Static outcomes: Anodal transcranial direct current stimulation at Fp3 or P3 does not modulate perceptual learning as indexed by the intermixed-blocked effect.

Perceptual learning can be defined as a relatively permanent change in discrimination performance as a result of experience or exposure. One key index of perceptual learning is the intermixed-blocked effect in which exposure to two ambiguous or perceptually similar stimuli (i.e., AX and BX) exposed in an intermixed fashion (AX, BX, AX, BX, AX, BX) produces enhanced discrimination performance compared with blocked exposure (AX, AX, AX, BX, BX, BX). Previous imaging data have implicated multiple brain regions in the intermixed-blocked effect. In the present study, transcranial direct current stimulation was used to explore the causal relationship of two regions, the dorsolateral prefrontal cortex (DLPFC) and the posterior parietal cortex (PPC), to performance. A mixed, double-blind, design administered two online sessions of transcranial direct current stimulation (active and sham) to 48 participants, although they viewed pairs of similar stimuli. Half of the participants received active stimulation to the DLPFC, and the other half to the PPC. Anodal stimulation in either the DLPFC or the PPC provided no modulation of discrimination performance relative to sham stimulation. These results potentially question the generality of the interpretation of other studies in which stimulation of these areas does impact on other indices of perceptual learning. (PsycInfo Database Record (c) 2026 APA, all rights reserved).