RESUMO
Neuronal plasticity is considered to be the neurophysiological correlate of learning and memory and changes in corticospinal excitability play a key role in the normal development of the central nervous system as well as in developmental disorders. In a previous study, it was shown that quadri-pulse theta burst stimulation (qTBS) can induce bidirectional changes in corticospinal excitability (1). There, a quadruple burst consisted of four single-sine-wave (SSW) pulses with a duration of 160 µs and inter-pulse intervals of 1.5 ms to match I-wave periodicity (666 Hz). In the present study, the pulse shape was modified applying double-sine-waves (DSW) rather than SSW pulses, while keeping the pulse duration at 160 µs. In two separate sessions, we reversed the current direction of the DSW pulse, so that its second component elicited either a mainly posterior-to-anterior (DSW PA-qTBS) or anterior-to-posterior (DSW AP-qTBS) directed current in the precentral gyrus. The after-effects of DSW qTBS on corticospinal excitability were examined in healthy individuals (n = 10) with single SSW TMS pulses. For single-pulse SSW TMS, the second component produced the same preferential current direction as DSW qTBS but had a suprathreshold intensity, thus eliciting motor evoked potentials (PA-MEP or AP-MEP). Single-pulse SSW TMS revealed bidirectional changes in corticospinal excitability after DSW qTBS, which depended on the preferentially induced current direction. DSW PA-qTBS at 666 Hz caused a stable increase in PA-MEP, whereas AP-qTBS at 666 Hz induced a transient decrease in AP-MEP. The sign of excitability following DSW qTBS at I-wave periodicity was opposite to the bidirectional changes after SSW qTBS. The results show that the pulse configuration and induced current direction determine the plasticity-effects of ultra-high frequency SSW and DSW qTBS at I-wave periodicity. These findings may offer new opportunities for short non-invasive brain stimulation protocols that are especially suited for stimulation in children and patients with neurological or neurodevelopmental disorders.
RESUMO
Introduction: One of the most important extracurricular aspects of medical studies in Germany is a research thesis completed by most students. This research project often times conveys relevant competencies for the physician's role as scientist. Nevertheless, the choice of the right project remains a challenge. Reasons for this are among others, missing structures for a comprehensive overview of research groups and their respective projects. Description of the project: We developed the online platform Doktabörse as an online marketplace for doctoral research projects. The platform enables authorized researchers to create working groups and upload, deactivate and change research projects within their institute. For interested students, a front end with integrated search function displays these projects in a structured and well-arranged way. In parallel, the Doktabörse provides for a comprehensive overview of research at the medical faculty. We evaluated Researchers' and students' use of the platform. Results: 96,6% of students participating in the evaluation (n=400) were in favor of a centralized research platform at the medical faculty. The platform grew at a steady pace and included 120 research groups in June 2016. The students appreciated the structure and design of the Doktabörse. Two thirds of all uploaded projects matched successfully with doctoral students via the platform and over 94% of researchers stated that they did not need technical assistance with uploading projects and handling the platform. Discussion: The Doktabörse represents an innovative and well accepted platform for doctoral research projects. The platform is perceived positively by researchers and students alike. However, students criticized limited extent and timeliness of offered projects. In addition, the platform serves as databank of research at the medical faculty of the LMU Munich. The future potential of this platform is to provide for an integrated management solution of doctoral thesis projects, possibly beyond the medical field and faculty.