Nov 5, 2018

The Time Course of Ineffective Sham Blinding During 1mA tDCS

BioRxiv : the Preprint Server for Biology
Robert GreinacherGemma Learmonth


Background: Studies using transcranial direct current stimulation (tDCS) typically compare the effects of an active (10-30min) relative to a shorter sham (placebo) protocol. Both active and sham tDCS are presumed to be perceptually identical on the scalp, and thus represent an effective method of delivering double-blinded experimental designs. However, participants often show above-chance accuracy when asked which condition involved active/sham retrospectively. Objective/Hypothesis: We aimed to assess the time course of sham-blinding during active and sham tDCS. We predicted that 1) Participants will be aware that the current is switched on for a longer duration in the active versus the sham protocol, 2) Active anodal tDCS will reduce reaction times more effectively than sham. Methods: 32 adults were tested in a pre-registered, double-blinded, within-subjects design. A forced-choice reaction time task was undertaken before, during and after active (10min 1mA) and sham (20s 1mA) tDCS. The anode was placed over the left primary motor cortex (C3) to target the right hand, and the cathode on the right forehead. Two probe questions were asked every 30s: 'Is the stimulation on?' and 'How sure are you?'. Results: Distinct periods of n...Continue Reading

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Mentioned in this Paper

Left Primary Motor Cortex
Salicylhydroxamic acid
Entire Scalp
Scalp Structure
ZMYM2 wt Allele

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