Lise-Meitner Research Group Cognition and Plasticity, Max-Planck-Institute for Human Cognitive and Brain Science, Leipzig, Germany.
School of Psychology, University College Dublin, Dublin, Ireland.
Exp Brain Res. 2023 Jan;241(1):59-66. doi: 10.1007/s00221-022-06505-5. Epub 2022 Nov 10.
Processing ambiguous situations is a constant challenge in everyday life and sensory input from different modalities needs to be integrated to form a coherent mental representation on the environment. The bouncing/streaming illusion can be studied to provide insights into the ambiguous perception and processing of multi-modal environments. In short, the likelihood of reporting bouncing rather than streaming impressions increases when a sound coincides with the moment of overlap between two moving disks. Neuroimaging studies revealed that the right posterior parietal cortex is crucial in cross-modal integration and is active during the bouncing/streaming illusion. Consequently, in the present study, we used transcranial direct current stimulation to stimulate this brain area. In the active stimulation conditions, a 9 cm electrode was positioned over the P4-EEG position and the 35 cm reference positioned over the left upper arm. The stimulation lasted 15 min. Each participant did the bouncing/streaming task three times: before, during and after anodal or sham stimulation. In a sample of N = 60 healthy, young adults, we found no influence of anodal tDCS. Bayesian analysis showed strong evidence against tDCS effects. There are two possible explanations for the finding that anodal tDCS over perceptual areas did not modulate multimodal integration. First, upregulation of multimodal integration is not possible using tDCS over the PPC as the integration process already functions at maximum capacity. Second, prefrontal decision-making areas may have overruled any modulated input from the PPC as it may not have matched their decision-making criterion and compensated for the modulation.
处理模棱两可的情况是日常生活中的一项持续挑战，需要整合来自不同模态的感觉输入，以形成对环境的连贯心理表征。弹跳/流幻觉可以用来研究多模态环境的模糊感知和处理。简而言之，当声音与两个移动圆盘的重叠时刻一致时，报告弹跳而不是流的印象的可能性会增加。神经影像学研究表明，右后顶叶皮层在跨模态整合中至关重要，并且在弹跳/流幻觉期间活跃。因此，在本研究中，我们使用经颅直流电刺激来刺激该脑区。在主动刺激条件下，将 9 cm 电极放置在 P4-EEG 位置上，将 35 cm 参考电极放置在左上臂上。刺激持续 15 分钟。每位参与者在三个时间点完成弹跳/流任务：刺激前、刺激期间和刺激后。在一个由 N=60 名健康年轻成年人组成的样本中，我们没有发现阳极 tDCS 的影响。贝叶斯分析显示，tDCS 效应的证据非常有力。阳极 tDCS 未调节多模态整合的原因有两个可能的解释。首先，由于整合过程已经达到最大容量，因此不可能使用 PPC 上的阳极 tDCS 来上调多模态整合。其次，前额叶决策区域可能已经否决了来自 PPC 的任何调制输入，因为它可能不符合他们的决策标准，并补偿了调制。
