Effects of transcranial alternating current stimulation over right-DLPFC on vigilance tasks depend on the arousal level

Abstract

Current theoretical accounts on the oscillatory nature of sustained attention predict that entrainment via transcranial alternating current stimulation (tACS) at alpha and theta frequencies on specific areas of the prefrontal cortex could prevent the drops in vigilance across time-on-task. Nonetheless, most previous studies have neglected both the fact that vigilance comprises two dissociable components (i.e., arousal and executive vigilance) and the potential role of differences in arousal levels. We examined the effects of theta- and alpha-tACS over the right dorsolateral prefrontal cortex in both components of vigilance and in participants who differed in arousal level according to their chronotype and time of testing. Intermediate-types performed the vigilance tasks when their arousal level was optimal, whereas evening-types performed the vigilance tasks when their arousal levels were non-optimal. Both theta- and alpha-tACS improved arousal vigilance in the psychomotor vigilance task (PVT), whereas alpha-tACS, but not theta-tACS, improved executive vigilance in the sustained attention to response task (SART), and counteracted the typical vigilance decrement usually observed in this task. Importantly, these stimulation effects were only found when arousal was low (i.e., with evening-types performing the tasks at their non-optimal time of day). The results support the multicomponent view of vigilance, the relevance of heeding individual differences in arousal, and the role of alpha oscillations as a long-range cortical scale synchronization mechanism that compensates the decrements in performance as a function of time-on-task by exerting and maintaining cognitive control attributed to activation of the right dorsolateral prefrontal cortex.

Circadian Modulation of the Time Course of Automatic and Controlled Semantic Processing

“…The main effect of time-of-day was statistically signi cant, F(1, 38) = 5.61; p = .02; η p 2 = .13, which indicated that, in general, performance at the optimal time produced shorter RTs (319 ms) than at the non-optimal time (341 ms). The difference in performance between the optimal and non-optimal time-ofday according to the different chronotypes is referred to as the synchrony effect and the current results replicate those obtained in other experiments using the same task (11,35,40). Accordingly, the current synchrony effect con rms the appropriate selection of our sample of extreme chronotypes.…”

“…To ensure the appropriate selection of our sample of extreme chronotypes, we used the psychomotor vigilance task (PVT). This task has been shown to be very sensitive to circadian-related performance (34) and has been widely used in cognitive research (11,12,35,36). To assess the effects of chronotype and time of testing on automatic processing, we explored facilitatory priming with a short prime-target SOA (100 ms).…”

The neuroelectrophysiological and behavioral effects of transcranial direct current stimulation on executive vigilance under a continuous monotonous condition

“…Second, tDCS was conducted in the offline mode before cognitive fatigue occurred. Both groups were at a good arousal level and emotional state before tDCS, resulting in no significant enhancement of tDCS in a state-dependent manner (Martínez-Pérez et al, 2022).…”

“…This may be related to participants’ basal state. A study showed that transcranial alternating current stimulation (tACS) at alpha frequency improved executive vigilance in the SART only when arousal was low ( Martínez-Pérez et al, 2022 ). In this study, both groups were at a good arousal level and emotional state before tDCS (see Table 1 ).…”

“…Second, tDCS was conducted in the offline mode before cognitive fatigue occurred. Both groups were at a good arousal level and emotional state before tDCS, resulting in no significant enhancement of tDCS in a state-dependent manner ( Martínez-Pérez et al, 2022 ). Third, the vigilance task adopted in this study is a simple and monotonous sustained attention task which not consume too many mental resources.…”