猫初级视皮层神经元的双眼整合反应特性研究

Binocular integration of binocular neurons in striate cortex of kitten

背景来自双眼视觉信号经视网膜、外侧膝状体直至初级视皮层融汇到单个细胞，构成双跟驱动细胞。双眼驱动细胞对双眼视觉信息进行整合和编码并介导高级视皮层产生融合和立体视觉，视觉发育关键期内的异常视觉经验常导致弱视和双眼整合反应的损害。目的观察幼猫初级视皮层双眼驱动细胞对来自双眼视觉信号的整合反应特性。方法选用3只8～10周健康幼猫，采用在体细胞外记录技术和双眼分视刺激方法，观察麻醉和肌肉麻痹状态下幼猫初级视皮层V1区28个电极记录部位的双眼驱动细胞对光栅刺激的峰电位发放率和局部场电位Gamma频率（20～90Hz）的振荡幅度，计算并比较两种信号的眼优势指数（ODI）和双眼整合指数（BI]），观察细胞对双跟分别刺激的反应是否平衡及对双眼整合反应大小的影响。结果在具双眼特性的28个细胞中，锋电位信号的眼优势绝对值较场电位的眼优势绝对值大（t=2．606，P=0．021）；锋电位和场电位的ODI呈正相关（R^2=0．513，F=27．423，P=0．003），双眼整合作用主要表现为易化，锋电位的BII（2．348±0．996）较场电位的BII（3．678±1．974）小，差异有统计学意义（t=2．671，P=0．019），对于锋电位信号，双眼平衡组的易化反应较双眼不平衡组高，差异有统计学意义（t=-2．519，P：0．035），对于场电位信号，双眼平衡组的易化反应较双眼不平衡组高，但差异无统计学意义（t=-1．671，P=0．146）。结论在正常发育的幼猫初级视皮层，神经元对来自双眼感受野内相同视刺激的整合作用主要表现为易化，且易化水平依赖于神经元对双眼分别的视刺激反应是否平衡，场电位信号和锋电位信号从不同皮层空间范围和来源成分反映了双眼整合的神绎机制。

Background The integration of segregated pathways from the two eyes first appears in V1 neurons,where it not only plays a critical role in the generation of a three-dimensional visual representation. Abnormal visual experiences in critical period usually lead to amblyopia and binocular integration defects. Objective Present study was to investigate how neurons of kitten coordinate their activity patterns in response to synchronous dichoptic stimulus inputs in striate cortex. Methods Spike rate and local field potential（LFP） gamma band （20-90 Hz） power of three kitten （1-1.2 Kg,8-l0 weeks old） to monocular and synchronous diehoptic presented gratings were assessed for 28 binocular neurons in VI of kitten by in vivo extracellular record method under anaesthesia and paralysis. Ocular dominance index （ODI） and binocular integration index （BII） were assessed and the correlation between these two indexes were analyzed. Results in 28 cells with binocular characteristic, the absolute value of spike-ODI was significant larger than that of LFP-ODI（ t = 2. 606, P = 0.021 ）. A positive linear correlation between the ocular preferences of spike and LFP was found （ R^2 = 0. 513, F = 27. 423, P = 0. 003 ）. In dichotic trails, binocular facilitation with BII for spike was 2. 348±0. 996, showing a significant reduce in comparison with BII for LFP （3. 678± 1. 974）（ t = 2. 671 ,P= 0. 019 ）. Binocular integration index for two signals were greater when monocular responses of both eyes were similar （ P = O. 035 and P = 0. 124, respectively）. Conclusion Both spike rate and gamma band power of LFP exhibited binocular facilitation to synchronous presented dichotic stimuli with significant facilitation induced by balanced monocular responses. Spiking activity and LFP reflect neural activities of different spatial scales and source components.