1 Department of Neurology, Mayo Clinic, 200 First St SW, Rochester MN, 55905, USA.
1 Department of Neurology, Mayo Clinic, 200 First St SW, Rochester MN, 55905, USA2 International Clinical Research Center, St. Anne's University Hospital, Pekarska 53, Brno 656 91, Czech Republic.
Brain. 2014 Aug;137(Pt 8):2231-44. doi: 10.1093/brain/awu149. Epub 2014 Jun 11.
High frequency oscillations are associated with normal brain function, but also increasingly recognized as potential biomarkers of the epileptogenic brain. Their role in human cognition has been predominantly studied in classical gamma frequencies (30-100 Hz), which reflect neuronal network coordination involved in attention, learning and memory. Invasive brain recordings in animals and humans demonstrate that physiological oscillations extend beyond the gamma frequency range, but their function in human cognitive processing has not been fully elucidated. Here we investigate high frequency oscillations spanning the high gamma (50-125 Hz), ripple (125-250 Hz) and fast ripple (250-500 Hz) frequency bands using intracranial recordings from 12 patients (five males and seven females, age 21-63 years) during memory encoding and recall of a series of affectively charged images. Presentation of the images induced high frequency oscillations in all three studied bands within the primary visual, limbic and higher order cortical regions in a sequence consistent with the visual processing stream. These induced oscillations were detected on individual electrodes localized in the amygdala, hippocampus and specific neocortical areas, revealing discrete oscillations of characteristic frequency, duration and latency from image presentation. Memory encoding and recall significantly modulated the number of induced high gamma, ripple and fast ripple detections in the studied structures, which was greater in the primary sensory areas during the encoding (Wilcoxon rank sum test, P = 0.002) and in the higher-order cortical association areas during the recall (Wilcoxon rank sum test, P = 0.001) of memorized images. Furthermore, the induced high gamma, ripple and fast ripple responses discriminated the encoded and the affectively charged images. In summary, our results show that high frequency oscillations, spanning a wide range of frequencies, are associated with memory processing and generated along distributed cortical and limbic brain regions. These findings support an important role for fast network synchronization in human cognition and extend our understanding of normal physiological brain activity during memory processing.
高频振荡与正常大脑功能有关，但也越来越被认为是致痫性大脑的潜在生物标志物。它们在人类认知中的作用主要在经典的伽马频率（30-100 Hz）范围内进行研究，反映了涉及注意力、学习和记忆的神经元网络协调。动物和人类的脑内记录表明，生理振荡超出了伽马频率范围，但它们在人类认知处理中的功能尚未完全阐明。在这里，我们使用 12 名患者（5 名男性和 7 名女性，年龄 21-63 岁）的颅内记录，在一系列情感负荷图像的记忆编码和回忆过程中，研究了跨越高伽马（50-125 Hz）、涟漪（125-250 Hz）和快速涟漪（250-500 Hz）频段的高频振荡。图像呈现诱导了初级视觉、边缘和高级皮质区域中所有三个研究频段的高频振荡，其序列与视觉处理流一致。这些诱导的振荡在位于杏仁核、海马体和特定新皮质区域的个体电极上被检测到，从图像呈现开始，就显示出特征频率、持续时间和潜伏期的离散振荡。记忆编码和回忆显著调节了所研究结构中诱导的高伽马、涟漪和快速涟漪检测的数量，在编码过程中（Wilcoxon 秩和检验，P=0.002），在记忆图像的回忆过程中（Wilcoxon 秩和检验，P=0.001），主要感觉区域中的检测数量更多。此外，诱导的高伽马、涟漪和快速涟漪反应区分了编码和情感负荷的图像。总之，我们的结果表明，跨越广泛频率范围的高频振荡与记忆处理有关，并在分布式皮质和边缘大脑区域中产生。这些发现支持快速网络同步在人类认知中的重要作用，并扩展了我们对记忆处理过程中正常生理脑活动的理解。
