No Differential Effects of Two Different Alpha-Band Electrical Stimulation Protocols Over Fronto-Parietal Regions on Spatial Attention

Abstract

In a previous study using transcranial alternating current stimulation (tACS), we found preliminary evidence that phase coherence in the alpha band (8–12 Hz) within the fronto-parietal network may critically support top-down control of spatial attention (van Schouwenburg et al., 2017). Specifically, synchronous alpha-band stimulation over the right frontal and parietal cortex (0° relative phase) was associated with changes in performance and fronto-parietal coherence during a spatial attention task as compared to sham stimulation. In the current study, we firstly aimed to replicate these findings with synchronous tACS. Second, we extended our previous protocol by adding a second tACS condition in which the right frontal and parietal cortex were stimulated in a desynchronous fashion (180° relative phase), to test the specificity of the changes observed in our previous study. Participants (n = 23) were tested in three different sessions in which they received either synchronous, desynchronous, or sham stimulation over the right frontal and parietal cortex. In contrast to our previous study, we found no spatially selective effects of stimulation on behavior or coherence in either stimulation protocol compared to sham. We highlight some of the differences in study design that may have contributed to this discrepancy in findings and more generally may determine the effectiveness of tACS.

Individual differences in neuroanatomy and neurophysiology predict effects of transcranial alternating current stimulation

“…The field of tES research has been burdened with variable effects that create replicability problems [1,2,4,5,7,28]. Even meta-analyses of tES effects do not always agree [3,7].…”

Effects of Transcranial Alternating Current Stimulation and Neurofeedback on Alpha (EEG) Dynamics: A Review

“…In spite of many tACS and NFB studies, which have successfully modulated the target EEG activity, there is a potential to find the reports of NFB (Alkoby et al, 2018 ) and tACS participants (van Schouwenburg et al, 2018 ; Manzo et al, 2020 ; Ronconi et al, 2020 ) who showed no response to a particular neuromodulation method. A potential source of variability in response to both modalities has been attributed to different protocol designs, including parameters such as size and montages of electrodes, duration of intervention, and intensity and phase of tACS (Nitsche et al, 2015 ; Karabanov et al, 2016 ; Fertonani and Miniussi, 2017 ; Tavakoli and Yun, 2017 ; Alkoby et al, 2018 ).…”

Frequency-specific transcranial neuromodulation of oscillatory alpha power alters and predicts human visuospatial attention performance

“…Instead, the regression equation takes the data of all participants into account and predicts the stimulation effect at different values of the covariate based on the regression equation (simple slope analysis). This form of analysis could be useful for various brain stimulation studies suffering from variable, weak or inconsistent stimulation effects [62,63,[72][73][74][75][64][65][66][67][68][69][70][71] or studies that want to elaborate on the association between the electrophysiological and the behavioral stimulation effect. Another advantage of mixed model analysis is that the omission of observations due to outlier removal, technical faults or data loss does not lead to exclusion of data on a subject level.…”