Bidirectional neural interfaces
The terms "anodal" and "cathodal" are widely used to describe transcranial direct current stimulation (tDCS) of opposing polarities, often interpreted as excitatory and inhibitory, respectively. However, high-definition tDCS allows for complex electrode configurations that may not be characterized accurately as "anodal" and "cathodal."
To illustrate challenges to data interpretation that may result from unclarity about the neuromodulatory effects of different field orientations, we present two high-definition tDCS experiments in the language domain, with different electrode configurations. We also present the modeled electric fields for a traditional tDCS setup, showing how brain stimulation may far exceed target regions.
More research is warranted on the hypothesized inhibitory or excitatory effects of different electrode configurations. Moreover, conventional bicephalic 1 × 1 configurations using sponges or HD electrodes may not be accurately described by the terms "anodal" and "cathodal" either, as these terms only pertain to the desired effects over an area of interest, but not any other areas affected. Therefore, design and interpretation of (HD-)tDCS and conventional tDCS research studies should not be constrained by the anodal/cathodal dichotomy.
Navigated repetitive transcranial magnetic stimulation in stroke rehabilitation (randomize double-blind sham-controlled study)
The problem of functional localization in the brain is one of the most fundamental in neuroscience. For this problem two opposite ideologies: "modular" versus "holistic" nature of the brain also known as "localism" and "holism" have been discussed for a long time (Flourens 1825; Luria 1967). The debate in favor of one or another ideology still can be traced at all methodological levels - from a cell to a system. In this opinion paper we want to raise a question - what is nowadays meant by mapping of the brain? In addition we want to highlight the necessity of being aware of occasionally occurring discontinuity in the research at different methodological scales.