Shevelev I A, Eysel U T, Lazareva N A, Sharaev G A
Department of Sensory Physiology, Russian Academy of Sciences, Moscow, Russia.
Neuroscience. 1998 May;84(1):11-23. doi: 10.1016/s0306-4522(97)00363-1.
Orientation tuning of some neurons in cat visual cortex (area 17) revealed successive shifts of the preferred orientation and widening of tuning in time during the first 150 ms after onset of a flashing light bar. The mechanisms of these dynamics and the possible role of intracortical inhibition are still under discussion. In this study we analysed the dynamics using the time slice method before and during blockade of GABAergic inhibition by microiontophoretic application of bicuculline and observed two main types of neuronal behaviour. The first group of neurons (39 of 68 units or 57.4%) with relatively sharp tuning and absence or relatively small shifts of preferred orientation under control conditions increased or developed this shift during bicuculline application. Changes in tuning were observed between 30 and 150 ms after stimulus onset when inhibition was blocked. Neurons of the second group (29 units or 42.6% of cases) displayed pronounced shifts of preferred orientation under control conditions which was typically diminished or lost during blockade of inhibition. The results indicate different contributions of intracortical inhibition to different neurons distinguishing by stability or time dependence of their orientation preference during normal response generation. In one group of striate cells orientation tuning was kept narrow and constant in time by intracortical inhibition, while in another group orientation tuning dynamics are induced by inhibitory mechanisms.
猫视觉皮层（17区）中一些神经元的朝向调谐显示，在闪光光条出现后的最初150毫秒内，偏好朝向会连续变化，调谐宽度也会随时间变宽。这些动态变化的机制以及皮质内抑制可能发挥的作用仍在讨论之中。在本研究中，我们使用时间切片法分析了在通过微量离子电泳施加荷包牡丹碱阻断GABA能抑制之前和期间的动态变化，并观察到两种主要的神经元行为类型。第一组神经元（68个单位中的39个，即57.4%）在对照条件下具有相对尖锐的调谐，偏好朝向没有变化或变化相对较小，在施加荷包牡丹碱期间这种变化增加或出现。在抑制被阻断后，刺激开始后30至150毫秒之间观察到调谐变化。第二组神经元（29个单位，占病例的42.6%）在对照条件下表现出明显的偏好朝向变化，在抑制阻断期间这种变化通常会减弱或消失。结果表明，在正常反应产生过程中，皮质内抑制对不同神经元的贡献不同，这些神经元根据其朝向偏好的稳定性或时间依赖性而有所区别。在一组纹状细胞中，皮质内抑制使朝向调谐在时间上保持狭窄且恒定，而在另一组中，朝向调谐动态变化是由抑制机制诱导的。
