A. The Gertrude Project: Real-Time Visualization of Pig Brain Signals

On the afternoon of Friday, August 28, 2020, Neuralink's headquarters in Fremont, San Francisco, was filled with an unusual scene. Behind the stage sat a small pen lined with hay. When Elon Musk appeared, running behind schedule, and addressed the audience, no one was expecting a new electric car or rocket. The stars of the day were three pigs.

The curtain opened to reveal a pink-skinned animal snuffling through a pile of hay. Every time the pig named Gertrude buried her snout in the hay, a strange sound poured from the speakers. "Dee-dee-dee-dik, brrreep." It sounded like erratic jazz, or the crackling noise of an old modem trying to connect. Musk explained what the sound was. "What you're hearing is the real-time firing of neurons inside Gertrude's brain."

Two months earlier, a coin-sized chip had been implanted in Gertrude's skull. The device was connected to the cortical region responsible for snout sensation, and every time the pig smelled or touched something, it captured the resulting neural signals and transmitted them wirelessly. Blue waveforms danced across the screen. Spikes shot upward each time her snout moved. The brain's invisible electrical whispers had been converted into a physical signal you could hear with your own ears.

But the real significance of this demonstration did not lie in the fact that it could read brainwaves. The point was in the comparison.

Musk introduced the three pigs one by one. The first pig, Joyce, had never received an implant and was in her completely natural state. The second pig, Dorothy, had once had a chip implanted in her brain, which was later removed. Dorothy's presence carried a clear message: if you get a Neuralink implanted and change your mind, or want an upgrade, it can be removed at any time with no harm to brain function. This proved reversibility. The last to appear was Gertrude, who was currently living with a chip in her brain. Looking at her from the outside, there were no visible scars, no abnormal behavior.

Why pigs, of all animals? In neuroscience research, primates are the closest model to humans. But the thickness and density of a pig's skull closely resemble those of a human skull, making pigs ideal for testing the surgical robot's drilling and implant

fitting procedures. The sensory cortex that controls a pig's snout is remarkably well developed. The massive volume of neural information generated when a pig explores the world through its snout provided ideal data for testing the performance of a brain-computer interface.

The research team also demonstrated an algorithm that analyzed brain signals generated while Gertrude walked on a treadmill and predicted the position of her leg joints. Two lines appeared on the screen. The gray line tracked the actual movement of the pig's legs, and the blue line showed the values predicted from brain signals alone. The two lines matched almost perfectly. This was a mathematical demonstration that it might be possible to decode motor cortex signals and restore movement to the paralyzed legs of spinal cord injury patients.

Musk called the device a "Fitbit in your skull." It sounded like a marketing slogan, but what Gertrude showed was that the metaphor could become reality. She ate her meals, slept, and socialized with her companions in an ordinary daily routine, all while transmitting her brain data wirelessly around the clock. Compared to earlier brain experiments conducted in isolated lab environments with thick wires plugged into the skull, this was a fundamental shift.

Stanford neuroscientist Sergey Stavisky watched the presentation and described Neuralink's progress from its early 2019 demonstration to a fully implanted system in 2020 as "impressive and substantive advancement." Graeme Moffat, a neuroscience researcher at the University of Toronto, said the chip represented "a leap beyond existing science" in terms of size, portability, and wireless capability. Of course, this presentation was a demo, not a scientific paper, and questions of clinical rigor, such as sample size, follow-up duration, and how side effects were defined, remained separate issues.

Still, the effect of the Gertrude demo was unmistakable. It showed that brain-computer interfaces were no longer confined to the realm of noninvasive EEG headsets; invasive implants, too, were moving toward a form factor suitable for real-world use. For the public, the demonstration planted two feelings at once. One was a sense of wonder that even the brain, the most intimate territory of a living being, could be turned into data. The other was a chilling awareness that one's own thoughts and sensations could be converted into electronic beeps just like that.

Gertrude had no idea she was carrying the weight of humanity's future. She was just snuffling around for tasty hay. But the electronic sounds that rang out from her snuffling were a signal flare, announcing that neural engineering had left its ivory tower and entered the territory of commercial, practical reality. The sound that came from a pig's brain was a preview of a future in which the human brain would speak directly to machines.

B. Pager's Pong Game: Playing a Video Game with Thought Alone

On April 8, 2021, a three-minute, twenty-seven-second video appeared on YouTube. On screen sat a nine-year-old macaque monkey in front of a monitor. His name was Pager. He was holding a joystick and playing a video game. Banana smoothie flowed from a metal straw, and Pager sipped it eagerly while staying focused on the game. Up to this point, it looked like a routine animal cognition experiment.

Then, a moment later, the narrator said: "We've now disconnected the joystick."

The joystick's cable was unplugged. But the ping-pong ball on the monitor kept moving exactly as Pager intended. Pager was still going through the motions of moving the joystick with his hand, but what was actually controlling the game was not his hand. It was his brain. At the video's climax, the researchers removed the joystick entirely. Pager stared at empty space while sipping smoothie through his straw. His hands rested still on his lap. Yet the paddle on the monitor was returning volleys at fierce speed with pinpoint accuracy. This was MindPong.

Elon Musk shared the video on Twitter and wrote: "A monkey is literally playing a video game telepathically using a brain chip." Telepathy is not a scientific term, but it was the most fitting literary expression for what was happening. The transmission of thought. The relay of will, bypassing the body entirely.

Behind this seemingly magical scene lay meticulous engineering. Six weeks before the demonstration, two Neuralink N1 chips had been implanted in Pager's brain, one in each side of the motor cortex. A total of 2,048 electrodes recorded the firing patterns of neurons whenever Pager attempted to move his hands and arms.

The first step was calibration. While Pager physically moved the joystick to play the game, the computer paired his joystick movements with his brain signals and learned. "When this pattern of electrical signals appears, the joystick was pushed up." "When that pattern appears, it was pushed down." The artificial intelligence identified these correlations.

Once the learning was complete, no physical input device was needed. Neuralink's decoder intercepted the signals from Pager's brain in real time and translated them into cursor movements. At the bottom of the video, Pager's brain activity was visualized. Each time red spikes surged, the in-game paddle responded instantly. The latency was nearly imperceptible.

For Pager, this process required no special effort. He simply wanted to keep drinking banana smoothie and intended to hit the ball. That intention, without passing through any wire or muscle, was directly converted into action in the digital world.

Andrew Jackson, professor of neural interfaces at Newcastle University, noted that controlling a computer cursor with a monkey's brain was not a new concept in itself. A similar demonstration was first published in 2002, and the idea traces back to Eberhard Fetz's research in the 1960s. But the point where Neuralink delivered a shock was elsewhere. It compressed fully wireless operation, a miniaturized implant, and high-channel-count real-time decoding into a single video.

With conventional noninvasive EEG equipment, only simple commands like "left or right" could be issued, and response times were slow. But Pager, through high-resolution signals at the individual neuron level, demonstrated smooth, precise analog control, as if gripping a mouse.

The experiment also confirmed the power of neuroplasticity. Pager understood the rules of the game and learned that his brain activity led to game outcomes (and smoothie rewards). Just as Hebb's rule states that "neurons that fire together wire together," Pager's brain rewired itself through interaction with the machine, forging an optimal control pathway.

Musk shared the video with a bold prediction: "Eventually, a paralyzed person will be able to operate a smartphone faster with their brain than someone using their thumbs." Pager's Pong game was not mere entertainment. It was a message of hope for people with quadriplegia. It proved that even someone who cannot move a single finger because of a severed spinal cord could operate a computer like Pager, as long as the motor cortex remains alive.

But the video also left behind questions that go beyond technical achievement. Was Pager playing the game, or had he become part of the game? Where is the boundary between his consciousness and the computer's algorithm? Watching a monkey use its brain for the reward of a smoothie, were we catching an early glimpse of a future in which humans connect their brains to machines in pursuit of dopamine? The glow of the monitor reflected in Pager's eyes was a striking metaphor for the dawn of a posthuman age, where human and machine become one.

C. Technical Achievements and Safety Data from Animal Experiments

Behind the flashy demonstrations of Gertrude the pig and Pager the monkey lay a mountain of data that Neuralink engineers had accumulated over years. The real purpose of animal experiments was never showmanship. It was to prove that this technology, once placed inside a human brain, would not kill the patient, would last a long time, and would actually work. This was a survival struggle: semiconductor hardware fighting to stay alive in the brutal battlefield of a biological environment.

The engineering achievements Neuralink pushed hard on can be grouped into four categories.

The first was the high-density channel design based on electrode threads. The conventional rigid Utah Array caused microscopic damage to brain tissue and triggered immune responses, degrading signal quality over time. Neuralink had to prove through animal testing that its thin polyimide thread electrodes could flex with the brain's subtle movements while resisting corrosion in cerebrospinal fluid and blood, maintaining function for years.

The second was the R1 surgical robot, built to insert these electrodes quickly and precisely. The brain's surface is covered with tiny blood vessels. Puncture one during electrode insertion and cerebral hemorrhage follows, leading to brain cell death. According to data Neuralink released, the R1 robot scanned the brain surfaces of pigs and monkeys and automatically calculated paths that avoided blood vessels. It inserted 192 electrodes per minute while maintaining micrometer-level precision. The complication rate was far lower than what human surgeons achieved inserting electrodes manually under a microscope.

The third was the integration technology that handled ultra-low-power signal amplification, digitization, and wireless transmission all inside the implant itself. The interior of the body, the brain in particular, is hell for electronics. Temperature sits at 36.5 degrees Celsius, humidity is high, and corrosive bodily fluids surround everything. Many early BCI devices corroded or lost insulation within months and broke down. Neuralink validated its chip sealing technology through accelerated aging tests and actual animal implantation. Monkeys like Pager lived with the chip implanted for over a year, and during that period no toxic reactions from infection or device corrosion were reported.

The fourth was the real-time decoding pipeline. Gertrude's leg joint prediction and Pager's Pong game control served as indicators of how precise the brain signal decoding algorithm had become. Neuralink succeeded in analyzing signals from 1,024 channels in real time and extracting intention. Noise removal from firing data across hundreds to thousands of channels, nonlinear pattern recognition, minimization of time delay: these demanding signal processing problems were solved within real-time constraints.

But safety data cannot be fully conveyed through demo videos alone. Safety encompasses surgical complications, post-implant biological responses, long-term durability, pain and stress management from an animal welfare perspective, and research governance. In published academic and official documents, Neuralink presented some figures and system overviews, but outside researchers have repeatedly noted that the data accumulated and disclosed has not been sufficient for large-scale, long-term, reproducible verification.

In early 2022, the FDA rejected Neuralink's clinical trial application. The main concerns were lithium battery safety, the possibility that electrode threads might migrate to unintended areas within the brain, and the risk of damaging brain tissue when removing the chip. Brain tissue can suffer permanent damage from a temperature increase of just one to two degrees Celsius. Neuralink had to prove that the heat generated when the chip operated at maximum load or during charging stayed within safe limits.

Neuralink responded by generating additional animal testing data. The company demonstrated its battery overheat prevention system and showed, through a pig model (the Dorothy case), that electrodes could be safely removed without adhering to brain tissue. In 2022 pig experiments, granulomas, a type of inflammatory tissue, were observed forming in the brains of some animals. Neuralink could not identify the cause but claimed the implant and threads were not responsible.

In May 2023, the FDA approved human clinical trials based on this supplementary data. Animal experiments had been more than functional demonstrations. They were an essential gate for meeting the strict safety standards regulators demanded.

After the surgery on Noland Arbaugh, the first human patient in 2024, some electrode threads retracted from the brain. According to Reuters, both Neuralink and the FDA had known from earlier animal experiments that threads thinner than a human hair could retract. Neuralink, however, judged the risk was not serious enough to require a redesign. Starting with the second patient, the company responded by inserting the threads eight millimeters deeper into the motor cortex.

In the end, the data left behind by pigs and monkeys was not just numbers. It was the scientific foundation that elevated the idea of "drilling a hole in the skull and implanting a chip," an idea that sounds barbaric and reckless on its face, into a medically controllable and predictable procedure. Built on their sacrifice and contribution, Neuralink evolved from an eccentric lab project into a next-generation medical device.

D. The Animal Welfare Controversy and Responses to Ethical Criticism

The brighter the light of innovation, the darker the shadow it casts. Behind Neuralink's spectacular technical achievements lies a heavy ethical issue: the suffering and death of animals who ended their lives in laboratories. Starting in 2022, formal complaints from animal rights organizations and revelations from former employees posed a fundamental question about how far we are willing to go in the name of technological progress.

At the center of the controversy stood the Physicians Committee for Responsible Medicine (PCRM). Through a public records lawsuit, they obtained documents from Neuralink's early experiments (2017 to 2020) conducted in partnership with the University of California, Davis. The contents of the reports were shocking. They described monkeys euthanized after suffering extreme pain following brain surgery, cases where infection caused skin to rot away, and cases where the medical adhesive BioGlue seeped onto the brain surface, destroying brain cells and causing animals to die in seizures.

Reuters, citing testimony from internal staff, reported that Elon Musk's pressure to "speed things up" led to experiments being rushed without adequate preparation, resulting in the deaths of approximately 1,500 or more animals since 2018. Some monkeys were found with fingers and toes that had been severed. PCRM argued this was evidence of self-mutilation by animals under extreme stress.

In September 2023, Wired magazine published an investigative report based on veterinary records. According to those records, one monkey was suffering from "serious neurological deficits," yet her euthanasia was delayed at a Neuralink scientist's request. The autopsy revealed that the experiments had "deformed and ruptured her brain," and her brain was "herniating through the base of the skull." Regulators acknowledged this constituted a violation of the Animal Welfare Act.

In December 2018, two holes were drilled into a monkey's skull and electrodes were implanted. Metal plates were fastened to the head with bone screws and the skin around the implant was sutured. The surgical site quickly became infected and "the skin eroded." Three months later, with the infection persisting, they killed her. The autopsy revealed she had suffered "acute" hemorrhaging in the brain and that the cerebral cortex had been "mangled" by Neuralink's device.

Elon Musk and Neuralink responded aggressively. On the social media platform X, Musk claimed that "no monkey has died as a result of a Neuralink implant." He countered that the early implant experiments did not use healthy monkeys but were conducted on monkeys that were already in a terminal state.

But the public records PCRM obtained through litigation told a different story. Only three monkeys had been used in terminal, non-recovery surgeries. Twelve previously healthy animals were euthanized as a direct result of problems with the company's implants. In September 2023, PCRM asked the SEC (Securities

and Exchange Commission) to investigate Musk and Neuralink for securities fraud. In December 2024, reports emerged that the SEC had reopened its investigation into Neuralink.

Neuralink maintained that its animal care facility was accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC) and was designed to resemble an "animal playground" rather than a laboratory. The company emphasized that the animals were not confined but lived in spacious play areas, and that their participation in experiments was voluntary.

According to PCRM's analysis, however, the experimental protocol required monkeys to be forcibly restrained in chairs for up to five hours a day. If an animal failed to "acclimate" to the restraint, the protocol called for attaching a steel "headpost implant" to the skull to forcibly immobilize the animal's head. Neuralink claimed the monkeys willingly participated in experiments, but no animal would have voluntarily allowed an experimenter to drill holes in its skull and implant a device.

In December 2022, the USDA Office of the Inspector General opened an investigation into Neuralink. In July 2023, the USDA investigation found no evidence of Animal Welfare Act violations apart from a self-reported incident from 2019. PCRM challenged the findings. Then in November 2024, reports emerged that the FDA had discovered multiple quality control problems at Neuralink's California animal research facility. Calibration records for pH meters, vital signs monitors, and other equipment could not be located.

In January 2025, during the first week of President Trump's second administration, 17 inspectors general were fired, including Phyllis Fong, who had overseen the USDA investigation. Both investigations that PCRM had initiated were thrown into uncertainty.

The history of technology has always been written on top of ethical dilemmas. Pasteur's vaccine experiments were no different. Neither was Laika in the early days of space exploration. Neuralink took the realist position that "developing medical devices without animal testing is impossible." Gaining FDA approval and applying the technology to humans requires biological data from living animals, and current technology cannot substitute simulations for the complexity of the brain.

Yet the fundamental ethical question, "Is it justified to open the brain of a healthy animal?," has not gone away. How much suffering in other living beings will we permit to reduce human suffering? When the speed of innovation outpaces the speed of bioethics, who should press the brake, and how?

The electrodes planted in those animals' brains are not just transmitting signals. They are continuously broadcasting a question about the moral standing of the human species. The sacrifice of pigs and monkeys is regarded as a tragic but unavoidable toll for crossing into the next stage: human clinical trials. But whether the amount on that toll receipt is fair is something we must keep asking.