色觉信号影响视皮层感知光学离焦的功能磁共振研究

Sustained defocus of retinal image has been shown to be associated with the onset and progression of myopia. It has also been reported in our previous studies that monochromatic light has the potential to induce myopia. However, the mechanism involving the central nervous system behind both of these two findings remains inconclusive. On the basis of the previous studies that have focused on the effects of chromatic signals on the blur sensitivity of accommodative system and accommodative microfluctuations, the present study aims at investigating the cortical mechanism of chromatic signal that influences the blur sensitivity of visual system. The functional magnetic resonance imaging technique such as the blood-oxygen-level-dependent contrast and Magnetic Resonance Spectroscopy will be applied to observe the neural responses, neural transmitters concentrations and retinotopic characteristics of human visual cortex induced by specially designed visual stimuli, i.e. different chromatic, spatial frequency, contrast and vergence information, The effects of optical defocus, accommodation, cycloplegia, and chromatic adaptation will also be studied in subgroups. Psychophysical experiments will be conducted to explore the spectral sensitivity, accommodative microfluctuations and accommodative blur sensitivity and blur detection threshold under various chromatic conditions. This study would to some extent further shed light on the causal mechanism underlying myopia development. New prevention measures and treatment modalities for myopia that are related to color and optical defocus can thus be expected.

持续存在视网膜离焦可致近视发展，申请者团队已证实单色光对近视发生发展也有作用，但两者中枢机制均不明确。本项目在已获得色觉信号对调节系统感知光学离焦的模糊敏感度和调节稳定性均存在影响的研究基础上，旨在探讨色觉信号对视觉中枢感知视网膜离焦敏感度的调控作用，及不同波长色光间的相互作用，利用功能磁共振技术的微血管内血氧水平变化（BOLD） 及磁共振波谱技术（MRS）活体检测特殊设计的视觉刺激诱导的人眼视觉皮层神经元激活水平、视网膜拓扑定位和神经递质代谢水平及分布，控制视觉刺激的颜色、离焦度、空间频率、对比度等信息和给予分组干预（色觉适应、光学离焦、调节麻痹），结合色觉敏感度、调节微波动和调节模糊敏感度、模糊感知阈值等心理物理学检测，有望获得视觉中枢对色觉-离焦复合信号的调控变化，并可为近视防治提供色光及离焦途径防控的新思路。

本项目采用心理物理学方法和功能磁共振技术对色觉正常人眼视觉系统的色觉信号和模糊感知通道的交互作用进行了研究。通过呈现不同波长光谱分布的颜色视标，检测调节刺激反应曲线、调节微波动、客观焦深和主观焦深，比较了不同色觉通路对调节系统和主观认知系统感知视网膜光学离焦的影响。并通过功能磁共振检测，探索了色觉通路和形觉通路的交互影响。研究内容包含三个部分：第一部分：正常色觉被试对带有不同色觉信息的视网膜离焦信号的感知和调节功能及色觉适应的影响；第二部分：正常色觉被试对带有不同色觉信息的视网膜离焦信号的主观感知阈值及色觉适应的影响；第三部分：色觉适应对视网膜离焦（模糊）感知和色觉适应的功能磁共振研究。综合以上三个实验内容，本项目发现，色觉信号可有效诱导形觉信号的感知。调节系统对于混合色光即黑白视标的调节反应最敏感，可能与色像差的参与有关。不同色觉通路之间比较，L/M锥通路（红绿）的调节系统模糊敏感度较低，通过色觉适应可显著增加。主观神经感知系统对于光学离焦的感知则以红绿视标最为敏感，即主观模糊敏感度在L/M锥通路最敏感，且适应后可显著提升。功能磁共振证实了色觉适应后视皮层对红绿视标的感知信号增强的现象，并发现以周边视野的激活为主，提示色觉信号对干预视觉系统对于光学离焦的处理也发生在皮层水平，但具体作用模式尚有待进一步研究。