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首页> 外文期刊>Journal of Neurophysiology >Reorganization in awake rat auditory cortex by local microstimulation and its effect on frequency-discrimination behavior.
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Reorganization in awake rat auditory cortex by local microstimulation and its effect on frequency-discrimination behavior.

机译：清醒大鼠听觉皮层的局部微刺激重组及其对频率区分行为的影响。

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In common with other sensory cortices, the mammalian primary auditory cortex (AI) demonstrates the capacity for large-scale reorganization following many experimental situations. For example, training animals in frequency-discrimination tasks has been shown to result in an increase in cortical frequency representation. Such central changes-most commonly, an increase in central representation of specific stimulus parameters-have been hypothesized to underlie the improvements in perceptual acuity (perceptual learning) seen in many learning situations. The actual behavioral relevance of central reorganizations, however, remains speculative. Here, we directly examine this issue. We first show that stimulating the AI cortex of the awake rat with a weak electric current (intracortical microstimulation or ICMS) has the effect of inducing central reorganizations similar to those accompanying the traditional plasticity experiments (a result previously noted only in anesthetized preparations). Depending on the site of AI stimulation, ICMS enlarged the cortical representation of certain frequencies. Next we examined the direct perceptual consequences of ICMS-induced AI reorganization for the rat's ability to discriminate frequencies. Over the course of the experiment, we also detailed, and made comparisons between, the frequency-response characteristics of rat AI cortex in the awake and ketamine-anesthetized animal. AI cells that responded to pure tones were divided into two categories--strongly and weakly responsive--based on the strength of their evoked discharge. Individual cells maintained their respective response strengths in both awake and anesthetized conditions. Strongly responsive cells showed at least four different temporal responses and tended to be narrowly tuned. Their responses were stable over the long term. In general frequency-response characteristics were qualitatively similar in the anesthetized and awake animal; bandwidths tended to be broader in awake animals. Although both strong and weak cell populations respond to tones, only the strongly responsive cells fit into a tonotopically organized scheme. By contrast, weakly responsive cells did not exhibit a frequency mapping and may represent a more diffuse input to AI than that underlying strongly responsive cells. In general, the overall frequency organization of AI was found to be equally well expressed in both the awake and anesthetized rat. ICMS reorganization of AI did not alter frequency-discrimination behavior in the rat--either signal detectability or response bias--suggesting that an increase in central representation, by itself, is insufficient to account for perceptual learning. It is likely that cortical reorganizations that accompany perceptual learning are strongly keyed to specific behavioral contexts.
机译：与其他感觉皮质相同，哺乳动物的初级听觉皮层（AI）展示了在许多实验情况下进行大规模重组的能力。例如，对动物进行频率区分任务的训练已显示导致皮质频率表示的增加。假设这种中心变化（最常见的是特定刺激参数的中心表示的增加）是许多学习情况下感知敏锐度（感知学习）改善的基础。但是，中央重组的实际行为相关性仍是推测性的。在这里，我们直接研究这个问题。我们首先表明，用弱电流刺激清醒大鼠的AI皮质（皮层内微刺激或ICMS）具有诱导中心重组的作用，类似于传统可塑性实验所伴随的结果（以前仅在麻醉制剂中才注意到这一结果）。根据AI刺激的部位，ICMS扩大了某些频率的皮层表示。接下来，我们检查了ICMS诱导的AI重组对大鼠辨别频率的能力的直接感知结果。在实验过程中，我们还详细介绍了在清醒和氯胺酮麻醉下的大鼠AI皮质的频率响应特性，并进行了比较。根据纯音诱发的放电强度，对纯音有反应的AI细胞分为两类-强和弱反应。单个细胞在清醒和麻醉条件下均保持各自的响应强度。强反应性细胞表现出至少四种不同的时间反应，并且倾向于窄调。从长远来看，他们的反应是稳定的。总的来说，麻醉和清醒动物的频率响应特性在质量上相似。清醒动物的带宽往往更宽。尽管强和弱细胞群体都对音调做出反应，但是只有强反应细胞才能适应音调组织的方案。相比之下，弱反应性细胞没有表现出频率映射，并且与潜在的强反应性细胞相比，可能代表着更多的AI输入。通常，在清醒和麻醉的大鼠中都发现了AI的整体频率组织同样良好的表达。 ICMS对AI的重组没有改变大鼠的频率区分行为-无论是信号可检测性还是反应偏差-暗示中心表达的增加本身不足以说明感知学习。伴随知觉学习的皮层重组很可能强烈地锁定于特定的行为背景。

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