How can I improve the practical work of prosthetics

Health Industry BW

Every movement we make - every grip and every step - has its origin in the brain. The aim of Carsten Mehring and his working group at the Bernstein Center for Computational Neuroscience and at the institute is to use the signals from the brain to control prostheses or to operate a computer, in order to create the basis for the development of prosthesis control for severely paralyzed patients for Biology I from the University of Freiburg.

Together with colleagues from the University Medical Center in Freiburg, the scientists were able to show that continuous arm movements can be predicted with the help of electrodes placed on the surface of the brain. The work will be published in the January issue of the journal "Journal of Neuroscience Methods" (Journal of Neuroscience Methods, 2008 Jan 15 167/1 pp. 105-114. Doi: 10.1016 / j.jneumeth.2007.10.001). Mehring's scientists used a so-called "semi-invasive" method, electrocorticography (ECoG), to measure electrical signals from the brain. "We are looking for an optimal compromise between fully invasive and non-invasive methods," explains Mehring. In non-invasive methods such as the EEG, electrodes are attached to the scalp. The neural signal is measured on the top of the skull and has a correspondingly low spatial resolution.
Left: Example of a test procedure. Test persons moved a cursor (green) with which they controlled a series of target points (yellow) on a screen. The course curve of the cursor and the target points passed in the past are not visible to the test subjects. Right: the cursor movement along the X-axis (above) and the Y-axis (below) in such an experiment (green curve). In comparison, the reconstruction of the movement from the brain activity (red curve). (Image: Carsten Mehring)
With fully invasive methods, the electrodes are implanted a few millimeters deep in the brain so that the activity of individual neurons or groups of neurons can be registered. The signal is much more accurate and enough to control complex movements. The first clinical studies on severely paralyzed patients have already been successfully carried out using this method. However, it is still difficult to say to what extent the brain can be injured by the implanted electrodes or how stable the signals measured in this way will be over a longer period of time.

With the ECoG, the electrodes are implanted directly on the surface of the brain and do not penetrate the brain tissue. They measure changes in tension on the surface of the brain that are caused by large groups of neurons. This method is less invasive and the measured signals are expected to be stable over a longer period of time. "We want to check whether this method is suitable for controlling movements and thus represents a possible alternative to fully invasive methods," explains Mehring and continues: "Our results give us hope that this could work".

Mehring carried out his research on epilepsy patients who had electrodes implanted under their skulls in preparation for brain surgery. Their brain activity was recorded while they moved to a target point on a screen by manipulating a handle with a cursor. With the help of mathematical algorithms, the scientists succeeded in extracting brain signals from these measurements that correlated with the cursor movement and with which a continuous reconstruction of the movement was possible.

In a next step, Mehring and his colleagues now want to investigate how well the strategy can be used to control a cursor on the screen with the help of neural activity without the subject moving their arm. "Previous studies show that the reconstruction of the movement from the brain signals can be improved in this way because the test person can learn to adapt his brain activity to the cursor control," says Mehring. "There is hope that, based on such methods, a prosthesis control or a means of communication for severely paralyzed patients can be developed in the future. However, many scientific and technical problems must be solved before such devices can be used in practice."

Source: Press Office University of Freiburg-January 17, 2007
The Bernstein Centers for Computational Neuroscience in Berlin, Freiburg, Göttingen and Munich are funded by the Federal Ministry of Education and Research (BMBF). In order to explore the complex structure of the brain, computational neuroscience combines experiment, computer simulation and theory building.
Additional Information:

Dr. Carsten Mehring
Institute for Biology I and Bernstein Center for Computational Neuroscience
Tel .: 0761 / 203-2543
Email: [email protected]

Tobias Pistohl
Institute for Biology I and Bernstein Center for Computational Neuroscience
Tel .: 0761 / 203-2580
Email: [email protected]