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Phosphene

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Microcontroller-gesteuerte Schaltung zur Erzeugung von Phosphenen

Betreuer: Dr.-Ing. Wolfram RoƟdeutscher

Bearbeiter:
Menja Scheer

Purpose: For the acute treatment of migraine there are, until now, several different methods, including transcranial magnetic stimulation (TMS) therapy, which seems to help the patients to better deal with their disease [1]. In the case of TMS the underlying effect is not yet clear. One possible explanation for the observed effects is, that a modification at neuronal level, evoked by the magnetic field, disrupts the cortical spreading depolarization (CSD) wave [2]. This CSD wave is known to cause the neurological symptoms in migraine, the so called aura [3]. To improve the efficacy of the TMS treatment, a better knowledge of the underlying processes is of essential importance. To learn more about these processes is the long term goal of the project containing the given master thesis. To achieve this, we want to examine whether the stimulation-protocol used in current TMS is able to affect perceptual patterns that are similar to those seen during the migraine aura, that is, hallucinatory geometric patterns of cortical origin. If so, this would strongly indicate that these stimulation-protocols are also able to interact with the CSD wave.
Methods: As preparation for a clinical study, following the given master thesis, a literature research is done to gain basic knowledge in the fields belonging to the master thesis. To induce hallucinatory geometric patterns, a microcontroller driven LED device is built to allow the user to test various hypotheses on the influence of TMS on neural activity. This includes the complete layout and building process of a board that allows the user to choose from different flicker frequencies and present them, using self-made LED-glasses to some volunteers. With this LED-Device the existence of different hallucinatory patterns in response to different flicker frequencies is tested as well as the influence of TMS on these observed patterns.
Results: To give the user an easy possibility to choose between several frequencies, a switch was mounted on the board and connected to the microcontroller. Based on the literature and our own tests, we decided to use a flicker frequency range of 3 to 19Hz. To give the user the possibility to evaluate the results, different categories for the observed patterns are determined. As preparation for the study, following the given master thesis, a test procedure, that should fulfill the quality criteria of objectivity, standardization, reliability and validity, is developed and proved with some volunteers. This test procedure includes the exploration of the existence of subjectively different patterns in response to different flicker frequencies and the effect of TMS on these perceived patterns near transition states in regard of their significance for TMS treatment in migraine.
Conclusion: After the Preparation and Pre-tests done in this work a scientific study should follow to be able to give a reliable statement about the influence of TMS on hallucinatory patterns with cortical origin and based on this on migraine. With these results the TMS protocol for migraine therapy could be optimized based on simulations concerning the propagation of the CSD-wave done by the SFB910 at the TU Berlin.


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