Department of Psychology, University of Lübeck, Lübeck, Germany.
Experimental Psychology Lab, Center for Excellence "Hearing4all", European Medical School, University of Oldenburg, Oldenburg, Germany.
Brain Stimul. 2018 Jul-Aug;11(4):752-758. doi: 10.1016/j.brs.2018.04.006. Epub 2018 Apr 6.
Spatial attention relatively increases the power of neural 10-Hz alpha oscillations in the hemisphere ipsilateral to attention, and decreases alpha power in the contralateral hemisphere. For gamma oscillations (>40 Hz), the opposite effect has been observed. The functional roles of lateralised oscillations for attention are currently unclear.
If lateralised oscillations are functionally relevant for attention, transcranial stimulation of alpha versus gamma oscillations in one hemisphere should differentially modulate the accuracy of spatial attention to the ipsi-versus contralateral side.
20 human participants performed a dichotic listening task under continuous transcranial alternating current stimulation (tACS, vs sham) at alpha (10 Hz) or gamma (47 Hz) frequency. On each trial, participants attended to four spoken numbers on the left or right ear, while ignoring numbers on the other ear. In order to stimulate a left temporo-parietal cortex region, which is known to show marked modulations of alpha power during auditory spatial attention, tACS (1 mA peak-to-peak amplitude) was applied at electrode positions TP7 and FC5 over the left hemisphere.
As predicted, unihemispheric alpha-tACS relatively decreased the recall of targets contralateral to stimulation, but increased recall of ipsilateral targets. Importantly, this spatial pattern of results was reversed for gamma-tACS.
Results provide a proof of concept that transcranially stimulated oscillations can enhance spatial attention and facilitate attentional selection of speech. Furthermore, opposite effects of alpha versus gamma stimulation support the view that states of high alpha are incommensurate with active neural processing as reflected by states of high gamma.
空间注意力相对增加了与注意力同侧半球的 10Hz 神经α振荡的功率，而降低了对侧半球的α功率。对于γ振荡（>40Hz），则观察到相反的效果。对于注意，侧向振荡的功能作用目前尚不清楚。
如果侧向振荡对于注意力具有功能相关性，那么在一个半球中经颅刺激α与γ振荡应该会以不同的方式调节对同侧和对侧的空间注意力的准确性。
20 名人类参与者在连续经颅交流电刺激（tACS，与假刺激相比）下进行双听任务，刺激频率为α（10Hz）或γ（47Hz）。在每次试验中，参与者专注于左或右耳的四个说话数字，同时忽略另一只耳朵的数字。为了刺激已知在听觉空间注意力期间表现出明显α功率调制的左颞顶皮层区域，在左半球的电极位置 TP7 和 FC5 上施加 tACS（1mA 峰峰值幅度）。
正如所预测的那样，单侧α-tACS 相对降低了对刺激对侧的目标的回忆，但增加了对同侧目标的回忆。重要的是，γ-tACS 的结果呈现出相反的空间模式。
结果提供了一个概念验证，即经颅刺激的振荡可以增强空间注意力，并促进言语的注意力选择。此外，α与γ刺激的相反效果支持了这样的观点，即高α状态与高γ状态下反映的主动神经处理状态不一致。
