Sackler Centre for Consciousness Science, University of Sussex, Brighton, UK; Department of Psychology, University of Sussex, Brighton, UK; Institute of Psychology, University of Bern and Distance Learning University, Switzerland.
Sackler Centre for Consciousness Science, University of Sussex, Brighton, UK; Department of Informatics, University of Sussex, Brighton, UK.
Neuropsychologia. 2018 Mar;111:151-162. doi: 10.1016/j.neuropsychologia.2018.01.030. Epub 2018 Jan 31.
Synesthesia is associated with additional perceptual experiences, which are automatically and consistently triggered by specific inducing stimuli. Synesthesia is also accompanied by more general sensory and cortical changes, including enhanced modality-specific cortical excitability. Extensive cognitive training has been shown to generate synesthesia-like phenomenology but whether these experiences are accompanied by neurophysiological changes characteristic of synesthesia remains unknown. Addressing this question provides a unique opportunity to elucidate the neural basis of perceptual plasticity relevant to conscious experiences. Here we investigate whether extensive training of letter-color associations leads not only to synesthetic experiences, but also to changes in cortical excitability. We confirm that overtraining synesthetic associations results in synesthetic phenomenology. Stroop tasks further reveal synesthesia-like performance following training. Electroencephalography and transcranial magnetic stimulation show, respectively, enhanced visual evoked potentials (in response to untrained patterns) and lower phosphene thresholds, demonstrating specific cortical changes. An active (using letter-symbol training) and a passive control confirmed these results were due to letter-color training and not simply to repeated testing. Summarizing, we demonstrate specific cortical changes, following training-induced acquisition of synesthetic phenomenology that are characteristic of genuine synesthesia. Collectively, our data reveal dramatic plasticity in human visual perception, expressed through a coordinated set of behavioral, neurophysiological, and phenomenological changes.
联觉是与额外的知觉体验相关联的，这些体验是由特定的诱发刺激自动且一致地触发的。联觉还伴随着更一般的感觉和皮质变化，包括增强的模态特异性皮质兴奋性。广泛的认知训练已被证明可以产生类似联觉的现象学，但这些体验是否伴随着联觉特有的神经生理变化尚不清楚。解决这个问题提供了一个独特的机会，可以阐明与意识体验相关的感知可塑性的神经基础。在这里，我们研究了广泛的字母-颜色联想训练是否不仅会导致联觉体验，还会导致皮质兴奋性的变化。我们证实，过度训练联觉联想会导致联觉现象学。Stroop 任务进一步揭示了训练后的类似联觉的表现。脑电图和经颅磁刺激分别显示增强的视觉诱发电位（对未训练的模式）和更低的闪光阈值，表明特定的皮质变化。一项主动（使用字母-符号训练）和一项被动控制证实，这些结果是由于字母-颜色训练，而不仅仅是重复测试。总之，我们证明了特定的皮质变化，在训练诱导的联觉现象学获得之后，这些变化是真正联觉的特征。总的来说，我们的数据揭示了人类视觉感知的巨大可塑性，表现为一系列协调的行为、神经生理和现象学变化。
