Cognitive impairment has been proposed to be the core feature of
schizophrenia (Sz).
Transcranial direct current stimulation (
tDCS) is a non-invasive form of brain stimulation which can improve cognitive function in healthy participants and in psychiatric patients with cognitive deficits.
tDCS has been shown to improve cognition and
hallucination symptoms in Sz, a disorder also associated with marked sensory processing deficits. Recent findings in healthy controls demonstrate that anodal
tDCS increases auditory deviance detection, as measured by the brain-based event-related potential, mismatch negativity (MMN), which is a putative
biomarker of Sz that has been proposed as a target for treatment of Sz cognition. This pilot study conducted a randomized, double-blind assessment of the effects of pre- and post-
tDCS on MMN-indexed auditory discrimination in 12 Sz patients, moderated by
auditory hallucination (AH) presence, as well as working memory performance. Assessments were conducted in three sessions involving temporal and frontal lobe anodal stimulation (to transiently excite local brain activity), and one control session involving '
sham' stimulation (meaning with the device turned off, i.e., no stimulation). Results demonstrated a trend for pitch MMN amplitude to increase with anodal temporal
tDCS, which was significant in a subgroup of Sz individuals with AHs. Anodal frontal
tDCS significantly increased WM performance on the 2-back task, which was found to positively correlate with MMN-
tDCS effects. The findings contribute to our understanding of
tDCS effects for sensory processing deficits and working memory performance in Sz and may have implications for
psychiatric disorders with sensory deficits.