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视觉节律对知觉转换的影响及其神经机制
其他题名The underlying neural mechanisms and the effect of visual rhythm modulating bistable perceptual alternations
张雪
学位类型博士
导师蒋毅
2016-05
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业心理学
关键词两可知觉 节律 生物运动 运动频率 旋转球 神经振荡-外界节律 同步化
摘要两可知觉是指同一个视觉刺激能引起两种可能的知觉。在长时间观察两可刺激后,尽管刺激没变,但观察者的意识会在两种可能的刺激间来回切换。本研究利用这种刺激,通过一系列行为实验,功能成像和电生理实验探索人类视觉意识的动态变化受有节律刺激的频率调节的现象及其背后的机制。
研究共分三部分。
在第一部分中,我们采用生物运动这种两可刺激,操纵其运动频率,发现运动频率能线性地调节知觉转换的频次。并采用两可旋转球模拟生物运动以及赋予旋转球有规律的节奏运动或亮度变化进一步发现有节奏的视觉信息的频率能影响知觉转换的频次。
第二部分中,我们利用fMRI技术扫描观察者在观察有节律的生物运动和匀速的旋转球时的脑活动,发现左右MT(Middle Temporal,中颞)区参与了两种刺激的知觉转换的过程。该区域的自然地知觉转换的活动只在知觉从正对转向背对观察者前,才会强于外源性的知觉转换对应的活动。且心理生理交互作用分析,发现生物运动在此方向内源性转换相比外源性的转换,会激发右前额与左侧MT更强的连接。这一发现部分揭示了有节律的运动引起的知觉转换相关的脑机制。
第三部分研究,利用EEG电生理技术采用有节奏的运动的两可旋转球,验证了我们关于知觉转换受运动频率调节可能涉及到神经振荡-外界节律同步化现象的猜想。即会随着外界刺激的频率的增加而增强的同步化可能在这个过程中发挥着关键作用。我们发现观察两可知觉的过程中在枕叶及右侧枕顶存在显著的同步化现象。进一步分析发现知觉转换与同步化的强度,以及被同步的神经振荡与刺激波动的相位一致性的波动都相关。分析知觉转换前的活动,还发现被同步的低频活动会通过相位调节与知觉转换相关的高频的alpha活动的幅度。这部分研究证明了有节律的运动引起的知觉转换与神经振荡-外界节律同步化的关系,并回答了知觉转换是如何受神经振荡-外界节律同步化影响的。
综上所述,本研究发现意识的动态变化并不是随机的,它可以受到外界刺激的频率性的调节。这种调节机制在有节律的运动的视知觉中尤其突出。暗示频率性信息在视知觉中的重要性。另外,我们的研究还揭示了这一现象背后的神经机制,这为我们理解知觉转换提供了更丰富的线索。
其他摘要Some ambiguous visual stimuli can produce two percepts. During observing such bistable stimuli for a long time, our perception would involuntarily alternate between two percepts, in spite of no change happened to the stimulus. We adopted such stimuli, using psychophysical, fMRI (functional Magnetic Resonance Imaging), and EEG (electroencephalogram) techniques, to explore how the dynamics of human visual consciousness could be regulated by rhythmic properties and investigated the neural mechanisms underlying such phenomenon.
The study was consisted of three parts.
First, we adopted bistable biological motion (BM) stimuli and manipulated their motion cycle. We found that motion cycle could regulate the perceptual alternation rates of BM linearly. Further experiments using bistable rotating sphere revealed that rhythmic visual information was the key factor that modulates perceptual alternation rates.
Second, we applied fMRI to scan the brain activities when observing BM stimuli and bistable rotational sphere. The former contains rhythmic motion and the latter rotates at constant speed. We found that the area MT (Middle Temporal) played a key role in the process of perceptual alternation. Specifically, the activities in this area were stronger before the spontaneous perceptual alternation than the artificial perceptual alternation, only when percepts were switched from facing toward observers to away from observer. Moreover, psychophysiological interaction analysis revealed that, in this perceptual switching direction, during spontaneous perceptual alternation, only for rhythmic BM, the connection between the left MT and right prefrontal cortex was stronger than that for artificial perceptual alternation. These findings partially illustrated the neural mechanisms underlying the phenomenon that rhythmic motion can modulate perceptual alternations.
Third, we probed the electrophysiological activities during viewing bistable sphere rotating rhythmically. We noticed a phenomenon called neural entrainment whose strength could increase with the cycle of stimuli. Thus we speculated that the neural entrainment at the stimulus frequency may contribute to the linear relationship between the motion cycle and perceptual alternations observed in part one. As we expected, neural entrainment was widely distributed in occipital and the right occipitoparietal areas. Further analyses revealed that the number of perceptual alternation was correlated with the strength of neural entrainment and also correlated with the dynamics of the phase locking between entrained neural oscillation and stimulus wave. We further analyzed the EEG before perceptual alternation, and found that the entrained neural oscillation could phase-amplitude couple with the alpha amplitude which reflects the bottom-up destabilization of perception. Our finding demonstrated the neural entrainment underlying the effect we observed above and gave out an explanation about how perceptual alternation was modulated by motion cycle.
In conclusion,our studies found the dynamics of human consciousness was not random, but susceptible to the regular rhythmic information, especially in visual motion stimuli. In addition, our study also revealed the neural mechanism underlying this phenomenon, providing rich clues for understanding perceptual alternation.
学科领域基础心理学
语种中文
文献类型学位论文
条目标识符http://ir.psych.ac.cn/handle/311026/20679
专题健康与遗传心理学研究室
作者单位中国科学院心理研究所
推荐引用方式
GB/T 7714
张雪. 视觉节律对知觉转换的影响及其神经机制[D]. 北京. 中国科学院研究生院,2016.
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