用了小状元记忆头戴多久能见效？

即戴即见效。 文献表明，使用 tDCS 10 min，记忆准确度提升 10% [1]；佩戴 30 min，注意力提升 58% [2]；。使用结束后效应持续 60 ‑ 90 分钟 [3]。

[1] Fregni, F., Boggio, P.S., Nitsche, M., Bermpohl, F., Antal, A., Feredoes, E., Marcolin, M.A., Rigonatti, S.P., Silva, M.T., Paulus, W., et al. (2005). Anodal transcranial direct current stimulation of prefrontal cortex enhances working memory. Exp Brain Res 166, 23-30.
[2] Coffman, B.A., Trumbo, M.C., and Clark, V.P. (2012). Enhancement of object detection with transcranial direct current stimulation is associated with increased attention. BMC Neuroscience 13, 108.
[3] Bikson, M., Paulus, W., Esmaeilpour, Z., Kronberg, G., and Nitsche, M.A. (2019). Mechanisms of Acute and After Effects of Transcranial Direct Current Stimulation. In Practical Guide to Transcranial Direct Current Stimulation: Principles, Procedures and Applications, H. Knotkova, M.A. Nitsche, M. Bikson, and A.J. Woods, eds. (Cham: Springer International Publishing), pp. 81-113.