The six territories of neuroengineering
"Brain waves" is one small corner of the field. Here is the whole map, and the careers each part leads to.
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Put an electrode on someone’s scalp and you record a few tens of microvoltsMicrovolt (µV)One millionth of a volt. Scalp EEG is tens of microvolts; a AA battery is 1.5 million of them. Glossary entry of blurred, summed activity from millions of neurons. Put a needle a millimetre into their cortex and you hear single cells fire. Put a pulse of current into a nerve and you change what the brain does rather than listening to it. These are three different fields with three different careers, and “I’m interested in brain waves” does not yet say which one you mean.
Neuroengineering has six territories. Each one has its own instruments, its own literature, and its own employers. This site visits all six, in a particular order, and by the end of Phase 2 you should know which one feels like home.
Non-invasive sensing
EEGElectroencephalography (EEG)Recording the brain's electrical activity from electrodes on the scalp, a few tens of microvolts of blurred, summed cortical activity. Glossary entry on the scalp, fNIRSFunctional near-infrared spectroscopy (fNIRS)Shining near-infrared light through the scalp and measuring how much comes back to estimate blood oxygenation in the cortex underneath; a pulse oximeter pointed at the brain. Glossary entry with near-infrared light, MEGMagnetoencephalography (MEG)Recording the tiny magnetic fields produced by cortical currents with superconducting sensors in a shielded room; less blurred by the skull than EEG, and far more expensive. Glossary entry in a shielded room. Nothing enters the body. The signals are small and blurry, the equipment ranges from a fifty-dollar board to a multi-million-dollar magnetometer array, and this is where hobbyists can do real work.Almost everything in Phases 1 to 3 lives here, because it is the territory you can enter from a dorm room.
Careers: consumer neurotech (sleep headbands, focus trackers), clinical EEG and sleep medicine, epilepsy diagnostics, non-invasive brain-computer interfaces, research amplifiers.
Invasive interfaces
ECoGElectrocorticography (ECoG)Recording from electrodes placed on the surface of the brain under the skull, usually during epilepsy surgery evaluation; cleaner and sharper than EEG. Glossary entry grids on the brain’s surface, intracorticalIntracortical recordingRecording from tiny electrodes inserted into the cortex itself, close enough to hear individual neurons. Glossary entry arrays like the Utah ArrayUtah ArrayThe 10-by-10 grid of 1.5 mm silicon needles invented at the University of Utah, the electrode in nearly every human intracortical BCI study to date. Glossary entry pushed into cortex, stentrodesStentrodeSynchron's electrode array mounted on a stent and delivered through a blood vessel to sit against the motor cortex without open surgery. Glossary entry delivered through blood vessels. The signals are clean enough to hear individual neurons and to decode speech from a paralyzed person. The cost is surgery, the foreign body responseForeign body responseThe scarring the body builds around an implant, which insulates electrodes and degrades recordings over months to years. Glossary entry, and a regulatory path measured in decades.
Careers: the BCI companies (Blackrock, Neuralink, Synchron, Paradromics, Precision), academic BCI labs, neurosurgical research.
Neuromodulation
Instead of listening, you talk. Deep brain stimulationDeep brain stimulation (DBS)Electrodes implanted deep in the brain and pulsed continuously, the standard treatment for advanced Parkinson's disease and essential tremor. Glossary entry for Parkinson’s, spinal cord stimulationSpinal cord stimulation (SCS)Electrodes over the spinal cord, long used for pain and now being used to restore stepping after spinal cord injury. Glossary entry for pain and now for walking, vagus nerve stimulationVagus nerve stimulation (VNS)A cuff electrode on the vagus nerve in the neck, pulsed for epilepsy, depression, and now stroke rehabilitation. Glossary entry, cochlear implantsCochlear implantThe most successful neural prosthesis: an electrode array in the inner ear that stimulates the auditory nerve in up to 22 bands. Glossary entry, TMSTranscranial magnetic stimulation (TMS)A coil on the head that induces currents in the cortex with a brief magnetic pulse; approved for depression, and only for lab use with a trained operator. Glossary entry, focused ultrasoundFocused ultrasoundConcentrating sound energy deep in the brain to modulate or destroy tissue without opening the skull. Glossary entry. This is by far the largest commercial market in the field and the least glamorous, which means the least crowded.
Careers: Medtronic, Boston Scientific, Abbott, LivaNova, Nevro, Cochlear, NeuroPace, and a long tail of startups; clinical engineering in movement disorder and pain clinics.
Peripheral nerve and muscle
EMGElectromyography (EMG)Recording the electrical activity of muscles, hundreds of microvolts to millivolts, much larger than EEG. Glossary entry from muscles, nerve cuffs, myoelectricMyoelectric prosthesisAn artificial limb controlled by EMG from the remaining muscles. Glossary entry prosthetics, hapticHaptic feedbackInformation delivered through touch, such as vibration on the skin that tells a prosthesis user how hard they are gripping. Glossary entry feedback. Neuro-adjacent, with signals a thousand times larger than EEG, and the fastest route from an idea to a working prototype. The wristband that reads your hand gestures from forearm EMG is this territory.
Careers: prosthetics companies, Meta’s EMG wristband team, rehabilitation engineering, the University of Utah’s own NeuroRobotics lab.
Computational neuroscience
The models: how a neuron produces a spike, how populations encode movement, how a decoderDecoderThe algorithm that maps neural signals to intended actions, such as a classifier or a Kalman filter. Glossary entry should be built. Traditionally academic, and increasingly hired by BCI companies because the decoder is where the product lives.
Careers: PhD-track research, decoder and algorithm teams at every company above, a route into machine learning more broadly.
Cellular and molecular
Patch-clamp recordingExtracellular recordingRecording with an electrode near neurons rather than inside one; you see small, fast blips from nearby cells rather than the full membrane swing. Glossary entry from single cells, optogenetics, organoids, electrode materials tested against living tissue. Lab-bound and PhD-shaped, but it is where the next generation of interfaces is being designed, and the University of Utah’s nanofab sits at its edge.
Careers: academic neuroscience, electrode and materials development, pharmaceutical neuroscience.
The territories overlap on purpose
A speech-decoding BCI is invasive interfaces (the array), computational neuroscience (the decoder), and neuromodulation (if it stimulates for feedback). A sleep headband is non-invasive sensing and consumer product design. Almost every real job sits at a boundary, and the people who are valuable are the ones who can hold two territories at once: the hardware person who understands the decoder’s needs, the modeller who has held an electrode.
Deep dive Where the money and the people are 4 min
Rough sizes, to calibrate expectations. Neuromodulation is a market in the tens of billions of dollars a year and employs tens of thousands of engineers. Invasive BCI, as of this writing, has implanted well under a hundred people worldwide across all companies and is funded by venture capital and government grants rather than revenue. Non-invasive consumer neurotech has sold millions of devices, most of which sit in drawers. Computational neuroscience is mostly academic, with a few hundred industry positions.
This matters for a career plan. The dramatic results are in invasive BCI; the jobs are in neuromodulation; the fastest learning is in non-invasive sensing and peripheral work. A sensible path learns in the third, aims at the first, and keeps the second as the fallback that is also a good life.
Deep dive The Utah connection 2 min
The Utah ArrayUtah ArrayThe 10-by-10 grid of 1.5 mm silicon needles invented at the University of Utah, the electrode in nearly every human intracortical BCI study to date. Glossary entry, the electrode in nearly every human intracortical study to date, was invented at the University of Utah. Blackrock Neurotech, which makes it, and Ripple Neuro, which makes research recording and stimulation systems, are both in Salt Lake City. The university has a nanofab where new electrodes are made, a rehabilitation hospital built around technology, and an epilepsy unit. The Utah map lists all of it. A student in Salt Lake is unusually close to the physical center of two of the six territories and almost nobody there acts like it.
Explain to a friend outside engineering what the difference is between listening to the brain and talking to it, with one example of each.