out what stories these old, everyday items can tell. Although I wish I could have learned more about the figurine light that Edith Meggers gifted the National Museum of American History, I found it fascinating to go down the rabbit hole of the history of the electrification of Christmas and to learn more about Edith and her family. Perhaps someday something of mine will end up in a museum—but my curatorial opinion is that the story isn't there yet.

Part of a continuing serieslooking at photographs of historical artifacts that embrace the boundless potential of technology.

An abridged version of this article appears in the December 2021 print issue as "It's a Wonderful Light."

Allison Marsh is a professor at the University of South Carolina and codirector of the university's Ann Johnson Institute for Science, Technology & Society. She combines her interests in engineering, history, and museum objects to write the Past Forward column, which tells the story of technology through historical artifacts.

Exponential growth comes to neural implants

Imagine a portable computer built from a network of 86 billion switches, capable of general intelligence sophisticated enough to build a spacefaring civilization—but weighing just 1.2 to 1.3 kilograms, consuming just 20 watts of power, and jiggling like Jell-O as it moves. There’s one inside your skull right now. It is a breathtaking achievement of biological evolution. But there are no blueprints.

Now imagine trying to figure out how this wonder of bioelectronics works without a way to observe its microcircuitry in action. That’s like asking a microelectronics engineer to reverse engineer the architecture, microcode, and operating system running on a state-of-the-art processor without the use of a digital logic probe, which would be a virtually impossible task.

So it’s easy to understand why many of the operational details of humans’ brains (and even the brains of mice and much simpler organisms) remain so mysterious, even to neuroscientists. People often think of technology as applied science, but the scientific study of brains is essentially applied sensor technology. Each invention of a new way to measure brain activity—including scalp electrodes, MRIs, and microchips pressed into the surface of the cortex—has unlocked major advances in our understanding of the most complex, and most human, of all our organs.

The brain is essentially an electrical organ, and that fact plus its gelatinous consistency pose a hard technological problem. In 2010, I met with leading neuroscientists at the Howard Hughes Medical Institute (HHMI) to explore how we might use advanced microelectronics to invent a new sensor. Our goal: to listen in on the electrical conversations taking place among thousands of neurons at once in any given thimbleful of brain tissue.

Timothy D. Harris, a senior scientist at HHMI, told me that “we need to record every spike from every neuron” in a localized neural circuit within a freely moving animal. That would mean building a digital probe long enough to reach any part of the thinking organ, but slim enough not to destroy fragile tissues on its way in. The probe would need to be durable enough to stay put and record reliably for weeks or even months as the brain guides the body through complex behaviors.

Different kinds of neural probes pick up activity from firing neurons: three tines of a Utah array with one electrode on each tine [left], a single slender tungsten wire electrode [center], and a Neuropixels shank that has electrodes all along its length [checkered pattern, right].Massachusetts General Hospital/Imec/Nature Neuroscience

For an electrical engineer, those requirements add up to a very tall order. But more than a decade of R&D by a global, multidisciplinary team of engineers, neuroscientists, and software designers has at last met the challenge, producing a remarkable new tool that is now being put to use in hundreds of labs around the globe.

As chief scientist at Imec, a leading independent nanoelectronics R&D institute, in Belgium, I saw the opportunity to extend advanced semiconductor technology to serve broad new swaths of biomedicine and brain science. Envisioning and shepherding the technological aspects of this ambitious project has been one of the highlights of my career.

We named the system Neuropixels because it functions like an imaging device, but one that records electrical rather than photonic fields. Early experiments already underway—including some in humans—have helped explore age-old questions about the brain. How do physiological needs produce motivational drives, such as thirst and hunger? What regulates behaviors essential to survival? How does our neural system map the position of an individual within a physical environment?

Successes in these preliminary studies give us confidence that Neuropixels is shifting neuroscience into a higher gear that will deliver faster insights into a wide range of normal behaviors and potentially enable better treatments for brain disorders such as epilepsy and Parkinson’s disease.

Version 2.0 of the system, demonstrated last year, increases the sensor count by about an order of magnitude over that of the initial version produced just four years earlier. It paves the way for future brain-computer interfaces that may enable paralyzed people to communicate at speeds approaching those of normal conversation. With version 3.0 already in early development, we believe that Neuropixels is just at the beginning of a long road of exponential Moore’s Law–like growth in capabilities.

In the 1950s, researchers used a primitive electronic sensor to identify the misfiring neurons that give rise to Parkinson’s disease. During the 70 years since, the technology has come far, as the microelectronics revolution miniaturized all the components that go into a brain probe: from the electrodes that pick up the tiny voltage spikes that neurons emit when they fire, to the amplifiers and digitizers that boost signals and reduce noise, to the thin wires that transmit power into the probe and carry data out.

By the time I started working with HHMI neuroscientists in 2010, the best electrophysiology probes, made by NeuroNexus and Blackrock Neurotech, could record the activity of roughly 100 neurons at a time. But they were able to monitor only cells in the cortical areas near the brain’s surface. The shallow sensors were thus unable to access deep brain regions—such as the hypothalamus, thalamus, basal ganglia, and limbic system—that govern hunger, thirst, sleep, pain, memory, emotions, and other important perceptions and behaviors. Companies such as Plexon make probes that reach deeper into the brain, but they are limited to sampling 10 to 15 neurons simultaneously. We set for ourselves a bold goal of improving on that number by one or two orders of magnitude.

We needed a way to place thousands of micrometer-size electrodes directly in contact with vertical columns of neurons, anywhere in the brain.

To understand how brain circuits work, we really need to record the individual, rapid-fire activity of hundreds of neurons as they exchange information in a living animal. External electrodes on the skull don’t have enough spatial resolution, and functional MRI technology lacks the speed necessary to record fast-changing signals. Eavesdropping on these conversations requires being in the room where it happens: We needed a way to place thousands of micrometer-size electrodes directly in contact with vertical columns of neurons, anywhere in the brain. (Fortuitously, neuroscientists have discovered that when a brain region is active, correlated signals pass through the region both vertically and horizontally.)

These functional goals drove our design toward long, slender silicon shanks packed with electrical sensors. We soon realized, however, that we faced a major materials issue. We would need to use Imec’s CMOS fab to mass-produce complex devices by the thousands to make them affordable to research labs. But CMOS-compatible electronics are rigid when packed at high density.

The team realized that they could mount two Neuropixels 2.0 probes on one headstage, the board that sits outside the skull, providing a total of eight shanks with 10,240 recording electrodes.Imec

The brain, in contrast, has the same elasticity as Greek yogurt. Try inserting strands of angel-hair pasta into yogurt and then shaking them a few times, and you’ll see the problem. If the pasta is too wet, it will bend as it goes in or won’t go in at all. Too dry, and it breaks. How would we build shanks that could stay straight going in yet flex enough inside a jiggling brain to remain intact for months without damaging adjacent brain cells?

Experts in brain biology suggested that we use gold or platinum for the electrodes and an organometallic polymer for the shanks. But none of those are compatible with advanced CMOS fabrication. After some research and lots of engineering, my Imec colleague Silke Musa invented a form of titanium nitride—an extremely tough electroceramic—that is compatible with both CMOS fabs and animal brains. The material is also porous, which gives it a low impedance; that quality is very helpful in getting currents in and clean signals out without heating the nearby cells, creating noise, and spoiling the data.

Thanks to an enormous amount of materials-science research and some techniques borrowed from microelectromechanical systems (MEMS), we are now able to control the internal stresses created during the deposition and etching of the silicon shanks and the titanium nitride electrodes so that the shanks consistently come out almost perfectly straight, despite being only 23 micrometers (µm) thick. Each probe consists of four parallel shanks, and each shank is studded with 1,280 electrodes. At 1 centimeter in length, the probes are long enough to reach any spot in a mouse’s brain. Mouse studies published in 2021 showed that Neuropixels 2.0 devices can collect data from the same neurons continuously for over six months as the rodents go about their lives.

The thousandfold difference in elasticity between CMOS-compatible shanks and brain tissue presented us with another major problem during such long-term studies: how to keep track of individual neurons as the probes inevitably shift in position relative to the moving brain. Neurons are 20 to 100 µm in size; each square pixel (as we call the electrodes) is 15 µm across, small enough so that it can record the isolated activity of a single neuron. But over six months of jostling activity, the probe as a whole can move within the brain by up to 500 µm. Any particular pixel might see several neurons come and go during that time.

The most common neural recording device today is the Utah array [top image, at left], which has one electrode at the tip of each of its tines. In contrast, a Neuropixels probe [top image, at right] has hundreds of electrodes along each of its long shanks. An image taken by a scanning electron microscope [bottom] magnifies the tips of several Neuropixels shanks.Massachusetts General Hospital/Imec/Nature Neuroscience

The 1,280 electrodes on each shank are individually addressable, and the four parallel shanks give us an effectively 2D readout, which is quite analogous to a CMOS camera image, and the inspiration for the name Neuropixels. That similarity made me realize that this problem of neurons shifting relative to pixels is directly analogous to image stabilization. Just like the subject filmed by a shaky camera, neurons in a chunk of brain are correlated in their electrical behavior. We were able to adapt knowledge and algorithms developed years ago for fixing camera shake to solve our problem of probe shake. With the stabilization software active, we are now able to apply automatic corrections when neural circuits move across any or all of the four shanks.

Version 2.0 shrank the headstage—the board that sits outside the skull, controls the implanted probes, and outputs digital data—to the size of a thumbnail. A single headstage and base can now support two probes, each extending four shanks, for a total of 10,240 recording electrodes. Control software and apps written by a fast-growing user base of Neuropixels researchers allow real-time, 30-kilohertz sampling of the firing activity of 768 distinct neurons at once, selected at will from the thousands of neurons touched by the probes. That high sampling rate, which is 500 times as fast as the 60 frames per second typically recorded by CMOS imaging chips, produces a flood of data, but the devices cannot yet capture activity from every neuron contacted. Continued advances in computing will help us ease those bandwidth limitations in future generations of the technology.

In just fouryears, we have nearly doubled the pixel density, doubled the number of pixels we can record from simultaneously, and increased the overall pixel count more than tenfold, while shrinking the size of the external electronics by half. That Moore’s Law–like pace of progress has been driven in large part by the use of commercial-scale CMOS and MEMS fabrication processes, and we see it continuing.

A next-gen design, Neuropixels 3.0, is already under development and on track for release around 2025, maintaining a four-year cadence. In 3.0, we expect the pixel count to leap again, to allow eavesdropping on perhaps 50,000 to 100,000 neurons. We are also aiming to add probes and to triple or quadruple the output bandwidth, while slimming the base by another factor of two.

That Moore’s Law–like pace of progress has been driven in large part by the use of commercial-scale CMOS fabrication processes.

Just as was true of microchips in the early days of the semiconductor industry, it’s hard to predict all the applications Neuropixels technology will find. Adoption has skyrocketed since 2017. Researchers at more than 650 labs around the world now use Neuropixels devices, and a thriving open-source community has appeared to create apps for them. It has been fascinating to see the projects that have sprung up: For example, the Allen Institute for Brain Science in Seattle recently used Neuropixels to create a database of activity from 100,000-odd neurons involved in visual perception, while a group at Stanford University used the devices to map how the sensation of thirst manifests across 34 different parts of the mouse brain.

We have begun fabricating longer probes of up to 5 cm and have defined a path to probes of 15 cm—big enough to reach the center of a human brain. The first trials of Neuropixels in humans were a success, and soon we expect the devices will be used to better position the implanted stimulators that quiet the tremors caused by Parkinson’s disease, with 10-µm accuracy. Soon, the devices may also help identify which regions are causing seizures in the brains of people with epilepsy, so that corrective surgery eliminates the problematic bits and no more.

The first Neuropixels device [top] had one shank with 966 electrodes. Neuropixels 2.0 [bottom] has four shanks with 1,280 electrodes each. Two probes can be mounted on one headstage.Imec

Future generations of the technology could play a key role as sensors that enable people who become “locked in” by neurodegenerative diseases or traumatic injury to communicate at speeds approaching those of typical conversation. Every year, some 64,000 people worldwide develop motor neuron disease, one of the more common causes of such entrapment. Though a great deal more work lies ahead to realize the potential of Neuropixels for this critical application, we believe that fast and practical brain-based communication will require precise monitoring of the activity of large numbers of neurons for long periods of time.

An electrical, analog-to-digital interface from wetware to hardware has been a long time coming. But thanks to a happy confluence of advances in neuroscience and microelectronics engineering, we finally have a tool that will let us begin to reverse engineer the wonders of the brain.

This article appears in the June 2022 print issue as “Eavesdropping on the Brain.”

Author Barun Dutta [above] of Imec brought his semiconductor expertise to the field of neuroscience.Fred Loosen/Imec

An unusual union of big tech and big science created Neuropixels, a fundamentally new technology for observing brains in action. The alliance also created a shared global facility for collaborative neuroscience akin to the CERN particle accelerator for high-energy physics.

The partnership began with conversations between Barun Dutta and Timothy D. Harris in 2010. Dutta is chief scientist of Imec, a leading nonprofit nanoelectronics R&D institute in Belgium, and had use of state-of-the-art semiconductor manufacturing facilities. Harris, who directs the applied physics and instrumentation group at the Howard Hughes Medical Institute’s Janelia Research Campus, in Virginia, had connections with world-class neuroscientists who shared his vision of building a new kind of probe for neuron-level observation of living brains.

Dutta and Harris recruited allies from their institutions and beyond. They raised US $10 million from the HHMI, the Allen Institute for Brain Science in Seattle, the Gatsby Foundation, and the Wellcome Trust to fund the intensive R&D needed to produce a working prototype. Dutta led the effort at Imec to tap into semiconductor technology that had been inaccessible to the neuroscience community. Imec successfully delivered the first generation of Neuropixels probes to some 650 labs globally, and the second generation is due to be released in 2022.

In addition to a vibrant open-source community that sprang up to develop software to analyze the large data sets generated by these brain probes, the Allen Institute has created OpenScope, a shared brain observatory to which researchers around the world can propose experiments to test hypotheses about brain function. “Think of us as being the Intel of neuroscience,” Dutta says. “We’re providing the chips, and then labs and companies and open-source software groups around the world are building code and doing experiments with them.”