认知与发展心理学研究室知识库

神经可塑性是人类大脑的一种内在属性，它在发育过程中达到最大，随着年龄的增长而下降。眼优势可塑性是一种被广泛研究的视觉可塑性。近来大量的短时程单眼剥夺研究表明视觉系统在成熟后仍具有眼优势可塑性。纵观已有的短时程单眼剥夺研究，发现皆采用非自然的实验室合成刺激测量短时程单眼剥夺前后的眼优势。自然场景刺激有更复杂的统计特性，可能涉及与简单实验室刺激截然不同的皮层机制。因此，一个尚未解决的问题是短时程单眼剥夺已有的研究发现是否可以推广到以自然融合场景为刺激的测试中。而且，已有研究都采用剥夺前和剥夺后的测试范式，鲜有研究关注剥夺过程中眼优势是否发生变化以及如何变化。在本文中，我们利用基于自然场景刺激的稳态视觉诱发电位（SSVEP）技术和瞳孔测量技术进一步研究短时程单眼剥夺的神经机制。此外，鲜有研究关注眼间注意不平衡和眼间时间延迟是否会对眼优势产生影响，在本文中我们设计多种新颖的单眼剥夺范式来研究以上问题。

本文开展了四个部分的研究：

第一部分研究中通过基于自然场景刺激SSVEP 技术测量剥夺前后和剥夺过程中神经眼优势的变化。研究结果发现：用自然融合刺激测试发现两个小时的单眼剥夺使得剥夺眼相比非剥夺眼振幅显著增大，表明剥夺提高了剥夺眼的神经增益。在剥夺过程中，剥夺眼与非剥夺眼的振幅比值随着时间显著增大，表明剥夺眼的神经增益逐渐增强。

第二部分研究关注短时程单眼剥夺对瞳孔振荡的影响。我们的研究结果并未发现短时程模拟遮盖剥夺和相位规则剥夺对瞳孔振荡产生影响。

第三部分研究考察了注意在单眼剥夺中的作用。研究结果显示：当用附加的注意任务研究对单眼剥夺效应的调节时，注意任务的引入直接干扰到剥夺效果，提示自上而下的注意在单眼剥夺中的潜在贡献。而倒放视频剥夺实验发现在保证两眼输入基本相同的前提下，仅单眼注意（自上而下任务驱动的）的剥夺就可以使得剥夺眼在双眼竞争任务中变得更加占主导。

第四部分研究关注眼间延迟适应对单眼视听整合和知觉眼优势的影响。研究结果表明，眼间延迟适应使得延迟眼的视听整合偏向声音提前。而用双眼相位整合和双眼竞争任务测得眼间延迟适应对知觉眼优势没有影响。

综上，本文揭示了短时程单眼剥夺效应可以在观看自然场景刺激时表现出来，为单眼剥夺中的稳态补偿机制理论拓展到一般性的自然场景刺激提供了证据。同时，我们用基于自然场景的SSVEP 技术跟踪剥夺过程中眼优势逐渐变化的过程，这一方法有望在未来作为实时追踪自然适应环境下神经反应的一种强有力手段。

此外，本文揭示了单眼注意的剥夺同样可以产生剥夺效果，提示高级脑区对初级视觉皮层的反馈在眼优势可塑性中的重要作用，开辟了单眼剥夺研究领域的新方向，有利于我们深入理解成年期眼优势可塑性的背后机制。

Neuroplasticity is an intrinsic property of the brain that is maximal during development but decreases in adulthood. Ocular dominance plasticity is an important aspect of visual plasticity and has been widely studied. Recently abundant investigations on short-term monocular deprivation have demonstrated that the visual system still retains ocular dominance plasticity beyond the critical period. To our knowledge, all previous work adopted non-natural synthetic stimuli in testing ocular dominance before and after the short-term monocular deprivation. It is recognized that natural scene stimuli have more complex statistical properties and may engage cortical mechanisms substantially different from simple synthetic stimuli. Therefore, an unsolved question is whether reshaping of ocular dominance following monocular deprivation could be applied during perception of natural scene stimuli without conspicuous interocular competition. Moreover, all the past work on monocular deprivation adopts a paradigm of pre- and post-testing. It remains largely unknown whether and how the ocular dominance changes during the deprivation. Using the technique of natural-scene-based steady-state visual evoked potentials (SSVEPs) and pupillometry, we further studied the neural mechanism of short-term monocular deprivation. In addition, few studies have focused on whether interocular attention imbalance and interocular time delay have an effect on ocular dominance. In the current study, we designed a variety of novel paradigms on monocular deprivation to investigate the above questions.

This thesis is composed of four studies:

In the first study, using the natural-scene-based SSVEP we measured the neural ocular dominance not only before and after the deprivation but also during the deprivation. The results showed that two hours of monocular deprivation significantly increased the amplitude of the deprived eye compared to the non-deprived eye, indicating monocular deprivation boosted the neural gain for the deprived eye. During the deprivation, the amplitude ratio between the deprived eye and the non-deprived eye increased significantly over time, indicating a progressive increase of neural gain for the deprived eye.

In the second study, we focused on the effect of short-term monocular deprivation on pupil oscillations. Our results showed that both the mean-luminance and pink-noise deprivation have no effect on pupil oscillations.

In the third study, we investigated the role of attention in monocular deprivation.The results showed that when using an additional attention task to modulate the monocular deprivation effect, the attentional task introduced direct interference to the deprivation effect, indicating the potential contribution of top-down attention to monocular deprivation. The experiment of “backwards movie” deprivation found that on the premise that inputs from two eyes were basically the same, an imbalance of attention (top-down task-driven) between the two eyes could make the unattended eye become more dominant in the binocular rivalry task.

In the fourth study, we studied the effect of interocular delay adaptation on the monocular audiovisual integration and perceptual ocular dominance. The results showed that interocular delay adaptation biased the audiovisual integration of the delayed eye to “audio first”. The interocular delay adaptation had no effect on perceptual ocular dominance which were measured with binocular phase combination and binocular rivalry task.

In summary, our results revealed that the effects of short-term monocular deprivation could manifest when viewing natural scenes, providing a natural case in support of the homeostatic compensation theory of monocular deprivation. At the same time, using the natural-scene-based SSVEP technique we revealed the gradual change of neural ocular dominance during the deprivation, suggesting that this method could be used as a powerful tool to track the neural response to the natural adapting environment in real time in the future. In addition, our findings revealed that the deprivation of attention in one eye could also produce the deprivation effect, suggesting that the feedback from the higher-level brain regions to the primary visual cortex may play an important role in ocular dominance plasticity, thus bring a new broad of perspective on monocular deprivation study and may accelerate a deeper understanding of the underlying mechanism of the ocular dominance plasticity in adulthood.