P79. Facilitative effects of inhibitory stimulation: Number-space associations in the prefrontal cortex. Issue 8 (August 2015) - Schroeder, P.A.
Abstract Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that allows for transient shifts of neural activity. Excitatory, anodal stimulation is believed to be beneficial for cognitive task performance, i.e. WM performance, cognitive control and planning ability. Inhibitory, cathodal stimulation in contrast is believed to decrease neural activity and should thereby result in a decrease of task performance. In the cognitive system, however, this dichotomy is controversial: Besides several null-results that might arise due to complementary activation, even opposed, facilitative effects of cathodal tDCS on task performance have been reported. Here, implicit associations of numbers with space (SNARC effect) are contrasted with explicit location-based associations of laterally shifted targets (Simon effect) in relation to a magnitude and position-irrelevant task (parity and colour judgment, respectively). Cathodal, inhibitory stimulation of the dorsolateral prefrontal cortex, which has been demonstrated to reduce WM capability, dissociated the SNARC effect from the Simon effect and thereby provides evidence for a WM account of spatial–numerical associations. Further, the effect was driven by faster responses to incongruent targets only, revealing the deflective character of number-space associations in parity judgment. Implications for the possible working mechanisms and applications of cathodal tDCS in the cognitive system are discussed.