Cruikshank S J, Weinberger N M
Center for the Neurobiology of Learning and Memory, University of California, Irvine 92717, USA.
J Neurosci. 1996 Jan 15;16(2):861-75. doi: 10.1523/JNEUROSCI.16-02-00861.1996.
The goal of this experiment was to evaluate the role of cellular interactions postulated by the Hebbian, or covariance, hypothesis in the induction of receptive-field (RF) plasticity in the adult auditory cortex (ACx). This was accomplished by determining whether a "covariance treatment" (see below) was sufficient to induce RF plasticity without behavioral experiences that normally induce such plasticity. During the covariance treatment (conducted in urethane-anesthetized adult guinea pigs), one tone was paired with excitatory juxtacellular current, applied to a single postsynaptic cell in the primary ACx. Excitatory current increased postsynaptic discharge, thereby increasing covariance between activity of the postsynaptic cell and its afferents that were activated by the tone. In alternation, within the same cell a second, different tone was paired with inhibitory juxtacellular current, decreasing covariance between the postsynaptic cell and afferents activated by the second tone. After treatment, responses to tones associated with increased covariance strengthened significantly relative to tones associated with decreased covariance, as predicted by the Hebbian hypothesis. This occurred in 7 of 22 (32%) cells undergoing 120 pairing trials, but in only 4 of 38 (11%) cells undergoing 60 trials. Fewer than 5% of cells showed significant effects opposite those predicted by the hypothesis. Significant plasticity lasted > or = 15 min. Probability of plasticity was significantly higher when the cortical electroencephalogram was nonsynchronized during treatment (5/9 cells) than when synchronized (2/13 cells). These findings support the role of presynaptic-postsynaptic covariance processes in the induction of adult neocortical RF plasticity and suggest that factors associated with cortical state "gate" such plasticity.
本实验的目的是评估赫布（Hebbian）假说或协方差假说所假定的细胞间相互作用在成年听觉皮层（ACx）感受野（RF）可塑性诱导中的作用。这是通过确定“协方差处理”（见下文）是否足以在没有通常诱导这种可塑性的行为经验的情况下诱导RF可塑性来实现的。在协方差处理过程中（在氨基甲酸乙酯麻醉的成年豚鼠中进行），将一个音调与施加到初级ACx中单个突触后细胞的兴奋性细胞旁电流配对。兴奋性电流增加突触后放电，从而增加突触后细胞及其由该音调激活的传入神经活动之间的协方差。交替地，在同一个细胞内，将第二个不同的音调与抑制性细胞旁电流配对，减少突触后细胞与由第二个音调激活的传入神经之间的协方差。处理后，如赫布假说所预测的，与协方差增加相关的音调的反应相对于与协方差降低相关的音调显著增强。在接受120次配对试验的22个细胞中有7个（32%）出现这种情况，但在接受60次试验的38个细胞中只有4个（11%）出现这种情况。不到5%的细胞表现出与假说预测相反的显著效应。显著的可塑性持续≥15分钟。当处理期间皮层脑电图不同步时（5/9个细胞），可塑性的概率显著高于同步时（2/13个细胞）。这些发现支持了突触前 - 突触后协方差过程在成年新皮层RF可塑性诱导中的作用，并表明与皮层状态相关的因素“控制”这种可塑性。
