Frequency modulation of neural oscillations according to visual task demands
Frequency modulation of neural oscillations according to visual task demands
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DOI：
10.1073/pnas.1713318115
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发表时间：
2018-02-06
影响因子：
11.1
通讯作者：
Samaha, Jason
中科院分区：
文献类型：
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作者：
Wutz, Andreas;Melcher, David;Samaha, Jason
视觉感知中的时间整合被认为发生在枕部阿尔法频段(8-12赫兹)振荡的周期内。当连续的刺激落在相同的阿尔法周期内时，它们可以被整合，并为不同的阿尔法周期分离。因此，阿尔法振荡的速度与感知的时间分辨率相关，因此较低的阿尔法频率为感知整合提供了更长的时间窗口，而较高的阿尔法频率对应于更快的采样和分离。大脑的节律性活动能否被动态控制，以根据不同的视觉任务需求调整其处理速度？我们记录了脑磁图(MEG)，当参与者在时间整合和分离的任务指令、保持刺激和任务难度不变的任务指令之间切换时。我们发现，与分离相比，当视觉任务要求时间整合时，α振荡的峰值频率降低。阿尔法频率在刺激处理之前和过程中立即被战略性地调制，这表明了一种预备性的自上而下的调制来源。其神经发生部位位于枕叶和颞下皮质。频率调制是专门针对阿尔法振荡的，并且在增量(1-3赫兹)、β(3-7赫兹)、贝塔(15-30赫兹)或伽马(30-50赫兹)频率范围内不发生。这些结果表明，α频率受到自上而下的控制，以增加或降低视觉感知的时间分辨率。
Temporal integration in visual perception is thought to occur within cycles of occipital alpha-band (8-12 Hz) oscillations. Successive stimuli may be integrated when they fall within the same alpha cycle and segregated for different alpha cycles. Consequently, the speed of alpha oscillations correlates with the temporal resolution of perception, such that lower alpha frequencies provide longer time windows for perceptual integration and higher alpha frequencies correspond to faster sampling and segregation. Can the brain's rhythmic activity be dynamically controlled to adjust its processing speed according to different visual task demands? We recorded magnetoencephalography (MEG) while participants switched between task instructions for temporal integration and segregation, holding stimuli and task difficulty constant. We found that the peak frequency of alpha oscillations decreased when visual task demands required temporal integration compared with segregation. Alpha frequency was strategically modulated immediately before and during stimulus processing, suggesting a preparatory top-down source of modulation. Its neural generators were located in occipital and inferotemporal cortex. The frequency modulation was specific to alpha oscillations and did not occur in the delta (1-3 Hz), theta (3-7 Hz), beta (15-30 Hz), or gamma (30-50 Hz) frequency range. These results show that alpha frequency is under top-down control to increase or decrease the temporal resolution of visual perception.