Transcranial Alternating Current Stimulation over Frontal Eye Fields Mimics Attentional Modulation of Visual Processing

Misselhorn et al. (2024) report that bilateral in-phase alpha transcranial alternating current stimulation (tACS) over the frontal eye fields (FEF) increases perceptual variability during a contrast discrimination task, which they interpret as mimicking endogenous attention. In this commentary, we challenge that interpretation on both theoretical and methodological grounds. While the behavioural effect is noteworthy, we argue that the observed changes are more plausibly attributed to a disruption in perceptual stability rather than an enhancement of attentional modulation. Specifically, the use of synchronous alpha tACS across both hemispheres may override the brain's intrinsic, lateralised attentional rhythms, particularly the anti-phase dynamics thought to support spatially selective attention.
Moreover, the task employed lacked key features, such as spatial cueing or competition, typically required to engage endogenous attention. Consequently, the observed effect may not reflect attentional mechanisms. We suggest that future research should employ task-relevant attention paradigms, anti-phase stimulation protocols, and real-time neural tracking to clarify the functional impact of externally imposed rhythms on attentional control. A more detailed commentary expanding on these points is available at: [bioRxiv link]