Brain mechanisms of semantic interference in spoken word production: An anodal transcranial Direct Current Stimulation (atDCS) study

Abstract

When naming pictures, categorically-related compared to unrelated contexts typically slow production. We investigated proposed roles for the left inferior frontal gyrus (LIFG) and posterior middle and superior temporal gyri (pMTG/STG) in mediating this semantic interference effect. In a three-way, cross-over, sham-controlled study, we applied online anodal transcranial Direct Current Stimulation (atDCS) to LIFG or pMTG/STG while 24 participants performed parallel versions of the blocked cyclic naming paradigm. Significant effects of semantic context and cycle, and interactions of context and cycle, were observed on naming latencies in all three stimulation sessions. Additionally, atDCS over left pMTG/STG facilitated naming in related blocks from the second cycle onward, significantly reducing but not eliminating the interference effect. Applying atDCS over left LIFG likewise reduced the magnitude of interference compared to sham stimulation, although the facilitation was limited to the first few cycles of naming. We interpret these results as indicating semantic interference in picture naming reflects contributions of two complementary mechanisms: a relatively short-lived, top-down mechanism to bias selection and a more persistent lexical-level activation mechanism.

Limits to tDCS effects in language: Failures to modulate word production in healthy participants with frontal or temporal tDCS

“…This paradigm has been extensively studied (for a review, see Belke & Stielow, 2013), and positive effects of tDCS have been reported (Meinzer et al., 2016, Pisoni et al., 2012, Wirth et al., 2011). In this paradigm, participants are asked to repeatedly name sets of pictures that are either semantically related or unrelated.…”

“…As predicted, they found increased interference following stimulation of the temporal lobes, but decreased interference following anodal tDCS of the frontal lobe. Meinzer, Yetim, McMahon, and de Zubicaray (2016) and Wirth et al. (2011) also found decreased interference during frontal tDCS with the same paradigm.…”

tDCS modulation of naming in healthy participants: Negative results and still no explanation – A response to a commentary by Gauvin et al. (2017)

“…Exploring the possible modulation of semantic interference effects in picture naming with LIFG stimulation was therefore a necessary aspect of our investigation. In addition, the LIFG has been the focus of a number of previous studies exploring the effects of tDCS on semantic interference, albeit with inconsistent results, as cited in our paper (e.g., Meinzer, Yetim, McMahon, & de Zubicaray, 2016;Pisoni, Papagno, & Cattaneo, 2012;Wirth et al, 2011). Far from being unaware of the current debate regarding the role the LIFG plays in semantic interference, as claimed by Gauvin et al, our hypotheses are clearly formulated in light of this debate.…”

“…Direct replications are a good way to evaluate the reliability/efficacy of protocols, which is why our lab is currently conducting several replications of studies, including Meinzer et al (2016) and Pisoni et al (2012). We are continuing in our efforts to establish the conditions under which tDCS is effective.…”

“…Following this commentary, we will also carry out a replication of Meinzer et al (2016) and Pisoni et al (2012). These two studies have targeted the left temporal regions, yet both find discrepant results.…”