Abstract
There has been increasing interest in the utility of transcranial electrical stimulation as a tool to enhance cognitive abilities. In the domain of face perception, enhancements have been reported for both transcranial direct current stimulation (tDCS) and high-frequency transcranial random noise stimulation (tRNS) targeting the occipitotemporal cortex. In a series of two experiments, we attempted to replicate these findings for face identity perception, and extend on previous studies, to determine if similar enhancements are also observed for object and facial expression perception. In Experiment 1, using a single blind, between-subjects design in healthy volunteers (N = 53), we examined whether anodal tDCS over the occipitotemporal cortex enhanced performance on tasks involving perception of face identity, facial expression, and object stimuli, when compared to sham stimulation. We failed to replicate previous findings of enhanced performance on face and object perception, nor extend findings to facial expression perception. In Experiment 2, using a single blind, between-subjects design (N = 39), we examined the effect of high-frequency tRNS over the occipitotemporal cortex using the same three tasks employed in Experiment 1. We failed to replicate previous findings of enhanced face perception following high-frequency tRNS over the occipitotemporal cortex, relative to sham stimulation (although we used different stimulation parameters to that employed in a previous study). We also found no evidence of enhanced facial expression and object perception following high-frequency tRNS. The findings align with a growing body of studies that have failed to replicate previously reported enhancements following administration of tDCS and hint for different efficacy of, on first sight, related stimulation protocols. Future studies should explore the foundation of these differential effects in greater detail.
Highlights
There has been a surge of research interest concerning individuals who experience difficulties in face recognition
We sought to determine if such enhancement extended to object and facial expression perception
In Experiment 1, we found no evidence of enhanced face perception following anodal transcranial direct current stimulation (tDCS) targeting the right occipitotemporal cortex
Summary
There has been a surge of research interest concerning individuals who experience difficulties in face recognition (for reviews, see Rivolta et al, 2013; Corrow et al, 2016). Face recognition difficulties have been observed in clinical populations who experience a range of social cognitive difficulties, including individuals with conditions such as autism spectrum disorder (e.g., Tang et al, 2015), and schizophrenia (e.g., Green et al, 2015). One transcranial electrical stimulation technique, which has received the most research interest to date, is transcranial direct current stimulation (tDCS). The widespread assumption is that tDCS exerts its effects by modulating cortical excitability via subthreshold depolarization or hyperpolarization of resting membrane potentials, with anodal stimulation inducing excitatory effects via depolarization, and cathodal stimulation exerting inhibitory effects via hyperpolarization (Nitsche et al, 2008). The extent to which these changes in cortical excitability transfer to enhanced cognitive performance (following anodal stimulation) and diminished cognitive performance (following cathodal stimulation) is far from conclusive, with a notable lack of evidence to support the assertion that cathodal stimulation diminishes cognitive performance (e.g., Jacobson et al, 2012; Costantino et al, 2017)
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