Using transcranial Direct Current Stimulation (tDCS) to modulate the face inversion effect on the N170 ERP component

Abstract

In the present study, we combined tDCS and EEG to examine the electrophysiological responses to the tDCS-induced effects on the face inversion effect showed in recent studies. A double-blind procedure with a between-subjects design (n=48) was used with the subjects, recruited from the student population, being randomly assigned to either tDCS anodal or sham condition. The tDCS stimulation was delivered over the DLPFC at Fp3 site for 10 min at an intensity of 1.5mA while subjects engaged in an old/new recognition task traditionally used to obtain the inversion effect. The behavioural results generally confirmed previous findings. Critically, the results from the N170 show an effect of tDCS. Specifically, the tDCS procedure was able to modulate the N170 peak component by reducing the inversion effect on the latencies (i.e. less delay between upright and inverted faces) and by increasing the inversion effect on the amplitudes (i.e. larger N170 for inverted vs upright faces). We interpret the results based on the previous literature in regard to the inversion effect on the N170 component.