Long-range and cross-frequency neural modulation of gamma flicker on vigilance decrement

Vigilance decrement is a ubiquitous problem in attention-demanding tasks. Therefore, it is significant to develop neuromodulation methods to mitigate the negative neural effect of vigilance decrement. As one of the non-invasive brain stimulation techniques, visual flicker/rhythmic visual stimulation (RVS) has been proposed to entrain neural oscillations and thereby modulate cognitive processes supported by these brain rhythms, but its effects on vigilance decrement are still unclear. Here, we investigated the effect of gamma flicker on vigilance decrement and its underlying neural mechanism. Thirty participants were recruited to perform a 12-min vigilance task. They were required to discriminate the orientation of lateralized triangle targets with/without 40-Hz RVS background. As a result, it was found that 40-Hz RVS mitigated the decrease in perceptual sensitivity ( A^' ) with time-on-task, a typical adverse effect on behaviors caused by vigilance decrement. Electroencephalography (EEG) results showed that 40-Hz RVS could reduce the significant decline of post-stimulus theta-band inter-trial coherence (ITC) in the prefrontal cortex (PFC) with time-on-task. Regression analysis further revealed that the anterior theta-band ITC was significantly correlated to perceptual sensitivity ( A^' ) in a positive manner. These findings indicated that gamma flicker to the visual cortex had a cross-frequency neuromodulation effect on low-frequency EEG responses over the long-range PFC region. Furthermore, this study provides new insights into the neural effects of 40-Hz RVS, which could impact time-on-task effects on vigilance behaviors and alter the utilization of attentional resources.