Auditory Neurophysiology Laboratory, Institute of Neuroscience of Castilla y León, University of Salamanca Salamanca, Spain.
Front Neural Circuits. 2012 Dec 27;6:107. doi: 10.3389/fncir.2012.00107. eCollection 2012.
Stimulus-specific adaptation (SSA) is the ability of some neurons to respond better to rare than to frequent, repetitive stimuli. In the auditory system, SSA has been found at the level of the midbrain, thalamus, and cortex. While previous studies have used the whole overall neuronal response to characterize SSA, here we present a detailed analysis on the variations within the time course of the evoked responses. The extracellular activity of well isolated single neurons from the inferior colliculus (IC) was recorded during stimulation using an oddball paradigm, which is able to elicit SSA. At the same time, these responses were evaluated before, during, and after the microiontophoretic application of gabazine, a specific antagonist of GABA(A) receptors, to study the contribution of inhibition to the responses of these neurons. We then analyzed the difference signal (DS), which is the difference in the PSTH in response to rare and frequent stimuli. We found that, even in a sample of neurons showing strong SSA (i.e., showing larger preference for rare stimuli), the DS was variable and one third of the neurons contained portions that responded significantly better to the frequent stimuli than to the rare. This variability is not observed when averaging the responses of multiple cells. Furthermore, the blockade of GABA(A) receptors increased the number of neurons showing portions that responded better to the frequent stimuli, indicating that inhibition in the IC refines and sharpens SSA in the neural responses.
刺激特异性适应（SSA）是指一些神经元对稀有而非频繁重复刺激的反应更好的能力。在听觉系统中，SSA 已在中脑、丘脑和皮层水平上被发现。虽然之前的研究使用整体神经元反应来描述 SSA，但在这里，我们对诱发反应的时间过程中的变化进行了详细分析。在使用能够引起 SSA 的Oddball 范式进行刺激期间，记录了来自下丘（IC）的高度分离的单个神经元的细胞外活动。同时，在微电泳应用 GABA(A)受体特异性拮抗剂 Gabazine 前后，对这些反应进行评估，以研究抑制作用对这些神经元反应的贡献。然后，我们分析了差分信号（DS），即对稀有和频繁刺激的 PSTH 的差异。我们发现，即使在显示强烈 SSA（即对稀有刺激表现出更大偏好）的神经元样本中，DS 也是可变的，三分之一的神经元包含部分对频繁刺激的反应明显优于稀有刺激。当平均多个细胞的反应时，不会观察到这种可变性。此外，GABA(A)受体的阻断增加了表现出对频繁刺激反应更好的部分的神经元数量，表明 IC 中的抑制作用可以细化和锐化神经反应中的 SSA。
