Enhancing visual perceptual learning using transcranial electrical stimulation: transcranial alternating current stimulation outperforms both transcranial direct current and random noise stimulation

Diverse strategies can be employed to enhance visual skills, including visual perceptual learning (VPL) and transcranial electrical stimulation (tES). Combining VPL and tES is a popular method that holds promise for significant improvements in visual acuity within a short time frame. However, there is still a lack of comprehensive evaluation regarding the effects of combining different types of tES and VPL on enhancing visual function, especially with a larger sample size. In the present study, we recruited four groups of subjects (26 subjects each) to learn an orientation discrimination task with five daily training sessions. During training, subjects occipital region was stimulated by one type of tES (anodal transcranial direct current stimulation (tDCS), alternating current stimulation (tACS) at 10 Hz, high-frequency random noise stimulation (tRNS), and sham tACS) while performing the training task. We found that compared with the sham stimulation, both the high-frequency tRNS and the 10 Hz tACS facilitated VPL efficiently in terms of learning rate and performance improvement, while there was little modulatory effect in the anodal tDCS condition. Remarkably, the 10 Hz tACS condition exhibited superior modulatory effects to the tRNS condition, demonstrating the strongest modulation among the most commonly used tES types for further enhancing vision when combined with VPL. Our results suggest that alpha oscillations play a vital role in VPL. Our study provides a practical guide for vision rehabilitation.