Hartwigsen Gesa, Golombek Thomas, Obleser Jonas
Language & Aphasia Laboratory, Department of Neurology, University of Leipzig, Leipzig, Germany; Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; Department of Psychology, Christian-Albrechts-University, Kiel, Germany.
Language & Aphasia Laboratory, Department of Neurology, University of Leipzig, Leipzig, Germany; Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
Cortex. 2015 Jul;68:100-10. doi: 10.1016/j.cortex.2014.08.027. Epub 2014 Sep 18.
Increased neural activity in left angular gyrus (AG) accompanies successful comprehension of acoustically degraded but highly predictable sentences, as previous functional imaging studies have shown. However, it remains unclear whether the left AG is causally relevant for the comprehension of degraded speech. Here, we applied transient virtual lesions to either the left AG or superior parietal lobe (SPL, as a control area) with repetitive transcranial magnetic stimulation (rTMS) while healthy volunteers listened to and repeated sentences with high- versus low-predictable endings and different noise vocoding levels. We expected that rTMS of AG should selectively modulate the predictability gain (i.e., the comprehension benefit from sentences with high-predictable endings) at a medium degradation level. We found that rTMS of AG indeed reduced the predictability gain at a medium degradation level of 4-band noise vocoding (relative to control rTMS of SPL). In contrast, the behavioral perturbation induced by rTMS changed with increased signal quality. Hence, at 8-band noise vocoding, rTMS over AG versus SPL decreased the number of correctly repeated keywords for sentences with low-predictable endings. Together, these results show that the degree of the rTMS interference depended jointly on signal quality and predictability. Our results provide the first causal evidence that the left AG is a critical node for facilitating speech comprehension in challenging listening conditions.
正如先前的功能成像研究所示，左侧角回（AG）神经活动增加伴随着对声学上退化但高度可预测句子的成功理解。然而，左侧角回对于理解退化语音是否具有因果相关性仍不清楚。在此，我们在健康志愿者听并重复具有高可预测性与低可预测性结尾以及不同噪声声码水平的句子时，使用重复经颅磁刺激（rTMS）对左侧角回或顶上叶（SPL，作为对照区域）施加短暂虚拟损伤。我们预期，在中等退化水平下，AG的rTMS应选择性地调节可预测性增益（即，从具有高可预测性结尾的句子中获得的理解益处）。我们发现，在4频段噪声声码的中等退化水平下，AG的rTMS确实降低了可预测性增益（相对于SPL的对照rTMS）。相反，rTMS引起的行为扰动随信号质量的提高而变化。因此，在8频段噪声声码时，与SPL相比，AG上的rTMS减少了具有低可预测性结尾句子的正确重复关键词数量。总之，这些结果表明，rTMS干扰的程度共同取决于信号质量和可预测性。我们的结果提供了首个因果证据，表明左侧角回是在具有挑战性的听力条件下促进言语理解的关键节点。
