Cathodal tDCS increases stop-signal reaction time

Abstract

Transcranial direct current stimulation (tDCS) is a noninvasive method of modulating human brain activity and potentially alters performance in cognitive tasks. Often it is assumed that effects of tDCS modulation depend on the polarity-anodal stimulation typically boost cognitive processes whereas cathodal stimulation hampers them. While most tDCS research focusses on the effects of anodal stimulation, cathodal tDCS effects are underexplored. In the present study, cathodal tDCS over the right dorsolateral prefrontal cortex (rDLPFC) was used to potentially hamper the response inhibition process as measured by the stop-signal task (SST). A 9 cm 2 cathode was always positioned over the rDLPFC while the 35 cm 2 anode was placed over the left deltoid. We contrasted a cathodal stimulation condition (that is assumed to reduce neural processing) with sham stimulation and expected a decrease in SST performance after cathodal tDCS, as evidenced by an increase in stop-signal reaction time (SSRT). In a sample of N = 45 healthy adults, a significant Time × tDCS condition interaction emerged, indicating an increase in SSRT after cathodal tDCS. In a recent study by Friehs and Frings (Journal of Experimental Psychology: Human Perception and Performance, 2018), using a similar study design and stimulation protocol, single-session anodal tDCS over the rDLPFC was used to enhance SST performance as indicated by an acceleration of SSRT. In concert, these results suggest that response inhibition is tied to the neural state of the rDLPFC.

Regional specificity of cathodal transcranial direct current stimulation (tDCS) effects on spatial‐numerical associations: Comparison of four stimulation sites

“…Third, in the stop‐signal task, cathodal tDCS to the right PFC had moderate–strong effect size of Cohen's d = 0.70 (Friehs & Frings, ). Note that the two other cathodal tDCS studies with stop‐signal task used a cortical return anode (Jacobson et al, ; Stramaccia et al, ), but Friehs and Frings () electrode configuration comes closest to our study despite a pure offline design.…”

“…Participants who receive sham stimulation will be later collapsed to a single‐sham tDCS group ( n = 32) since different sham configurations are not expected to produce differential effects. The return electrode (anode) is placed extracranially on the contralateral upper arm (M. deltoideus) to avoid an opposite polarization in another brain area and thus ensure that tDCS effects can be traced back exclusively to stimulation of the target region (Friehs & Frings, ; Schroeder et al, ). For the online assessment, both tasks are performed concurrent to active tDCS.…”

“…To date, various brain stimulation studies have already confirmed a causal link between response inhibition and the right PFC using transcranial magnetic stimulation (Chambers et al, ) or tDCS (Friehs & Frings, ; Hogeveen et al, ; Jacobson et al, ; Nieratschker et al, ). Regional specificity of response inhibition in the stop‐signal task was already investigated with excitability‐enhancing anodal tDCS in previous studies, which led to improved response inhibition (Hogeveen et al, ; Jacobson et al, ; Stramaccia et al, ).…”

“…When using transcranial direct current stimulation (tDCS), a weak direct current is sent through the scalp which would slightly depolarize or hyperpolarize most resting membrane thresholds in a targeted region, mostly dependent on electrode position and current direction (Fertonani & Miniussi, ; Nitsche & Paulus, ; Priori, Berardelli, Rona, Accornero, & Manfredi, ). Accordingly, in neurocognitive investigations, hyperpolarizing cathodal tDCS to prefrontal regions can modulate certain cognitive processes, for example, to impair working memory processes (Wolkenstein, Zeiller, Kanske, & Plewnia, ; Zaehle, Sandmann, Thorne, Jäncke, & Herrmann, ) and reduce implicit associations (Schroeder, Nuerk, & Plewnia, ; Schroeder, Pfister, Kunde, Nuerk, & Plewnia, ) or response inhibition (Friehs & Frings, ; Hogeveen et al, ; Jacobson, Javitt, & Lavidor, ; Nieratschker, Kiefer, Giel, Krüger, & Plewnia, ). Thereby, this technology allows not only for a modulation of cognitive processing, but can also provide a critical test for a theory that predicts united or divided systems which should respond to regional brain stimulation in ensemble or produce dissociable modulations, respectively.…”

“…Regional specificity of response inhibition in the stop‐signal task was already investigated with excitability‐enhancing anodal tDCS in previous studies, which led to improved response inhibition (Hogeveen et al, ; Jacobson et al, ; Stramaccia et al, ). The present confirmatory research will utilize cathodal tDCS, which led to impaired response inhibition when administered over right PFC (Friehs & Frings, ). Moreover, by collecting data from the stop‐signal task next to the magnitude comparison task in one large study design, we expect to empirically outline the task‐selectivity of regional tDCS configurations.…”