Investigating large-scale brain dynamics using field potential recordings: Analysis and interpretation

New technologies to record electrical activity from the brain on a massive scale offer tremendous opportunities for discovery. Electrical measurements of large-scale brain dynamics, termed field potentials, are especially important to understanding and treating the human brain. Here, our goal is to provide best practices on how field potential recordings (EEG, MEG, ECoG and LFP) can be analyzed to identify large-scale brain dynamics, and to highlight critical issues and limitations of interpretation in current work. We focus our discussion of analyses around the broad themes of activation, correlation, communication and coding. We provide best-practice recommendations for the analyses and interpretations using a forward model and an inverse model. The forward model describes how field potentials are generated by the activity of populations of neurons. The inverse model describes how to infer the activity of populations of neurons from field potential recordings. A recurring theme is the challenge of understanding how field potentials reflect neuronal population activity given the complexity of the underlying brain systems

Is transcranial alternating current stimulation effective in modulating brain oscillations?

Transcranial alternating current stimulation (tACS) is a promising tool for modulating brain oscillations, as well as a possible/ntherapeutic intervention. However, the lack of conclusive evidence on whether tACS is able to effectively affect cortical/nactivity continues to limit its application. The present study aims to address this issue by exploiting the well-known/ninhibitory alpha rhythm in the posterior parietal cortex during visual perception and attention orientation. Four groups of/nhealthy volunteers were tested with a Gabor patch detection and discrimination task. All participants were tested at the/nbaseline and selective frequencies of tACS, including Sham, 6 Hz, 10 Hz, and 25 Hz. Stimulation at 6 Hz and 10 Hz over the/noccipito-parietal area impaired performance in the detection task compared to the baseline. The lack of a retinotopically/norganised effect and marginal frequency-specificity modulation in the detection task force us to be cautious about the/neffectiveness of tACS in modulating brain oscillations. Therefore, the present study does not provide significant evidence for/ntACS reliably inducing direct modulations of brain oscillations that can influence performance in a visual task