P 214. Visualization of transcranial magnetic stimulation effects by voltage-sensitive dye imaging

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• 作者：V. Kozyrev ; S. Rekauzke ; U.T. Eysel ; D. Jancke
• 刊名：Clinical Neurophysiology
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：124
• 期：10
• 页码：e166
• 全文大小：37 K

文摘

Transcranial magnetic stimulation (TMS) induces electrical currents in the brain which stimulate the neural tissue. Despite the widespread use of TMS, the neuronal mechanisms of TMS-induced activity are not well understood. Here we introduce a novel method of imaging TMS-evoked activity in vivo in a cortical patch (¡«0.5 cm²) stained by a voltage-sensitive dye (VSD). Molecules of the VSD, presumably bound to neuronal membranes, transduce changes of the membrane potential into an optical signal. This signal, originating from large neuronal populations, is recorded by a video camera at high temporal (5 ms) and spatial (¡«50 mkm) resolution, allowing the measurement of dynamics and spatial spread of a TMS pulse. We used VSD imaging to monitor activity induced in primary visual cortex of anesthetized adult cats by single and repetitive (rTMS) pulses as well as alteration of neuronal function during and beyond the stimulation period. We observed a gradual build-up of ongoing cortical activity in response to each magnetic pulse within 10 Hz rTMS trains. We hypothesize that this indicates the evolution of an excitatory cortical state that may facilitate plastic reorganization of orientation map layout. We compared the dynamics of evoked responses to oriented gratings before and after a protocol of 10 Hz rTMS trains presented during 20-30 min. First, a transient suppression within the rise time of responses, typically referred to as deceleration-acceleration notch in VSD recordings (see Sharon and Grinvald, 2002), was significantly diminished indicating weakened inhibition. Second, responses to non-preferred orientations increased while modulation depth, as a global measure of orientation selectivity, was unaltered. Third, preliminary data showed shifts in the balance of represented orientations within the map. Altogether, these findings imply that TMS-induced cortical reorganization processes are accompanied by increased overall plateau levels of nonspecific activity and reduced intracortical inhibition. Our results demonstrate that combining TMS with VSD imaging allows artifact-free visualization of TMS-induced activity in the animal brain and provides a powerful method to study plasticity of the functional cortical architecture.

The project is funded by the Deutsche Forschungsgemeinschaft, SFB 874.