In vivo imaging of supragranular circuit plasticity in mouse visual cortex

描述（由申请人提供）：本提案旨在研究单眼剥夺期间小鼠初级视觉皮层中双眼反应的经验依赖性重组的细胞基质。采用的方法是纵向测量单个转基因小鼠眼特异性反应和神经回路解剖变化的有效手段：(1)经颅本征信号光学成像，(2)钙指示荧光和遗传标记神经元的双光子显微镜。先前的研究发现，颗粒外层是介导快速的、活动依赖的视觉皮层可塑性的位点，其解剖学变化的速度和幅度与视觉反应的变化相当。在本研究中，我们将通过描述在单眼剥夺过程中，初级视觉皮层双眼区遗传标记的核上兴奋性神经元亚群在体内发生的生理和解剖学变化，对这一现象进行更详细的研究。由于小鼠初级视觉皮层缺乏眼优势柱，功能双光子显微镜将用于将单眼剥夺期间发生的单个遗传标记神经元的眼特异性反应与相应的解剖变化联系起来。生理和解剖变化将在单眼剥夺的三个时间上不同的阶段中表现出来：(1)对被剥夺的眼睛的反应丧失，(2)睁开的眼睛反应急剧增加，被剥夺的眼睛反应略有增加，(3)重新打开被剥夺的眼睛后反应恢复到初始状态。这一建议的成功将提供对视觉皮层可塑性过程中发生的变化的深入理解，并为未来研究揭示发育早期和成人可塑性的分子机制奠定了基础。此外，阐明视觉皮质可塑性的基础是支持后天性脑异常（如弱视）治疗的基础问题。

DESCRIPTION (provided by applicant): This proposal seeks to investigate the cellular substrates that underlie the experience-dependent reorganization of binocular responses in the mouse primary visual cortex during monocular deprivation. The methods to be used are efficient means of measuring changes in eye-specific responses and neural circuit anatomy longitudinally in individual transgenic mice: (1) transcranial intrinsic signal optical imaging, and (2) two-photon microscopy of calcium indicator fluorescence and genetically labeled neurons. Previous studies have found extragranular layers to be the locus mediating rapid, activity-dependent visual cortical plasticity, with anatomical changes comparable in speed and magnitude to the change in visual responses. In this proposal, this phenomenon will be investigated in greater detail by characterizing the physiological and anatomical changes occurring in vivo in subsets of genetically labeled supragranular excitatory neurons in the binocular zone of the primary visual cortex during monocular deprivation. Since the mouse primary visual cortex is devoid of ocular dominance columns, functional two-photon microscopy will be used to correlate eye-specific responses of singly, genetically labeled neurons with corresponding anatomical changes as they occur during monocular deprivation. The physiological and anatomical changes will be characterized in the context of three temporally distinct phases of monocular deprivation: (1) loss of response to the deprived eye, (2) a dramatic increase in open eye response and a slight increase in deprived eye response, and (3) a return of responses to their initial state after re-opening the deprived eye. The success of this proposal would provide an in-depth understanding of the changes that occur during visual cortical plasticity and could unveil a canvas for future studies investigating the molecular mechanisms that underlie plasticity early in development and in adult. Moreover, elucidating the substrates of visual cortical plasticity is a fundamental issue that supports the basis for treatment of acquired brain abnormalities (e.g. amblyopia).