Placebo Brain Stimulation Affects Subjective but Not Neurocognitive Measures of Error Processing
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ORIGINAL RESEARCH
Placebo Brain Stimulation Affects Subjective but Not Neurocognitive Measures of Error Processing Michiel van Elk 1,2 & Eva Groenendijk 1 & Suzanne Hoogeveen 1,2 Received: 15 January 2020 / Accepted: 22 April 2020 # The Author(s) 2020
Abstract The aim of this preregistered EEG study was to show how expectations about enhanced or impaired performance through transcranial stimulation affect feelings of agency and error processing. Using a single-blind experimental design, participants (N = 57) were attached to a transcranial direct current stimulation (tDCS) device, and in different blocks, they were verbally instructed to expect enhanced or impaired cognitive performance, or no effects of the brain stimulation. In all cases, but unbeknownst to the participants, we used an inert sham tDCS protocol. Subsequently, we measured their response to errors on a cognitive control task. Our expectancy manipulation was successful: participants reported improved subjective performance in the enhancement compared with the impairment condition—even though objective performance was kept at a constant level across conditions. Participants reported the highest feelings of agency over their task performance in the control condition, and lowest feelings of agency in the impairment condition. The expectancy manipulation did not affect the error-related negativity (ERN) in association with incorrect responses. During the induction phase, expecting impaired versus enhanced performance increased frontal theta power, potentially reflecting a process of increased cognitive control allocation. Our findings show that verbally induced manipulations can affect subjective performance on a cognitive control task, but that stronger manipulations (e.g., through conditioning) are necessary to induce top-down effects on neural error processing. Keywords Neuroenchantment . Brain stimulation . Error-related negativity . Feelings of agency
Introduction The emergence of new technologies, such as self-driving cars or bioengineering, often raises issues regarding personal responsibility. Take for instance the example of a patient suffering from obsessive-compulsive disorder (OCD), who has been treated with the implantation of deep brain electrodes (Figee et al. 2013). The brain stimulation may relieve the patient from OCD-related symptoms, but now suppose that the patient would suddenly be found stealing money from a cash register. Could he blame the deep brain stimulation for his morally inappropriate behavior? Or take the example of a student who is using a commercially available brain * Michiel van Elk [email protected] 1
Department of Psychology, University of Amsterdam, Nieuwe Achtergracht 129B, 1018 XA Amsterdam, The Netherlands
2
Amsterdam Brain and Cognition Center, University of Amsterdam, Amsterdam, The Netherlands
stimulation device for cognitive enhancement. He can attribute improved concentration while studying to the transcranial stimulation, but what would happen when he encounters a negative outcome such as insomnia or
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