School of Psychology, The University of Western Australia, Crawley, WA, Australia.
Eur J Neurosci. 2013 Sep;38(5):2802-11. doi: 10.1111/ejn.12280. Epub 2013 Jun 14.
We report three studies of the effects of anodal transcranial direct current stimulation (tDCS) over auditory cortex on audition in humans. Experiment 1 examined whether tDCS enhances rapid frequency discrimination learning. Human subjects were trained on a frequency discrimination task for 2 days with anodal tDCS applied during the first day with the second day used to assess effects of stimulation on retention. This revealed that tDCS did not affect learning but did degrade frequency discrimination during both days. Follow-up testing 2-3 months after stimulation showed no long-term effects. Following the unexpected results, two additional experiments examined the effects of tDCS on the underlying mechanisms of frequency discrimination, place and temporal coding. Place coding underlies frequency selectivity and was measured using psychophysical tuning curves with broader curves indicating poorer frequency selectivity. Temporal coding is determined by measuring the ability to discriminate sounds with different fine temporal structure. We found that tDCS does not broaden frequency selectivity but instead degraded the ability to discriminate tones with different fine temporal structure. The overall results suggest anodal tDCS applied over auditory cortex degrades frequency discrimination by affecting temporal, but not place, coding mechanisms.
我们报告了三项关于经颅直流电刺激（tDCS）对人类听觉皮层影响的研究。实验 1 检验了阳极 tDCS 是否能增强快速频率辨别学习。人类受试者在两天内接受频率辨别任务的训练，第一天施加阳极 tDCS，第二天用于评估刺激对保留的影响。结果表明，tDCS 不会影响学习，但会在两天内降低频率辨别能力。刺激后 2-3 个月的随访测试显示没有长期影响。在出现意外结果后，另外两项实验研究了 tDCS 对频率辨别基础机制（位置和时间编码）的影响。位置编码是频率选择性的基础，通过使用心理物理调谐曲线进行测量，较宽的曲线表示较差的频率选择性。时间编码由测量辨别具有不同精细时间结构的声音的能力来确定。我们发现，tDCS 不会扩大频率选择性，而是降低了辨别具有不同精细时间结构的音调的能力。总体结果表明，施加在听觉皮层上的阳极 tDCS 通过影响时间而不是位置编码机制降低了频率辨别能力。
