Date: 25 June 2025
What happens when a medical device meets the brain? A study from CÚRAM Research Ireland Centre for Medical Devices has shed light on how electrical signals from implanted electrodes pass to living brain tissue, and has shown important findings to consider for device safety in next-generation devices.
Deep Brain Stimulation (DBS) and other neuromodulation technologies place electrodes in the brain to sense and stimulate electrical activity of nerves. This can deliver life-changing results for patients, for example stopping tremors and enabling patients to move more freely in Parkinson’s Disease.
The new findings suggest that DBS electrodes may transfer charge in a nonlinear fashion, even at the upper end of stimulation levels used in the clinic, which could affect the device’s performance.
The findings, published in Journal of Neural Engineering, draw on computational and wet-lab data to build a more detailed model of the electrode-tissue interface, and take into account factors often overlooked in current DBS models.
“The interface between the electronic device and the living tissue is complex,” says Professor Madeleine Lowery, CÚRAM Investigator from the Neuromuscular Systems Lab at University College Dublin School of Electrical and Electronic Engineering.
“As researchers, we use computational models to help us understand how the current is likely to behave as it transfers from the device to the tissue, but these models make some assumptions and simplifications, so we set out to do a deeper dive into what happens at that interface between the device and the brain as the current transfers.”
The study, which was supported by Research Ireland and the European Research Council, combined computational model simulations with wet-lab observations on rat brain tissue, and explored the behaviour and impacts of currents across a range of levels.
“When operating at relatively low levels of current, such as the ones used in the clinic, it is assumed to be a linear relationship, so that if you increase the current, the voltage will increase proportionally and vice versa,” explains Professor Lowery.
“But our results suggest that when you increase the current above beyond a certain threshold, there is a nonlinear response at the interface between the electrode and brain.”
The study suggests that a nonlinear response can alter how current spreads in the brain and increase neural activation, compared to the present assumptions. The threshold beyond which the interface enters a nonlinear regime occurs at relatively low stimulation levels.
Based on the findings, the researchers estimate that the nonlinear threshold could occur at the upper boundary of clinical settings, raising important considerations for both commercial device design and clinical programming strategies for future devices.
“When designing future medical devices manufacturers need to be aware of the relatively low level of stimulation at which nonlinearities can arise, and the potential implications that it can have when developing new stimulation protocols to provide the optimal treatment for patients.” concludes Professor Lowery.
Working on the project under the supervision of Prof Lowery were doctoral candidate Karthik Sridhar and postdoctoral researcher Dr Judith Evers.
ENDS
