A UNSW biomedical expert explains how neurostimulation can already treat conditions like chronic pain, Parkinson's disease and hearing loss - and why the next generation of smarter devices could transform medicine.
From restoring hearing to easing chronic pain, devices that interact directly with the nervous system have been part of medicine for decades.
Technologies such as cochlear implants, deep brain stimulation and spinal cord stimulation are no longer experimental - they are well-established clinical tools that have improved the lives of millions of people worldwide.
But these technologies are rapidly evolving. Advances in electronics, materials science and data processing are allowing researchers to find new applications, stimulate with greater precision, and design systems that respond dynamically to the body rather than operating continuously.
Known as neurosensing and neurostimulation, these technologies aim to read and influence the electrical signals that govern how our bodies move, feel and function.
When combined in a single system, they form what is known as closed-loop neuromodulation - devices that can sense neural activity and adjust stimulation in real time.
While the ideas may sound like science fiction, some of these next-generation devices are already changing lives. And their impact is likely to grow significantly in the next decade.
At its simplest, the nervous system works by sending electrical signals between the brain, spinal cord and nerves. Closed-loop neuromodulation technologies are designed to interact with those signals.
Neurostimulation involves sending carefully controlled electrical impulses into specific parts of the nervous system to restore or regulate function, an approach that has been used clinically for decades, but is now being applied in increasingly sophisticated ways.
"All functions of the body are controlled by the brain, spinal cord and the nerves," says Associate Professor Mohit Shivdasani , chair of the upcoming Australasian Bioelectronics, Neurosensing and Neuromodulation Symposium , being hosted by UNSW from February 16-18.
"Unfortunately, sometimes these nerves or the brain doesn't send the right message, or there's a disease or trauma that affects a certain function.
"What decades of research, and real-world devices already in use, have shown is that if you send information to those nerves in the form of an artificial input, you can either restore function in specific areas of the body or treat underlying conditions affecting them.
"In some cases, these devices can work almost like flipping a switch, where symptoms caused by the underlying condition are dramatically reduced as soon as stimulation begins."
Neurosensing, by contrast, focuses on recording signals from the nervous system. These signals can reveal information about movement, pain, inflammation or even speech intentions.
Together, sensing and stimulation form the foundation of modern closed-loop neuromodulation the targeted control of neural activity.
How do these technologies work?
Neurons communicate using tiny electrical pulses. Closed-loop devices use in-built electrodes to detect those signals, while also delivering electrical currents to influence them, typically through the same electrodes.
Precision is critical: deep brain stimulation, for example, targets areas just a few millimetres wide, located several centimetres beneath the brain's surface.
Many neurotechnologies are already well established. Cochlear implants, which stimulate the auditory nerve, allow people who are profoundly deaf to perceive sound.
They are now approved for use in infants as young as six months, dramatically improving language development.
Other applications include:
- Deep brain stimulation for Parkinson's disease, reducing tremor and movement difficulties, as well as other neurological conditions
- Spinal cord stimulation for chronic neuropathic (nerve-related) pain
- Vagus nerve stimulation for epilepsy and inflammatory conditions
Current closed-loop neuromodulation devices
Of these, deep brain stimulation and spinal cord stimulation devices have already become closed-loop where they both sense and stimulate, marking an important step toward a new generation of smarter, more responsive implants.
The continued miniaturisation of electronics and improvements in materials science is expected to make implants ever-smaller, longer-lasting and more compatible with the body.
For the general public, this could mean more effective treatments with fewer side effects, longer device lifespans, and less invasive procedures.
In many cases, the results can be immediate. People with severe tremors or pain may experience relief as soon as the device is switched on.
For people with Parkinson's disease, deep brain stimulation can instantly and dramatically reduce tremors, stiffness, and movement freezing.
But it is important to understand that neurostimulation is not repairing damage inside the body, simply helping patients better deal with the impacts.
"It's never a cure for the underlying condition, but it can give back significant quality of living for most implant recipients," says A/Prof. Shivdasani from UNSW's School of Biomedical Engineering .
These technologies offer something few other treatments can: restored independence.
In many ways, the future of neurostimulation is less about reinventing the technology, and more about refining it - making it more precise, more adaptive, and more closely aligned with each patient's needs.
Neurosensing is also advancing through brain-computer interfaces (BCIs), which record neural signals to allow people with paralysis to control computers or communicate.
While most BCIs are still in clinical trials, early studies show they can decode intended movement or speech directly from the brain. For people with paralysis or severe motor impairment, this could allow direct interaction with computers, smartphones, or communication devices via their thoughts alone.
Non-invasive versions, using external sensors to record brain activity, already exist. More invasive systems, where electrodes are implanted near specific brain regions, are still in clinical trials.
Beyond treatment, neurosensing is deepening scientific understanding of how the brain works. Each improvement in sensing accuracy helps researchers decode how neural circuits process information, paving the way for better therapies.
What are the main challenges?
Given the way the technologies interact with complex areas of the body, the technical challenges are unsurprisingly demanding.
For instance, the brain is extraordinarily complicated and does not tolerate foreign objects easily. Preventing immune reactions, filtering out neural "noise", and ensuring precise targeting are all ongoing areas of research.
One of the biggest technical hurdles is precision. In deep brain stimulation, surgeons have to target regions just a few millimetres across, located up to 10 centimetres inside the brain.
Another obstacle to advancement is simply time. Developing these types of medical devices can take over a decade, compared with just a few years for consumer technology.
Public perception is also another hurdle. While people with severe illness may embrace implants, others may feel uneasy about allowing devices to be implanted that interact with their brain.
"We're not thinking about super-humans. Humans are complicated enough. What we're doing is helping people who need it," says A/Prof. Shivdasani.
"Personally, working in this area, I feel humbled. But I am also excited that there's always something more to discover."
