Melloni Lucia, Molina Carlos, Pena Marcela, Torres David, Singer Wolf, Rodriguez Eugenio
Laboratorio de Neurociencias, Escuela de Psicología, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, San Joaquin, 8940000 Santiago, Chile.
J Neurosci. 2007 Mar 14;27(11):2858-65. doi: 10.1523/JNEUROSCI.4623-06.2007.
Subliminal stimuli can be deeply processed and activate similar brain areas as consciously perceived stimuli. This raises the question which signatures of neural activity critically differentiate conscious from unconscious processing. Transient synchronization of neural activity has been proposed as a neural correlate of conscious perception. Here we test this proposal by comparing the electrophysiological responses related to the processing of visible and invisible words in a delayed matching to sample task. Both perceived and nonperceived words caused a similar increase of local (gamma) oscillations in the EEG, but only perceived words induced a transient long-distance synchronization of gamma oscillations across widely separated regions of the brain. After this transient period of temporal coordination, the electrographic signatures of conscious and unconscious processes continue to diverge. Only words reported as perceived induced (1) enhanced theta oscillations over frontal regions during the maintenance interval, (2) an increase of the P300 component of the event-related potential, and (3) an increase in power and phase synchrony of gamma oscillations before the anticipated presentation of the test word. We propose that the critical process mediating the access to conscious perception is the early transient global increase of phase synchrony of oscillatory activity in the gamma frequency range.
阈下刺激能够被深度加工，并激活与有意识感知刺激时相似的脑区。这就引出了一个问题：神经活动的哪些特征能够关键地区分有意识加工和无意识加工。神经活动的瞬态同步已被提出作为有意识感知的神经关联物。在此，我们通过比较在延迟样本匹配任务中与可见和不可见单词加工相关的电生理反应来检验这一假设。被感知和未被感知的单词都会使脑电图中局部（伽马）振荡出现类似的增加，但只有被感知的单词会在大脑广泛分离的区域诱发伽马振荡的瞬态长距离同步。在这个短暂的时间协调期之后，有意识和无意识加工的电图特征继续出现差异。只有被报告为被感知的单词会诱发：（1）在维持间隔期间额叶区域增强的θ振荡；（2）事件相关电位的P300成分增加；以及（3）在预期呈现测试单词之前伽马振荡的功率和相位同步增加。我们提出，介导进入有意识感知的关键过程是伽马频率范围内振荡活动相位同步的早期瞬态全局增加。
