Faramarzi Maryam, Kasten Florian H, Altaş Gamze, Aleman André, Ćurčić-Blake Branislava, Herrmann Christoph S
Experimental Psychology Lab, Department of Psychology, European Medical School, Cluster of Excellence "Hearing4All," Carl von Ossietzky University, Oldenburg, Germany.
Department of Biomedical Sciences of Cells and Systems, Cognitive Neuroscience Center, University of Groningen, University Medical Center Groningen, Groningen, Netherlands.
Front Neurosci. 2021 Apr 1;15:602437. doi: 10.3389/fnins.2021.602437. eCollection 2021.
Hallucinations and illusions are two instances of perceptual experiences illustrating how perception might diverge from external sensory stimulations and be generated or altered based on internal brain states. The occurrence of these phenomena is not constrained to patient populations. Similar experiences can be elicited in healthy subjects by means of suitable experimental procedures. Studying the neural mechanisms underlying these experiences not only has the potential to expand our understanding of the brain's perceptual machinery but also of how it might get impaired. In the current study, we employed an auditory signal detection task to induce auditory illusions by presenting speech snippets at near detection threshold intensity embedded in noise. We investigated the neural correlates of auditory false perceptions by examining the EEG activity preceding the responses in speech absent (false alarm, FA) trials and comparing them to speech present (hit) trials. The results of the comparison of event-related potentials (ERPs) in the activation period vs. baseline revealed the presence of an early negativity (EN) and a late positivity (LP) similar in both hits and FAs, which were absent in misses, correct rejections (CR) and control button presses (BPs). We postulate that the EN and the LP might represent the auditory awareness negativity (AAN) and centro-parietal positivity (CPP) or P300, respectively. The event-related spectral perturbations (ERSPs) exhibited a common power enhancement in low frequencies (<4 Hz) in hits and FAs. The low-frequency power enhancement has been frequently shown to be accompanied with P300 as well as separately being a marker of perceptual awareness, referred to as slow cortical potentials (SCP). Furthermore, the comparison of hits vs. FAs showed a significantly higher LP amplitude and low frequency power in hits compared to FAs. Generally, the observed patterns in the present results resembled some of the major neural correlates associated with perceptual awareness in previous studies. Our findings provide evidence that the neural correlates associated with conscious perception, can be elicited in similar ways in both presence and absence of externally presented sensory stimuli. The present findings did not reveal any pre-stimulus alpha and beta modulations distinguishing conscious vs. unconscious perceptions.
幻觉和错觉是两种感知体验的实例，说明了感知如何与外部感官刺激产生差异，并基于大脑内部状态而产生或改变。这些现象的发生并不局限于患者群体。通过适当的实验程序，在健康受试者中也能引发类似的体验。研究这些体验背后的神经机制，不仅有可能扩展我们对大脑感知机制的理解，还能让我们了解其可能受损的方式。在当前的研究中，我们采用了一种听觉信号检测任务，通过在噪声中以接近检测阈值强度呈现语音片段来诱发听觉错觉。我们通过检查无语音（误报，FA）试验中反应之前的脑电图（EEG）活动，并将其与有语音（命中）试验进行比较，来研究听觉错误感知的神经关联。激活期与基线期事件相关电位（ERP）的比较结果显示，命中和误报中均存在早期负波（EN）和晚期正波（LP），而漏报、正确拒绝（CR）和控制按钮按压（BP）中则不存在。我们推测，EN和LP可能分别代表听觉意识负波（AAN）和中央顶叶正波（CPP）或P300。事件相关频谱扰动（ERSP）在命中和误报中均表现出低频（<4Hz）的共同功率增强。低频功率增强经常被证明与P300同时出现，并且单独作为感知意识的一个标志，被称为慢皮层电位（SCP）。此外，命中与误报的比较显示，命中的LP振幅和低频功率明显高于误报。一般来说，本研究结果中观察到的模式类似于先前研究中与感知意识相关的一些主要神经关联。我们的研究结果提供了证据，表明与有意识感知相关的神经关联，在外部呈现的感官刺激存在和不存在的情况下，都可以以类似的方式诱发。目前的研究结果没有揭示任何区分有意识与无意识感知的刺激前α和β调制。
