NeuroCIMT Project 8: Invasive Sensing

Sensorimotor Integration in the Human Brain

Looking at the brain in more detail

The brain’s organisation is very detailed. Current imaging techniques to investigate neuronal processes in the brain cannot probe the brain in enough detail. This project focusses on the brain’s organisation of the motoric functions of the hand and arm. What area in the brain is responsible for what muscle contracting in what way?

Dense grid of electrodes
To be able to shed light on this matter, a new brain signal recording technique will be developed.  None of the current techniques such as EEG, ElectroCorticoGraphy or functional MRI can measure at the millimetre scale, at millisecond time resolution, which is needed to image the local organisation in real time. With new grids of electrodes, a hundred times closer together than in a conventional EEG setup, the researchers will directly probe the brain of patients who undergo awake surgery for tumour resection.

Testing directly on the brain
In the last ten minutes of the surgery before the skull is closed again, the researchers get the chance to ask the patients to perform certain movements with their hands, fingers, and wrists, and subsequently record the resulting neuronal activity with the new technique. At the same time, people will work on a model to translate movement into individual muscle contractions. What muscle needs to contract to what extent to make a certain movement possible? Newly developed algorithms will tie together the brain measurements to the muscular model, to be able to link brain patterns to limb movements.

Brain Computer Interface
The knowledge gained by this project can for example lead to new types of brain computer interfacing implants. The researchers envision a system consisting of a brain implant to measure brain activity, wirelessly coupled to a microchip implanted in the wrist. The electrodes measure the brain activity and send the signal to the microchip, which translates it in a stimulus causing the right muscle to contract.

Unknown territory
Another part of the project is more exploratory by nature. A different kind of electrodes, wires with multiple contact points, will also be used to try and measure signals from the brain sulci (folds in the brain). Since these folds are difficult to access without risking damage (many blood vessels cross over within sulci and can cause bleeding when electrodes are moved inside), that is an area no one has ever explored before. But together they form the largest surface area of brain material. Although it is yet not known whether there indeed will be interesting signals to be detected in those areas, this can turn out to be a promising new field of research.

Application perspective
Michel Decré, Director Research and Technology at Medtronic
‘We are developing leads which contain up to forty electrodes, instead of the four electrodes used in current medical applications such as Deep Brain Stimulation for Parkinson’s disease. This project is a good way to explore new applications for this technology. If we should indeed succeed in measuring useful signals within the sulci of the brain, this opens up a whole new range of less invasive sensing and stimulating possibilities. It would be great if we could use these for example to enable people with neuroprostheses to gain more control over their artificial limbs or to regain some control over their natural limbs.’

Cortec, Delft University of Technology, Medtronic, Radboud University Nijmegen, University Medical Center Utrecht