Introduction: Neuroplasticity is the adaptive modification of network connectivity in response to environmental demands and has been identified as a major physiological correlate of learning. Since unrestricted neuroplastic modifications of network connectivity will result in a destabilization of the system, metaplastic modification rules have been proposed for keeping plastic connectivity changes within a useful dynamic range. In this connection, the modification threshold to achieve synaptic strengthening is thought to correlate negatively with the history of activity of the respective neurons, i.e. high previous activity enhances the threshold for synaptic strengthening and vice versa. In accordance, it has been shown for the human motor cortex electrophysiologically that excitability-enhancing stimulation with transcranial direct current stimulation (tDCS) caused a subsequent repetitive magnetic stimulation (rTMS) protocol to reduce excitability, while excitability-diminishing tDCS induced reversed effects. However, the relevance of metaplasticity for actual learning processes has not been tested so far.