Transcranial Direct Current Stimulation of the Medial Prefrontal Cortex Has No Specific Effect on Self-referential Processes

Abstract

The processing of self-referential information can be influenced by transcranial magnetic stimulation (TMS). The present randomized controlled study investigated whether similar effects can be elicited through the application of transcranial direct current stimulation (tDCS) regarding the "self-serving bias" (SSB) and the "mnemic neglect effect" (MNE). Seventy-five healthy males (M age = 25; SD = 4.3) were investigated in a betweengroups design with random assignment by applying anodal, cathodal, or sham tDCS to the medial prefrontal cortex (mPFC). After stimulation, the participants judged if 80 personality traits (40 positive, 40 negative) were self-descriptive or not. Finally, the participants had to recall the previously presented adjectives. All three stimulation groups showed the expected SSB and MNE. Still, and contrary to our hypotheses, tDCS revealed neither a significant interaction effect between groups and valence concerning the number of chosen self-referential traits (F (2,72) = 1.36, p = 0.26, η 2 G = 0.02) nor an interaction effect between groups, valence, and self-reference concerning the percentage of recalled words (F (2,71) = 0.69, p = 0.50, η 2 G = 0.01). However, a post hoc inspection of effect sizes revealed that less negative traits were indicated as self-referential in the anodal compared to the cathodal group (ES: −0.59; CI: −1.16 to −0.03). Moreover, the participants showed-regardless of self-reference and type of stimulation-a better recall with tDCS in comparison to sham stimulation. Our results indicate that tDCS of the mPFC in healthy young men has no influence on the SSB and the MNE. However, tDCS seems to improve memory performance.

Self-Referential Processing Effects of Non-invasive Brain Stimulation: A Systematic Review

“…Moreover, Dedoncker et al (2019) found that the reduction in negative self-evaluation was associated with reduced functional connectivity between the DLPFC and the left posterior insula. In contrast, the only study targeting the MPFC found no effect of offline tDCS on positive or negative self-evaluation (Mainz et al, 2020).…”

“…Importantly, three studies found that rTMS or anodal tDCS over the MPFC or the DLPFC also reduced negative self-evaluation (self-criticism), suggesting that activation of the prefrontal neurons could have resulted in an overall dampening of emotional response to V-SRP (De Raedt et al, 2017;Dedoncker et al, 2019;De Pisapia et al, 2019). However, Schäfer and Frings (2019) failed to find an effect of anodal VMPFC with cathodal DLPFC tDCS on neutral Mainz et al (2020) failed to find an effect of anodal MPFC with cathodal parietal cortex tDCS on emotional SRP. Considering the V-SRP studies together, a pattern of functional segregation seems to emerge between the left IPL and the MPFC.…”

Examining the influence of brain stimulation to the medial prefrontal cortex on the self‐reference effect in memory

“…Only recently have researchers started investigating the influence of tDCS on the self-reference effect in memory. Interestingly, these past studies show tDCS does not increase the magnitude of the self-reference effect in memory (Mainz et al, 2020;Martin et al, 2019). It is worth noting however, that this past work has focused on item memory (e.g., Mainz et al, 2020), and thus it is less known the extent that selfreference context memory effects might be influenced under active versus sham stimulation.…”

“…Interestingly, these past studies show tDCS does not increase the magnitude of the self-reference effect in memory (Mainz et al, 2020;Martin et al, 2019). It is worth noting however, that this past work has focused on item memory (e.g., Mainz et al, 2020), and thus it is less known the extent that selfreference context memory effects might be influenced under active versus sham stimulation. Thus, in this investigation we examine the influence of tDCS on self-reference context memory effects.…”

“…Given that past work shows that tDCS can improve memory (Bjekić et al, 2019;Brasil-Neto, 2012;Hsu et al, 2015) and that we chose to stimulate a region known to support context memory for self-referentially processed materials, we predict the magnitude of the self-reference context memory effect to be larger under active compared to sham stimulation. Alternatively, because limited past work has shown that the self-reference effect is not enhanced by tDCS (Mainz et al, 2020;Martin et al, 2019), it is possible that stimulation will not affect the self-reference context memory effect. Either outcome (enhanced self-reference context memory effect; no effect of tDCS on memory) will extend understanding of the effects of tDCS on context memory for self-referentially processed information.…”