Prof. Dr. Klaus Funke, Neurophysiology, Faculty of Medicine

Klaus Funke

Research Programme:

IGSN Students supervised to date: Selcen Aydin-Abidin (admitted Oct 2003).

Recent and ongoing studies of my group are concerned with the cellular effects of transcranial magnetic stimulation (TMS). TMS is a relatively new method to evoke neuronal activity. Briefly, a strong (2-4 tesla), rapidly changing magnetic field is used to induce an electric field inside the brain which is sufficiently strong to elicit action potentials in nearby axons, thereby leading to enhanced synaptic activity within the cortex. By applying single stimuli, TMS can be used to test the excitability of cortical areas or the functionality of nerve tracts, e.g. corticospinal pathways. If applied repetitively, TMS (rTMS) can change cortical excitability in dependence on the repetition frequency. The corresponding cellular mechanisms are largely unknown but are a matter of current clinical and animal studies. Changes in synaptic transmission in terms of synaptic plasticity (long-term potentiation, LTP and depression, LTD) are discussed as a possible mechanism but changes in the activity of remote “modulatory” brain stem systems (dopamine, serotonin, noradrenaline) are also indicated.

Using immunohistochemistry and biochemical methods, we are currently investigating the effect of rTMS on the expression of certain neuronal proteins in rat brain which provide information about recent activation of neurons (e.g. c-fos, zif268) and changes in their synaptic state (calcium-binding proteins, GAD65/67, GAT-1). We could already show that different rTMS protocols (low or high frequency) lead to different changes in protein expression and that distinct neuronal networks are affected. In the near future, we are going to study the effects of different rTMS protocols on learning behavior and memory in rats, combined with further histological investigations of specific markers of synaptic plasticity.