【作者】 刘再群；

【导师】 华田苗；

【作者基本信息】 安徽师范大学 ， 动物学， 2003， 硕士

【摘要】 成体脑存在显著的可塑性。学习诱导的可塑性是指动物学习两个事件之间的联系而产生的脑对特定信息处理功能的改变并能随之调整本身行为的现象。感觉系统中，在丘脑和／或皮层水平都观察到神经元对有意义刺激的再调谐或者向着有意义刺激出现的皮层代表区地域图(Map)重组。对每一个感觉模式的分析显示，学习诱导的感觉可塑性和行为结果(Performance)之间是否相关具有任务依赖性。 听觉和躯体感觉系统中的可塑性包括感受野可塑性、2-脱氧葡萄糖(2-DG)标记的Map改变。在视觉系统，尚无学习中感受野和Map改变的分析，可塑性证据部分来自学习过程中观察到的神经元反应的改变。视觉信号识别训练可改变视觉通路神经元的可塑性，其神经机制尚不清楚。 本实验训练两只成年猫分别进行水平和垂直方位的静止正弦光栅的识别以获得食物奖赏，两只猫的行为识别能力随着训练时间的延续显著提高，4个月后识别的正确率达85％以上，用与训练方位垂直的正弦光栅检测发现，识别正确率明显下降。细胞外记录外膝体背核神经元对不同方位正弦光栅刺激的反应发现，与对照猫相比，行为猫外膝体细胞的最优方位(PO)并末向着训练方位发生改变，但对于感受野位于离中央凹10-15度视角的细胞来说，其方位选择性强度较正常猫显著增大，且在训练方位的发放数均比正常猫明显减少。以上结果提示，方位识别训练可特异性改变外膝体部分神经元(特定离心度上)的方位敏感性，这种敏感性改变可能对视皮层细胞的方位编码可塑性有贡献。更多还原

【Abstract】 The adult brain shows remarkable plasticity, learning-induced plasticity is that an awake animal learns the association between two events and modifies processing ability of its brian to specific information and thus change its behavior as a function of the learned association. Across sensory modalities, the re-tuning of neurons to a significant stimulus or map reorganizations in favor of the significant stimuli were observed at the thalamic and/or cortical level. The analysis of the literature in each sensory modality indicates that relationships between learning-induced sensory plasticity and behavioral performance can, or cannot, be found depending on the tasks that were used.Receptive field (RF) plasticity, 2DG and map changes obtained in the auditory and somatosensory system are reviewed. In the visual system, as there is no RF and map analysis during learning per se, the evidence presented are from increased neuronal responsiveness, and from the effects of perceptual learning in human and non human primates. Practising visual signal discrimination can change neural plasticity in the visual pathway, the mechanism of which remains unknown.In the present experiment, two adult cats were trained to discriminate respectively the horizontal and vertical static sinusoidal gratings for food reward. Performance of the two cats improved significantly with the extension of training, all reaching a percent correct above 85% after 4 months. Testing with an orientation orthogonal to the trained orientation showed that correct performance of the two cats decreased obviously. Extracellular recording the responses of dLGN neurons to sinusoidal gratings with different orientations revealed that, compared with that in untrained cat, preferred orientations of dLGN neurons in trained cats did not shift in favor of the trained orientation. However, for cells whose receptive fields located at the position of 10°-15° visual acute away from the fovals, trained cats showed distinguished increase in orientation selectivity and significant decrease in spike counts at trained orientation compared with that in untrained cat. The result above indicates that orientation discrimination practising can leads to specific shift of orientation sensitivity for at least part of the dLGN neurons, which may contribute to the neural plasticity of orientation coding in visual cortex.更多还原