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Petra Ritter

Bernstein Center Berlin,
Bernstein Focus Learning,
Charité Universitätsmedizin Berlin


Combining methods to understand human brain function

Understanding the human brain is a great challenge – it is highly complex and very difficult to access experimentally. Electroencephalography (EEG) and Magnetic Resonance Imaging (MRI) allow scientists to watch the brain at work. However, both of these methods have their limits; each method examines only certain aspects of the brain function. Petra Ritter’s work aims at combining these two techniques so that they complement each other in a reasonable way. Even though both methods have already been used for decades, their simultaneous application is still in its infancy. This is mainly due to technical difficulties: the switching of magnetic fields for MRI measurement interferes with the EEG Signal. These problems must now be overcome.

By means of MRI, scientists examine which brain areas are involved in certain functions, e.g. in the processing of visual and acoustic information. However, the temporal resolution of MRI is very low – the rapid repetitions of electric impulses used by nerve cells to process information cannot be resolved. The temporal resolution of EEG is considerably higher. Electrical voltage changes in the brain are measured by electrodes that are attached to the scalp. Only when many neurons synchronize their electric discharges, their activities add up and can be perceived by EEG. Such rhythmic ‘network oscillations’ reflect specific conditions and functions of the brain.

Petra Ritter combines the two methods in order to use the better spatial resolution of MRI and, at the same time, the better temporal resolution of EEG. By doing so, she was able to show in which brain regions the so-called ‘alpha rhythm’ originates and how this rhythm influences the activation level of that region. When eyes are closed, neurons oscillate in the ‘alpha rhythm’, which is suppressed during visual stimulation.

Petra Ritter studied medicine at the Humboldt University Berlin. She spent a large part of her clinical traineeships and practical year abroad: at the universities UCLA and UCSD in Los Angeles and San Diego, the Mount Sinai School of Medicine in New York and the Harvard Medical School in Boston. She completed her period as ‘Ärztin im Praktikum’ (physician in training) in the neurology department of the Charité and, in 2002, she received her license to practise medicine. In 2004, she completed her doctoral thesis, which she also wrote at the Charité, under the supervision of Arno Villringer. Since 2001, Petra Ritter has been in charge of a study group at the Berlin Neuroimaging Center. In the year 2007 she received the Unesco-L'Oréal Prize for young female scientists with children, which is awarded together with the Christiane Nüsslein-Volhard Foundation.