Differential effects of tactile high- and low-frequency stimulation on tactile discrimination in human subjects

<p>Abstract</p> <p>Background</p> <p>Long-term potentiation (LTP) and long-term depression (LTD) play important roles in mediating activity-dependent changes in synaptic transmission and are believed to be crucial mechanisms underlying learning and cortical plasticity. In human subjects, however, the lack of adequate input stimuli for the induction of LTP and LTD makes it difficult to study directly the impact of such protocols on behavior.</p> <p>Results</p> <p>Using tactile high- and low-frequency stimulation protocols in humans, we explored the potential of such protocols for the induction of perceptual changes. We delivered tactile high-frequency and low-frequency stimuli (t-HFS, t-LFS) to skin sites of approximately 50 mm²on the tip of the index finger. As assessed by 2-point discrimination, we demonstrate that 20 minutes of t-HFS improved tactile discrimination, while t-LFS impaired performance. T-HFS-effects were stable for at least 24 hours whereas t-LFS-induced changes recovered faster. While t-HFS changes were spatially very specific with no changes on the neighboring fingers, impaired tactile performance after t-LFS was also observed on the right middle-finger. A central finding was that for both t-LFS and t-HFS perceptual changes were dependent on the size of the stimulated skin area. No changes were observed when the stimulated area was very small (< 1 mm²) indicating special requirements for spatial summation.</p> <p>Conclusion</p> <p>Our results demonstrate differential effects of such protocols in a frequency specific manner that might be related to LTP- and LTD-like changes in human subjects.</p

Effects of passive stimulation protocols on perceptual abilities and cortical excitability in human somatosensory system of healthy volunteers and focal hand dystonia patients

In dieser Arbeit wird der Einfluss passiver Stimulationsformen auf Erregbarkeit im somatosensorischen System sowie auf taktile Diskriminationsleistung untersucht. Veränderungen in taktiler Diskrimination induziert durch periphere taktile Stimulation werden durch das dopaminerge sowie cholinerge System moduliert. Die Richtung der Veränderungen ist abhängig von der Stimulationsfrequenz, der Anzahl der taktilen Stimuli, der Stimulationsdauer und dem Stimulationsmuster. Niederfrequente Stimulation führt zu einer Verschlechterung der Diskriminationsleistung, während hochfrequente Stimulation diese verbessert. Veränderungen im Tastsinn werden auch durch prekonditionierende kortikale Stimulation moduliert. Hierbei spielt homeostatische Regulation eine wesentliche Rolle. Periphere taktile Stimulation könnte als neurorehabilitative Maßnahme bei fokaler Handdystonie eingesetzt werden, allerdings bedarf es noch experimenteller Versuche an Patientenpopulationen, um dies zu bestätigen

VDS31-IDEE : das standardisierte Interview zur diagnostischen Einschätzung des Entwicklungsmodus von psychotherapeutischen Patienten ; eine Pilotstudie

Die vorliegende Pilotstudie verfolgt das Ziel ein diagnostisches Instrument, in Form eines Interviews mit zugehörigem Kategoriensystem, zu entwickeln, um eine Feststellung des Entwicklungsmodus, abhängig von der Mentalisierungsfähigkeit in bestimmten Situationen, zu ermöglichen. Das Forschungsdesign basiert auf dem Ansatz der Grounded Theory, Mixed Methods werden eingesetzt. Nach Datenerhebung und Interviewdurchführung finden Vor- und Hauptanalyse statt, um das Kategoriensystem zu entwickeln und zu optimieren. Es resultiert ein Kategoriensystem mit 20 Dimensionen, mit dessen Hilfe die Person dem entsprechenden Modus zugeordnet werden kann. Anschließend werden Reliabilität und Validität des Instruments überprüft

Sustained increase of somatosensory cortex excitability by tactile coactivation studied by paired median nerve stimulation in humans correlates with perceptual gain

Cortical excitability can be reliably assessed by means of paired-pulse stimulation techniques. Recent studies demonstrated particularly for motor and visual cortex that cortical excitability is systematically altered following the induction of learning processes or during the development of pathological symptoms. A recent tactile coactivation protocol developed by Godde and coworkers showed that improvement of tactile performance in humans can be achieved also without training through passive stimulation on a time scale of a few hours. Tactile coactivation evokes plastic changes in somatosensory cortical areas as measured by blood oxygenation level-dependent (BOLD) activation in fMRI or SEP-dipole localization, which correlated with the individual gain in performance. To demonstrate changes in excitability of somatosensory cortex after tactile coactivation, we combined assessment of tactile performance with recordings of paired-pulse SEPs after electrical median nerve stimulation of both the right coactivated and left control hand at ISIs of 30 and 100 ms before, 3 h after and 24 h after tactile coactivation. Amplitudes and latencies of the first and second cortical N20/P25 response components were calculated. For the coactivated hand, we found significantly lowered discrimination thresholds and significantly reduced paired-pulse ratios (second N20/P25 response/first N20/P25 response) at an ISI of 30 ms after tactile coactivation indicating enhanced cortical excitability. No changes in paired-pulse behaviour were observed for ISIs of 100 ms. Both psychophysical and cortical effects recovered to baseline 24 h after tactile coactivation. The individual increase of excitability correlated with the individual gain in discrimination performance. For the left control hand we found no effects of tactile coactivation on paired-pulse behaviour and discrimination threshold. Our results indicate that changes in cortical excitability are modified by tactile coactivation and were scaled with the degree of improvement of the individual perceptual learning. Conceivably, changes of cortical excitability seem to constitute an additional important marker and mechanism underlying plastic reorganization