Biomedical subjects
Publications and source records attributed to F Kohl.
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Nowadays B. v. Gudden is primary known as psychiatrist of the dream-king Ludwig II.; nevertheless he was not only a doctor of the top people, but one of the great clinicians, neuropathologists and psychiatric teachers in the last third of the 19th century. Trained at Siegburg and Illenau, the leading institutions of german mental hospital psychiatry, he was formed by Conolly's "no-restraint"-movement as well as by Griesingers neuropathological concepts. So he became one of the most influential academic teachers of german psychiatry, who attracted important pupils like August Forel or Emil Kraepelin.
In this history of psychiatric therapy the progressive paralysis deserves special interest: for the first time an organic psychosis was treatable successfully by a procedure found by scientific methods. This article describes life and work of Julius Wagner, Ritter von Jauregg (1857-1940) and remembers the introduction of the malaria-therapy, which was developed by Wagner 75 years ago.
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A thin-film multiple-electrode probe for measuring de potentials at eight sites with interdistances of 1 mm was constructed for the investigation of slow potential changes in deep regions of the human brain during surgery. The thin-film electrodes had to be placed on curved cylinder-shaped surgical instruments with dimensions of 2 mm diameter and 33 cm length used with the Freiburg stereotactic equipment. Several novel technological steps had to be introduced for the solution of the encountered problems: 1) Structuring of the metal layers on curved substrates was accomplished by using flexible masks. 2) Special feed-through technologies had to be invented in order to obtain reliable connections between the thin-film sensors and the copper wires inside the stereotactic instrument. 3) Thin-film Ag-AgCl electrodes had to be formed in order to obtain satisfying recordings of slow potential changes below 10 Hz. Slow potential changes were recorded from different depths in interdistances of only 1 mm with these new miniaturized thin film Ag-AgCl electrodes and bipolar recordings with an electrode interdistance of only 3 mm showed clearly the appearance of Bereitschaftspotentials.
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A temperature sensor array was designed in order to study local temperature variations and temperature gradients in biological samples. The sensor probe was inserted in the optical cortex of rabbits in order to study temperature changes during normal brain activity as well as under artificial ventilation conditions. Temperature sensitive areas of 0.14 mm x 0.1 mm are arranged in a row with interdistances of 0.4 mm yielding high spatial resolution. A temperature resolution of 0.1 mK and a 90% response time of maximum 3 milliseconds was obtained utilizing the high temperature dependence of 2%/K of the conductivity of vacuum evaporated germanium films. The sensor is passivated by a 1 micron thick PECVD-silicon nitride layer and can be placed on glass-, alumina- and polymer substrates. For brain tissue studies, in order to minimize tissue damage the temperature sensors were placed on a 0.1 mm thick needle-shaped glass substrate. A sensor element mounted on a glass substrate and immersed in water showed a self heating of less than 5 mK due to the applied measurement current of 2.1 microA.
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