“Stimulation does not replace clinical work.
It is a tool that helps unlock residual potential and enables the person to make better use of what can be recovered through therapy”.
One of the world’s leading experts in neuroengineering, Micera will take part in the IFESS Annual Congress in Lecco in early September. His presentation will range from the development of implantable neural interfaces and neuroprostheses to the restoration of motor and sensory functions.
This interview marks the beginning of a four-part series featuring the leading figures of the annual congress of the International Functional Electrical Stimulation Society (IFESS), which will take place from 2 to 4 September at the Lecco Campus of Politecnico di Milano.
The first guest is Silvestro Micera, Professor of Bioelectronics at the Scuola Superiore Sant’Anna in Pisa and at the École Polytechnique Fédérale de Lausanne, where he holds the Bertarelli Foundation Chair in Translational NeuroEngineering.
One of the world’s leading experts in neuroengineering, Micera studies and develops neuroprostheses and implantable neural interfaces capable of communicating with the central and peripheral nervous systems, with the aim of restoring motor and sensory functions impaired by injury or neurological disease.
In this interview, he outlines the main areas of his research and previews some of the projects he will present at IFESS.
Professor Micera, how can electrical stimulation and neurotechnologies help the nervous system reorganize itself and recover functions impaired by an injury or neurological disease?
Neurotechnologies make it possible to establish an artificial connection with the nervous system, either by recording its activity or by stimulating it in a targeted way. In the case of a spinal cord injury, for example, electrodes can be implanted below the level of the lesion to generate electrical impulses capable of activating spinal circuits, peripheral nerves and, consequently, the muscles involved in movement.
These devices do not simply produce a movement artificially. They can also induce changes within the central nervous system and promote processes of neural plasticity, even after spontaneous recovery has reached a plateau. Our goal is to understand how to enhance and extend the nervous system’s ability to reorganize itself by combining stimulation, motor intention and sensory feedback.
This is precisely what you are doing within MINE Lab, the joint laboratory on implantable neurotechnologies led by you and Professor Pietro Mortini, where you are working to restore walking in people with paraplegia through spinal cord stimulation. How does this process work in practice?
The work is divided into three phases. The first is surgical and consists of correctly implanting the electrodes on the spinal cord. Professor Pietro Mortini and his team at San Raffaele have worked overtime to optimize the procedure and make it increasingly precise.
The second phase begins after surgery and is equally important. The device must be programmed, the electrodes to be used must be identified, the stimulation sites selected, and the stimulation parameters adjusted over time. We carry out this work together with physiatrists and physiotherapists, because the configuration must be tailored to each patient’s individual response and to the improvements they gradually achieve during rehabilitation.
The third phase is the rehabilitation pathway itself. Spinal cord stimulation is not a miracle, and it does not replace clinical work. It is a tool that we make available to healthcare professionals to unlock residual potential and help the person make better use of what can be recovered through therapy. For this reason, the parameters are not set once and for all but must be modified and optimized over time.
More than twenty patients have already received implants, and, despite all the necessary limitations and precautions, this activity is now moving towards a structured clinical practice. The key point is not simply to perform the implant, but to make it work as effectively as possible for that specific person.
One of your main areas of research concerns neuroprostheses. How do they work, and what abilities can they restore?
A neuroprosthesis is an artificial system designed to replace or restore an impaired function by interacting directly with the nervous system. In people with an amputation, for example, we can use residual muscle activity to control a prosthetic device and stimulate the peripheral nerves to restore tactile information.
Sensory feedback is essential. When we walk, receptors in the foot continuously send information to the brain about pressure, limb position and the characteristics of the terrain. Artificially reproducing this information allows the person to control the prosthesis more effectively, adapt their movement and reduce the risk of falling.
The aim is to move from experimental systems used temporarily in the laboratory to fully implantable, stable devices that can be used in everyday life and are capable of transmitting information about touch, position and even temperature.
Are you also working on systems capable of directly interpreting a person’s intention to move?
Yes. We are developing systems that record activity in the cerebral cortex and decode the user’s intention. The idea is to create a circuit made up of several interconnected nodes: the system recognizes that the person wants to perform a specific movement, artificially bypasses the point at which neural communication has been interrupted and transmits the command below the level of the lesion, activating the muscles required.
To truly close the loop, however, reading motor intention is not enough. The sensory information generated by movement must also be returned to the brain. The goal is therefore to develop bidirectional systems capable both of interpreting commands from the brain and of transmitting tactile and proprioceptive sensations back to it.
This is an extremely complex challenge, because the nervous system is not a simple network of connections. Nevertheless, over the past twenty years we have developed increasingly effective tools for recording and stimulating the cerebral cortex, deep brain structures, the spinal cord and peripheral nerves.
What are currently the main obstacles to transferring these technologies into clinical practice?
The first challenge is technological. Electrodes must be biocompatible, selective and capable of functioning for many years without damaging tissue. They must establish very precise contact with the neural region that needs to be stimulated or recorded from, while limiting the involvement of surrounding areas as much as possible.
A second issue is personalization. A spinal implant may contain dozens of electrodes, and, after surgery, it is necessary to identify which contacts, and which combinations produce the best motor response in the individual patient. Today, this phase is still largely carried out manually, but artificial intelligence may accelerate device configuration and reduce the time required to achieve functional recovery.
Finally, there are major clinical, ethical and organizational issues. We work with people in medically fragile conditions and must provide robust evidence of safety and efficacy.
These projects also require close collaboration among bioengineers, neurosurgeons, neurologists, physiatrists and physiotherapists. No single discipline can address such a complex challenge alone.
At the IFESS congress, you will also present a “soft” exoskeleton designed for people with spinal cord injury. What does it consist of, and what prospects does it open up for rehabilitation?
It is an exoskeleton developed by my colleague Tommaso Proietti, Tenure-Track Assistant Professor (RTT) at Scuola Superiore Sant’Anna and head of the Soft NeuroBionics Lab within the Bioelectronics and Bioengineering Area. It is based on soft pneumatic actuators, similar to small balloons, which inflate to assist movement of the arm. Unlike traditional rigid exoskeletons, this system is lightweight, flexible and can adapt more easily to the person’s body. We have already tested it in patients with tetraplegia, with published results, and we are continuing our work to further assess its effectiveness.
The aim is not only to use it during rehabilitation sessions, but to turn it into a device that can be provided to patients and used at home.
Moving from the research environment into everyday life is crucial. A technology becomes truly useful when it can support the person over time and in the contexts in which they live.
Another topic of your presentation will be the recovery of hand function. Which technologies are you working on?
We are pursuing two complementary directions. The first concerns hand prostheses capable of restoring sensory feedback. The aim is to develop a fully implanted system that can transmit information about touch, hand position and temperature. Over the next few years, we hope to test an implant that patients can use reliably at home, assessing its performance not only in the laboratory but also in everyday life and over extended periods.
The second line of research concerns peripheral nerve stimulation to restore fine finger movements. Spinal cord stimulation can support broader movements of the upper limb, but it is not sufficiently selective to reproduce precise actions such as grasping. By directly stimulating the peripheral nerves, we can instead try to activate the muscles involved in finger movements in a more targeted way.
These projects illustrate the direction of our research: developing systems that are increasingly selective, personalized and usable outside the laboratory, capable not only of generating movement but also of restoring functional control and, where possible, sensory perception.
