Personalized transcranial alternating current stimulation targeting the dorsal attention network specifically modulates visuo-spatial attention

Abstract During intentional shifts of visuo-spatial attention, transcranial alternating current stimulation (tACS) in the alpha frequency range has been shown to modulate attention. A proposed effector of this phenomenon is the modulation of neural alpha power over posterior regions of the dorsal frontoparietal attention network. However, tACS-applications during visuo-spatial attention studies show limited replicability and small effect sizes, which is at least partly explained by individual brain anatomy and thus to differences in electric fields induced by tACS. In the present study, personalized tACS was applied to account for anatomical and functional variability across subjects. Individual sources of neural alpha activity were localised in left and right parietal cortex based on electroencephalography (EEG) data, recorded during a visuo-spatial attention task. Individual finite-element headmodels were computed based on T1- and T2-weighted magnetic resonance imaging data. To evaluate tACS effects, behavioral data and EEG after-effects were assessed in conjunction with individual finite-element simulations of tACS-induced electric fields. First, we found that tACS modulated attention only when targeting the left but not right parietal cortex. As electric field simulations were symmetric in left and right parietal cortices, behavioral effects indicate a functional asymmetry of the dorsal attention network during tACS. Second, we found that neural sources of stimulus-evoked activity localized in left premotor cortex were modulated by tACS. Interestingly, correlations of behavior and simulated electric field intensities suggest a critical role of left premotor regions for tACS-effects on visuo-spatial attention. In sum, results suggest an increased susceptibility of the left parietal and premotor cortex, and thus the left dorsal attention network, to subtle neuromodulation by tACS. Research Category and Technology and Methods Basic Research: 8. Transcranial Alternating Current Stimulation (tACS) Keywords: Personalized tACS, Visuo-spatial attention, Dorsal attention network, Alpha power