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Vocal response inhibition is enhanced by anodal tDCS over the right prefrontal cortex


Stopping outright (reactive inhibition) and slowing down (proactive inhibition) are types of response inhibition which have mainly been investigated in the manual effector system. This study compared reactive inhibition across manual and vocal effector systems, examined the effects of excitatory anodal transcranial direct current stimulation (anodal tDCS) over the right prefrontal cortex (right-PFC) and looked at the relationship between reactive and proactive inhibition. We hypothesised (1) that vocal reactive inhibition would be less effective than manual reactive inhibition as evidenced by longer stop signal reaction times; (2) that anodal tDCS would enhance both vocal and manual reactive inhibitions and (3) that proactive and reactive inhibitions would be positively related. We tested 14 participants over two sessions (one session with anodal tDCS and one session with sham stimulation) and applied stimulation protocol in the middle of the session, i.e. only during the second of three phases. We used a stop signal task across two stop conditions: relevant and irrelevant stop conditions in which stopping was required or ignored, respectively. We found that reactive inhibition was faster during and immediately after anodal tDCS relative to sham. We also found that greater level of proactive inhibition enhanced reactive inhibition (indexed by shorter stop signal reaction times). These results support the hypothesis that the right-PFC is part of a core network for reactive inhibition and supports previous contention that proactive inhibition is possibly modulated via preactivating the reactive inhibition network.

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This research was supported by Macquarie University Research Excellence Scholarships (MQRES), National Health and Medical Research Council, Australia (#1003760), and the Australian Research Council (DE130100868).

Author contributions

LCM and PFS designed the experiments, collected and analysed the data. LCM, PFS and BWJ wrote the manuscript.

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Correspondence to Leidy J. Castro-Meneses.

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The authors declare that they have no conflict of interest.

Additional information

Leidy J Castro-Meneses and Paul F. Sowman have contributed equally to this work.


Appendix 1

See Table 1.

Table 1 Go reaction times (go-RTs), stop signal delay (SSD) and stop signal reaction times (SSRTs)

Appendix 2

See Table 2.

Table 2 Non-significant interactions for the 2 × 2 × 3 × 2 ANOVA of go-RTs

Appendix 3

Analyses of Spearman correlations between proactive and reactive inhibition.

See Table 3.

Table 3 Spearman correlations between proactive and reactive inhibition (two-tailed)

Appendix 4

Results for the 2 × 3 × 2 repeated-measures ANOVA for proactive inhibition. This ANOVA was done for the effects of two sessions (session with anodal tDCS and session with sham), three phases (phase-1, phase-2 and phase-3) and two response modalities (manual and vocal). The results showed that session had no effect on proactive inhibition.

See Table 4.

Table 4 2 × 3 × 2 repeated-measures ANOVA for proactive inhibition

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Castro-Meneses, L.J., Johnson, B.W. & Sowman, P.F. Vocal response inhibition is enhanced by anodal tDCS over the right prefrontal cortex. Exp Brain Res 234, 185–195 (2016).

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  • Anodal tDCS
  • Vocal inhibition
  • Stop signal task
  • Response inhibition
  • Reactive inhibition and proactive inhibition