Anodal-tDCS over the human right occipital cortex enhances the perception and memory of both faces and objects

Accurate face processing skills are pivotal for typical social cognition, and impairments in
this ability characterise various clinical conditions (e.g., prosopagnosia). No study to date has
investigated whether transcranial direct current stimulation (tDCS) can causally enhance face
processing. In addition, the category- and the process- specificity of tDCS effects, as well as
the role of the timing of neuromodulation with respect to the execution of cognitive tasks are
still unknown. In this single-blind, sham-controlled study, we examined whether the
administration of anodal-tDCS (a-tDCS) over the right occipital cortex of healthy volunteers
(N = 64) enhances performance on perceptual and memory tasks involving both face and
object stimuli. Neuromodulation was delivered in two conditions: online (a-tDCS during task
execution) and offline (a-tDCS before task execution). The results demonstrate that offline atDCS
enhances the perception and memory performance of both faces and objects. There was
no effect of online a-tDCS on behaviour. Furthermore, the offline effect was site-specific
since a-tDCS over the sensory-motor cortex did not lead to behavioural changes. Our results
add relevant information about the breadth of cognitive processes and visual stimuli that can
be modulated by tDCS, and about the design of effective neuromodulation protocols, which
have implications for advancing theories in cognitive neuroscience and clinical applications.