Cognition and Behaviour, Donders Institute for Brain, Radboud University Nijmegen Nijmegen, Netherlands ; Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf Hamburg, Germany.
Cognition and Behaviour, Donders Institute for Brain, Radboud University Nijmegen Nijmegen, Netherlands.
Front Hum Neurosci. 2014 Jun 17;8:446. doi: 10.3389/fnhum.2014.00446. eCollection 2014.
Alpha (8-12 Hz) and beta band (18-30 Hz) oscillations have been implicated in sensory anticipation and motor preparation. Here, using magneto-encephalography, we tested whether they have distinct functional roles in a saccade task that induces a remapping between sensory and motor reference frames. With a crossed hands posture, subjects had to saccade as fast and accurate as possible toward a tactile stimulus delivered to one of two non-visible index fingers, located to the left or right of gaze. Previous studies have shown that this task, in which the somatotopic stimulus must be remapped to activate oculomotor system in the opposing hemisphere, is occasionally preceded by intrahemispheric remapping, driving a premature saccade into the wrong direction. To test whether the brain could anticipate the remapping, we provided auditory predictive cues (80% validity), which indicated which finger is most likely to be stimulated. Both frequency bands showed different lateralization profiles at central vs. posterior sensors, indicating anticipation of somatosensory and oculomotor processing. Furthermore, beta band power in somatosensory cortex correlated positively with saccade reaction time (SRT), with correlation values that were significantly higher with contralateral vs. ipsilateral activation. In contrast, alpha band power in parietal cortex correlated negatively with SRT, with correlation values that were significantly more negative with ipsilateral than contralateral activation. These results suggest distinct functional roles of beta and alpha band activity: (1) somatosensory gating by beta oscillations, increasing excitability in contralateral somatosensory cortex (positive correlation); and (2) oculomotor gating by posterior alpha oscillations, inhibiting gaze-centered oculomotor regions involved in generating the saccade to the wrong direction (negative correlation). Our results show that low frequency rhythms gate upcoming sensorimotor transformations.
阿尔法（8-12Hz）和贝塔波段（18-30Hz）的震荡被认为与感觉预期和运动准备有关。在这里，我们使用脑磁图来测试它们在一个扫视任务中是否具有不同的功能作用，该任务会在感觉和运动参考框架之间产生重新映射。在交叉手的姿势下，被试必须尽快、尽可能准确地向触觉刺激物扫视，该刺激物位于视线左侧或右侧的两个不可见食指之一。以前的研究表明，在这个任务中，躯体感觉刺激必须重新映射到对侧半球的眼动系统才能激活，偶尔会出现半球内重新映射，导致过早的扫视进入错误的方向。为了测试大脑是否可以预测重新映射，我们提供了听觉预测线索（80%的有效性），指示最有可能刺激哪个手指。两个频带在中央与后部传感器之间显示出不同的侧化分布，表明对躯体感觉和眼动处理的预期。此外，躯体感觉皮层中的β波段功率与扫视反应时间（SRT）呈正相关，与对侧激活的相关值明显高于同侧激活的相关值。相比之下，顶叶皮层中的α波段功率与 SRT 呈负相关，与同侧激活的相关值明显更负。这些结果表明β和α波段活动具有不同的功能作用：（1）β震荡对躯体感觉的门控作用，增加对侧躯体感觉皮层的兴奋性（正相关）；（2）后部α震荡对眼动的门控作用，抑制了参与产生错误方向扫视的以注视为中心的眼动区域（负相关）。我们的结果表明，低频节律可以对即将到来的感觉运动转换进行门控。
