大鼠外侧膝状体神经元时空频率调谐特性发育观察

Development of spatiotemporai frequency turning in rat lateral geniculate neuron

背景外侧膝状体（LGN）是视觉通路中重要的视觉信息处理器官，近年来发现LGN参与运动视觉信息处理，功能磁共振成像检查表明在LGN水平存在着双眼竞争，可能与弱视的发生有关。然而，LGN神经元时空频率特性的研究多限于猴或者猫，大鼠的相关研究较少。目的观察不同年龄段大鼠LGN神经元感受野时空频率调谐特性。方法取睁眼后14—16d组、20～22d组、27～30d组及睁眼后60d组Wistar大鼠各5只，用在体细胞外记录技术，通过正弦光栅视觉刺激分别对各组大鼠LGN神经元感受野时空调谐特性进行检测，观察大鼠LGN神经元时空频率调谐特性随着发育发生的动态变化。结果睁眼后14—16d组、20～22d组、27～30d组及睁眼后60d组大鼠LGN神经元时间和空间频率调谐低通调制和带通调制间神经元数量的差异均无统计学意义（，=0．68、0．47，P〉0．05），4个组大鼠LGN神经元感受野最优时间频率调谐特性成年后达最高值，大鼠LGN神经元的最优时间频率均值分别为（2．5±1．3）、（2．6±1．2）、（2．6±1．1）、（3．6＋1．1）Hz，差异有统计学意义（，=4．53，P〈0．05），睁眼后60d组的最优时间频率明显高于睁眼后14—16d组、20～22d组、27～30d组，差异均有统计学意义（q=4．43、4．10、4．03，P〈0．05），睁眼后14～16d组、20～22d组、27～30d组间的相互比较差异均无统计学意义（P〉0．05）。4个组大鼠LGN神经元的最优空间频率均值分别为（0．04±0．04）、（0．04±0．03）、（0．05±0．03）、（0．05±0．04）cpd，差异均无统计学意义（F=0．58，P〉0．05），而时间频率瞬时带宽及空间频率带宽各年龄组问比较，差异均无统计学意义（F=0．37、1．22，P〉0．05）。结论大鼠LGN神经元感受野时空频率调谐发育特性的不同可能与其在视觉通路中的功能有关。

Background Recent researches suggested that properties of neurons in the lateral geniculate neuron （LGN） may represent an important neural limitation on the development of basic spatial and temporal vision, and even binocular rivalry. However, previous studies on the properties of spatiotemporal frequency tuning of LGN were rather concentrated on a monkey or cat,whereas little is known about rat. Objective This study was to examine the development of spatiotemporal frequency tuning in rats LGN. Methods Twenty Wistar rats were collected and divided into 14-16 day, 20-22 day, 27-30 day and 60 day groups according to the different ages after their eyes opened and 5 rats were assigned for each group. Extracellular single neuron recording was carried out in the rats to study the spatio-temporal receptive field properties of neurons in LGN by sinusoidal gratings visual stimuli. Dynamic changes of the spatio-temporal receptive field properties of neurons in LGN with the development of Wistar rats were evaluated. Results The differences between band-pass and low-pass distribution of temporal frequency or spatial frequency of rat LGN were not statistically significant （X2 = O. 68,0.47 ,P〉0. 05 ）. The optimal temporal frequency of receptive field in rat LGN went up to the maximum value until 60 day in Wistar rats. The mean optimal temporal frequencies of neurons in the four different age groups were （2.5 ± 1.3 ） , （2.6± 1.2） , （2.6± 1. l ） and （ 3.6± 1.1 ） Hz with significant differences among the 4 groups （F= 4.53,P〈0. 05 ） , and those in the 14-16 day group,20-22 day group,27-30 day group were significantly lower than in the 60 days group （q = 4.43,4. 10,4. 03, P〈 0.05 ）. No significant differences were seen among the 14-16 day group ,20-22 day group and 27-30 day group （P〉0. 05 ）. The optimal spatial frequency values in the four groups were （ 0. 04 ± 0. 04 ） , （ 0.04 ± 0. 03 ） , （ 0. 05 ± 0.03 ） , （ 0.05 ± 0. 04） epd,respectively without statistical difference among them （ F = 0. 58, P 〉 0. 05 ）. The temporal and spatial bandwidth values in the various age groups were not statistically significant among the four groups （ F = 0.37,1.22, P〉0. 05）. Conclusions The development of temporal and spatial frequency characteristics of the rat LGN receptive field may be related to its functional visual pathway.