Kaiser Jochen, Lutzenberger Werner
MEG-Center, Institute of Medical Psychology and Behavioral Neurobiology, Eberhard-Karls-University of Tübingen, Germany.
Neuroscientist. 2003 Dec;9(6):475-84. doi: 10.1177/1073858403259137.
Oscillatory activity in the gamma-band range has been related both to gestalt perception and to cognitive functions such as attention, learning, and memory. After giving a brief account of recent findings from electroencephalography and intracortical recordings, the present review will focus on spectral activity in the magnetoencephalogram. Here, gamma-band effects are topographically more local and involve higher frequencies than in the electroencephalogram. Bottom-up-driven auditory spatial mismatch detection elicits gamma-band activity over posterior parietal cortex, whereas auditory pattern mismatch processing leads to gamma-band enhancements over anterior temporal and inferior frontal regions. These topographies support representations of auditory spatial and pattern information in the putative dual auditory "where" and "what" pathways, respectively. During top-down-guided auditory spatial and pattern-working memory tasks, prefrontal gamma-band increases are observed in addition to activations over putative auditory stream areas. Moreover, stimulus maintenance in working memory is accompanied by coherence increases between sensory and prefrontal regions. Gamma-band topographies in magnetoencephalogram are highly comparable with hemodynamic brain imaging studies but yield additional information on the temporal dynamics of activations and connectivity patterns. In summary, magnetoencephalographic gamma-band activity revealed both local synchronization patterns and cortico-cortical interactions accompanying cognitive processes at a good spatial and high temporal resolution.
γ频段范围内的振荡活动与格式塔感知以及注意力、学习和记忆等认知功能都有关联。在简要介绍脑电图和皮层内记录的近期研究结果之后，本综述将聚焦于脑磁图中的频谱活动。在此，γ频段效应在地形学上更为局部，且涉及比脑电图更高的频率。自下而上驱动的听觉空间失配检测会在顶叶后皮质引发γ频段活动，而听觉模式失配处理则会导致颞叶前部和额叶下部区域的γ频段增强。这些地形图分别支持了在假定的双听觉“哪里”和“什么”通路中听觉空间和模式信息的表征。在自上而下引导的听觉空间和模式工作记忆任务期间，除了在假定的听觉流区域有激活外，还观察到前额叶γ频段增加。此外，工作记忆中的刺激维持伴随着感觉区域和前额叶区域之间连贯性的增加。脑磁图中的γ频段地形图与血液动力学脑成像研究高度可比，但能提供有关激活和连接模式时间动态的额外信息。总之，脑磁图γ频段活动在良好的空间和高时间分辨率下揭示了伴随认知过程的局部同步模式和皮质 - 皮质相互作用。
