sham
sham relates to brain function and cognitive performance. Peak Brain Institute explores how QEEG brain mapping and neurofeedback training connect to sham through evidence-based approaches. Explore our 2 research papers covering this topic.
Research Papers
Electrodermal Activity Biofeedback Alters Evolving Functional Brain Networks in People With Epilepsy, but in a Non-specific Manner
There is evidence that biofeedback of electrodermal activity (EDA) can reduce seizure frequency in people with epilepsy. Prior studies have linked EDA biofeedback to a diffuse brain activation as a potential functional mechanism. Here, we investigated whether short-term EDA biofeedback alters EEG-derived large-scale functional brain networks in people with epilepsy. In this prospective controlled trial, thirty participants were quasi-randomly assigned to one of three biofeedback conditions (arousal, sham, or relaxation) and performed a single, 30-min biofeedback training while undergoing continuous EEG recordings. Based on the EEG, we derived evolving functional brain networks and examined their topological, robustness, and stability properties over time. Potential effects on attentional-executive functions and mood were monitored via a neuropsychological assessment and subjective self-ratings. Participants assigned to the relaxation group seemed to be most successful in meeting the task requirements for this specific control condition (i.e., decreasing EDA). Participants in the sham group were more successful in increasing EDA than participants in the arousal group. However, only the arousal biofeedback training was associated with a prolonged robustness-enhancing effect on networks. Effects on other network properties were mostly unspecific for the different groups. None of the biofeedback conditions affected attentional-executive functions or subjective behavioral measures. Our results suggest that global characteristics of evolving functional brain networks are modified by EDA biofeedback. Some alterations persisted after the single training session; however, the effects were largely unspecific across the different biofeedback protocols. Further research should address changes of local network characteristics and whether multiple training sessions will result in more specific network modifications.
View Full Paper →Toward Development of Sham Protocols for High-Definition Transcranial Direct Current Stimulation (HD-tDCS)
High-definition transcranial direct current stimulation (HD-tDCS) is a noninvasive cortical stimulation (NICS) technique that, due to the utilization of multi-electrode stimulation, may enable development of sham conditions characterized by indistinguishable scalp sensations compared to active conditions, with little or no cortical influence. We sought to contribute to the development of an optimal sham electrode configuration for HD-tDCS protocols by gathering ratings of overall sensation reported by participants during different electrode configurations and current intensities. Twenty healthy participants completed a magnitude estimation task during which they rated their “overall sensation” in 1-minute intervals during five 5-minute stimulation conditions. A 5 x 5 (Time x Stimulation condition) analysis of variance (ANOVA) was conducted to determine if sensation measurements differed over time, and how this varied by condition. Null hypothesis significance tests and equivalence tests were conducted to determine which sham conditions were statistically indistinguishable from the experimental condition. The ANOVA revealed main effects for Time and Stimulation condition. Planned comparisons, comparing each sham condition to the experimental condition (4x1 ring configuration, 2 mA), revealed differences in sensation ratings for all but one condition (Sham 1x1A); no sham conditions were found to be statistically equivalent to the experimental condition. Our HD-tDCS findings build upon previous NICS reports of differences in sensation ratings between sham versus experimental conditions when traditional “ramping down” approaches were used. Alternative multi-electrode configurations that manipulate electrode placement to shunt current across the scalp warrant further investigation as valid blinding methods.
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