Those who lost the ability to see, hear, walk or grab are highly reduced in their quality of life. Science Fiction shows us many possible solutions for these kind of problems. One example is the replacement of disturbed functions by fully functional technical substitutions. Through the fast progress in technology, this fictional idea becomes more and more reality. Our research group tries to contribute its share to this development.
These kind of functional prostheses require to interact with the central nerves system. Information needs to be extracted from the neuronal activity of the brain and, depending on the field of application, information needs to be integrated into the ongoing information processes of the brain. For such a bi-directional interface to the brain, two mayor components are essential.
- First, a technology is necessary that allows to physically interface the neuronal substrate and measure and/or apply electrical gradients. For real medical applications, this has to be done in a safe way over a very long time. Higher spatial and temporal resolution of such a system, results normally in a better information transfer rate which allows to build better neurotechnological devices. The focus in our group lies on so called invasive interfacing. Therefore a surgical procedure is used to bring parts of the recording/ stimulation system in direct contact with the brain itself.
- Second, we need to understand the language of the brain. It is highly important to understand how the relevant information is stored in the electrical neuronal activities. Due to the complexity of the brain, the transformation between pieces of information and neuronal activities is typically also complex and not straightforward. Furthermore, this mapping is often depending on the actual information processing state of the neuronal circuits. For example, the neuronal coding of a visual stimulus may change whether it is attended by its observer.
In the year 2009, the Bundesministerium für Bildung und Forschung (BMBF) funded the project "Innovationswettbewerb Medizintechnik - Kabellose Erfassung lokaler Feldpotentiale und elektrische Stimulation der Großhirnrinde für medizinische Diagnostik und Neuroprothetik" (short Kalomed). Klaus Pawelzik is coordinator of this joint research project. Member of this cooperative project are the groups of Andreas Kreiter, Walter Lang, Steffen Paul, and Martin Schneider of the University of Bremen as well as the group of Christian Elger (Epileptologie, University of Bonn) and the company Brain Products.
A problem for neuro-technological applications is to record the neuronal activity patterns in high spatial density over a long time (like a life time). For acquiring the required spatial and temporal resolution, it is necessary that the electrodes (interface between the recording system and neuronal substrate) are placed as near as possible to the neuronal circuits. The electrodes need to be placed at least under the skull of the patient. From this a problem arises: How can the implanted electrodes be connected to an external recording system? Cables as connectors cause problems because they run through the bone and create channels which allow bacteria to travel into the head of the patient. This bears a high risk for an infection. Furthermore, the cables that exit the body generate an additional high mechanical risk. If the cables get stuck and are pulled on, this can create severe injuries.
Goal of this project is the development of a fully implantable wireless recording system. The idea is to develop a very small system that collects energy wireless as well as communicates with the external world wireless that doesn't show the problems of a system with cables.
Research Focus Neurotechnology
The university of Bremen decided in 2009 that neurotechnology is an important research direction. This lead to the installment of a new research focus. Under the coordination of Axel Gräser seven research groups are working on basic research question in the field of neurotechnology. Beside the group of Axel Gräser, our group and the groups of Canan Basar-Eroglu, Andreas Kreiter, Walter Lang, Steffen Paul, and Martin Schneider participate in this interdisciplinary research focus.
In our project, we try to explore the possibilities of selective visual attention as information source for brain computer interfaces (BCI). The idea is to visually attend one object from a set of shown objects without moving the gaze and, based on recorded neuronal activity pattern, reconstruct which of the shown objects was selected. This can be used to build an interface, like a so called BCI- speller, that allows handicapped persons to communicate with other people or to control external devices.
From 2002 to 2006 the Bundesministerium für Bildung und Forschung (BMBF) funded the DIP METACOMP (Models and Experiments towards Adaptive Control of Motor Prostheses) initiative. A problem for neuronal prostheses are non-stationarities. Due to neuronal plasticity, degeneration of the recording electrodes or mechanical perturbations, the mapping between intended actions (like movements) and the neuronal activity patters may change over time. This is a problem for a prosthesis that interprets these patterns and tries to reconstruct the said intended action. In cooperation with Eilon Vaadia (University of Jerusaelm) and Ad Aertsen (University of Freiburg), we developed algorithms for online-adaption of neuro-prostheses control systems. Based on the actual performance of the prostheses, the online-adaptation tries to find better settings which improves the performance of the system. [Publication]
Furthermore, we developed in cooperation with the Fraunhofer-Institut für Mikroelektronische Schaltungen und Systeme IMS and Andreas Kreiter (University of Bremen) a completely wireless implantable one-channel recording system (see figure).