Ohl F W, Scheich H
Federal Institue for Neurobiology, Brenneckestrasse 6, D-39118 Magdeburg, Germany.
Eur J Neurosci. 1996 May;8(5):1001-17. doi: 10.1111/j.1460-9568.1996.tb01587.x.
Differential aversive auditory conditioning in the awake Mongolian gerbil was performed during single- and multi-unit recording in field Al of the primary auditory cortex. Presentations of pure tone stimuli of a given frequency (reinforced conditioned stimulus; CS+) paired with electrocutaneous stimulation (unconditioned stimulus) were combined with several other non-reinforced tone stimuli (non-reinforced conditioned stimulus; CS-). Stimulus presentation during training and testing was optimized for constancy of the probability of occurrence of both the CS+ and the CS- stimulus. The paradigm led to a reorganization of both the spectral and temporal response characteristics of auditory cortical neurons with the following basic results. First, tone-evoked responses of Al neurons recorded after multiple acoustic stimulation under these conditions varied statistically around a mean value (stationarity). Conditioning produced a shift in mean values of evoked responses. The altered tone responses were also stationary (stability of the plastic effects). Second, the frequency-receptive fields (FRFs) of neurons were reorganized in a frequency-specific way such that the CS+ frequency became located in a local minimum of the FRF after training. This resulted from a training-induced increase in the responses to frequencies adjacent to the CS+ frequency in the FRF relative to the CS+ response. The effect can be interpreted as an enhancement of the 'spectral contrast' sensitivity of the unit in the CS+ neighbourhood. Third, apart from this frequency-specific plastic effect, responses to other frequencies also underwent changes during training. The non-frequency-specific changes were not generally predictable but the post-trial responses were stationary. Fourth, the analysis of the long-term behaviour of FRF reorganization revealed the stability of plastic effects under retention training and the gradual re-establishment of the pretrial FRF during extinction training. Fifth, not only the spectral characteristics but also the temporal structure of the tone-evoked responses could be affected by the training. In most cases the training-induced changes measured within the first tens of milliseconds of the response corresponded to the response changes obtained by integration over the total response period. There were some cases, however, in which the direction of the response change varied with time, indicating that excitatory and inhibitory influences on the temporal response pattern were differently affected by training.
在清醒的蒙古沙鼠中进行差异厌恶听觉条件反射实验，实验过程中对初级听觉皮层A1区进行单神经元和多神经元记录。将给定频率的纯音刺激（强化条件刺激；CS+）与皮肤电刺激（非条件刺激）配对呈现，并与其他几种非强化音调刺激（非强化条件刺激；CS-）相结合。训练和测试期间的刺激呈现经过优化，以确保CS+和CS-刺激出现概率的稳定性。该范式导致听觉皮层神经元的频谱和时间响应特性发生重组，基本结果如下。第一，在这些条件下多次声刺激后记录的A1神经元的音调诱发反应在平均值周围有统计学变化（平稳性）。条件反射使诱发反应的平均值发生了偏移。改变后的音调反应也是平稳的（可塑性效应的稳定性）。第二，神经元频率感受野（FRF）以频率特异性方式重组，使得训练后CS+频率位于FRF的局部最小值处。这是由于训练导致FRF中与CS+频率相邻的频率的反应相对于CS+反应增加所致。这种效应可解释为该单元在CS+邻域的“频谱对比度”敏感性增强。第三除了这种频率特异性可塑性效应外，训练期间对其他频率的反应也发生了变化。非频率特异性变化通常不可预测，但试验后的反应是平稳的。第四，对FRF重组的长期行为分析表明，在保留训练下可塑性效应具有稳定性，而在消退训练期间预试验FRF会逐渐重新建立。第五，不仅频谱特性，而且音调诱发反应的时间结构也可能受到训练的影响。在大多数情况下，在反应的前几十毫秒内测量的训练诱导变化与在整个反应期积分获得的反应变化相对应。然而，在某些情况下，反应变化的方向随时间而变化，这表明训练对时间反应模式的兴奋性和抑制性影响有所不同。
