Temporal perceptual learning (TPL) constitutes a unique and profound demonstration of neural plasticity within the brain. Our understanding for the neurometabolic changes associated with TPL on the other hand has been limited in part by the use of traditional fMRI approaches. Since plasticity in the visual cortex has been shown to underlie perceptual learning of visual information, we tested the hypothesis that TPL of an auditory interval involves a similar change in plasticity of the auditory pathway and if so, whether these changes take place in a lower-order sensory-specific brain area such as the primary auditory cortex (A1), or a higher-order modality-independent brain area such as the inferior parietal cortex (IPC). This distinction will inform us of the mechanisms underlying perceptual learning as well as the locus of change as it relates to TPL. In the present study, we took advantage of a new technique: proton magnetic resonance spectroscopy (MRS) in combination with psychophysical measures to provide the first evidence of changes in neurometabolic processing following 5 days of temporal discrimination training. We measured the (E)xcitation-to-(I)nhibition ratio as an index of learning in the right IPC and left A1 while participants learned an auditory two-tone discrimination task. During the first day of training, we found a significant task-related increase in functional E/I ratio within the IPC. While the A1 exhibited the opposite pattern of neurochemical activity, this relationship did not reach statistical significance. After timing performance has reached a plateau, there were no further changes to functional E/I. These findings support the hypothesis that improvements in temporal discrimination relies on neuroplastic changes in the IPC, but it is possible that both areas work synergistically to acquire a temporal interval.

中文翻译：

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兴奋-抑制平衡的转变是时间辨别知觉学习的基础

时间感知学习（TPL）是大脑内神经可塑性的独特而深刻的证明。另一方面，我们对与 TPL 相关的神经代谢变化的理解部分受到传统功能磁共振成像方法使用的限制。由于视觉皮层的可塑性已被证明是视觉信息感知学习的基础，因此我们测试了听觉间隔的 TPL 涉及听觉通路可塑性的类似变化的假设，如果是这样，这些变化是否发生在较低的区域中。顺序感觉特定的大脑区域，例如初级听觉皮层（A1），或高阶模态独立的大脑区域，例如下顶叶皮层（IPC）。这种区别将告诉我们感知学习的潜在机制以及与 TPL 相关的变化轨迹。在本研究中，我们利用一种新技术：质子磁共振波谱 (MRS) 与心理物理学测量相结合，提供了 5 天时间辨别训练后神经代谢过程变化的第一个证据。当参与者学习听觉双音辨别任务时，我们测量了 (E) 兴奋与 (I) 抑制比率作为右侧 IPC 和左侧 A1 的学习指数。在培训的第一天，我们发现 IPC 内与任务相关的功能 E/I 比率显着增加。虽然 A1 表现出相反的神经化学活性模式，但这种关系并未达到统计学显着性。在计时性能达到稳定水平后，功能 E/I 没有进一步的变化。这些发现支持这样的假设：时间辨别力的改善依赖于 IPC 中的神经可塑性变化，但这两个区域有可能协同工作以获得时间间隔。