“Unfocus” on foc.us: commercial tDCS headset impairs working memory

Abstract

An Editorial Expression of Concern to this article was published on 13 July 2022

The Editors-in-Chief are issuing an editorial Expression of Concern for this article. An investigation by Universiteit Leiden has concluded that in the reporting of this study data from at least two participants were omitted or replaced without this being disclosed. However, the investigation was unable to determine the exact number of participants whose data were omitted or replaced. The first/corresponding author has stated that data from five participants were excluded prior to analysis due to poor task performance without this being disclosed. Readers should therefore interpret the results and conclusions with caution. All authors agree with this statement.

In this study, we tested whether the commercial transcranial direct current stimulation (tDCS) headset foc.us improves cognitive performance, as advertised in the media. A single-blind, sham-controlled, within-subject design was used to assess the effect of online and off-line foc.us tDCS—applied over the prefrontal cortex in healthy young volunteers (n = 24) on working memory (WM) updating and monitoring. WM updating and monitoring, as assessed by means of the N-back task, is a cognitive-control process that has been shown to benefit from interventions with CE-certified tDCS devices. For both online and off-line stimulation protocols, results showed that active stimulation with foc.us, compared to sham stimulation, significantly decreased accuracy performance in a well-established task tapping WM updating and monitoring. These results provide evidence for the important role of the scientific community in validating and testing far-reaching claims made by the brain training industry.