Department of Psychology, University of British Columbia, Vancouver, Canada.
PLoS One. 2010 Dec 16;5(12):e14371. doi: 10.1371/journal.pone.0014371.
Neural synchronization is a mechanism whereby functionally specific brain regions establish transient networks for perception, cognition, and action. Direct addition of weak noise (fast random fluctuations) to various neural systems enhances synchronization through the mechanism of stochastic resonance (SR). Moreover, SR also occurs in human perception, cognition, and action. Perception, cognition, and action are closely correlated with, and may depend upon, synchronized oscillations within specialized brain networks. We tested the hypothesis that SR-mediated neural synchronization occurs within and between functionally relevant brain areas and thus could be responsible for behavioral SR. We measured the 40-Hz transient response of the human auditory cortex to brief pure tones. This response arises when the ongoing, random-phase, 40-Hz activity of a group of tuned neurons in the auditory cortex becomes synchronized in response to the onset of an above-threshold sound at its "preferred" frequency. We presented a stream of near-threshold standard sounds in various levels of added broadband noise and measured subjects' 40-Hz response to the standards in a deviant-detection paradigm using high-density EEG. We used independent component analysis and dipole fitting to locate neural sources of the 40-Hz response in bilateral auditory cortex, left posterior cingulate cortex and left superior frontal gyrus. We found that added noise enhanced the 40-Hz response in all these areas. Moreover, added noise also increased the synchronization between these regions in alpha and gamma frequency bands both during and after the 40-Hz response. Our results demonstrate neural SR in several functionally specific brain regions, including areas not traditionally thought to contribute to the auditory 40-Hz transient response. In addition, we demonstrated SR in the synchronization between these brain regions. Thus, both intra- and inter-regional synchronization of neural activity are facilitated by the addition of moderate amounts of random noise. Because the noise levels in the brain fluctuate with arousal system activity, particularly across sleep-wake cycles, optimal neural noise levels, and thus SR, could be involved in optimizing the formation of task-relevant brain networks at several scales under normal conditions.
神经同步是一种机制，通过该机制，功能特定的大脑区域为感知、认知和行动建立暂时的网络。向各种神经系统直接添加弱噪声（快速随机波动）通过随机共振（SR）的机制增强同步。此外，SR 也发生在人类的感知、认知和行动中。感知、认知和行动与专门的大脑网络内的同步振荡密切相关，并且可能依赖于这些同步振荡。我们测试了这样一个假设，即 SR 介导的神经同步发生在功能相关的大脑区域内和之间，因此可能是行为 SR 的原因。我们测量了人类听觉皮层对短暂纯音的 40-Hz 瞬态响应。当听觉皮层中一组调谐神经元的持续、随机相位 40-Hz 活动由于其“最佳”频率的阈上声音的出现而同步时，就会产生这种响应。我们在各种水平的附加宽带噪声下呈现接近阈值的标准声音流，并在使用高密度 EEG 的偏离检测范式中测量了受试者对标准声音的 40-Hz 响应。我们使用独立成分分析和偶极拟合来定位双侧听觉皮层、左后扣带回皮层和左额上回中 40-Hz 反应的神经源。我们发现，添加噪声会增强所有这些区域的 40-Hz 反应。此外，添加噪声还增加了 40-Hz 反应期间和之后，在 alpha 和 gamma 频带中这些区域之间的同步。我们的结果表明，在几个功能特定的大脑区域中存在神经 SR，包括传统上不认为对听觉 40-Hz 瞬态反应有贡献的区域。此外，我们还证明了这些大脑区域之间的同步存在 SR。因此，适量随机噪声的添加促进了神经活动的内部和区域间同步。由于大脑中的噪声水平随唤醒系统活动而波动，特别是在睡眠-觉醒周期中，最佳神经噪声水平，因此 SR，可能参与在正常情况下优化几个尺度上与任务相关的大脑网络的形成。
