Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, California.
Department of Otolaryngology-Head and Neck Surgery, University Hospital Magdeburg, Otto-von-Guericke University, Magdeburg, Germany.
J Neurophysiol. 2020 Dec 1;124(6):1798-1814. doi: 10.1152/jn.00278.2020. Epub 2020 Sep 30.
Auditory experience and behavioral training can modify perceptual performance. However, the consequences of temporal perceptual learning for temporal and spectral neural processing remain unclear. Specifically, the attributes of neural plasticity that underlie task generalization in behavioral performance remain uncertain. To assess the relationship between behavioral and neural plasticity, we evaluated neuronal temporal processing and spectral tuning in primary auditory cortex (AI) of anesthetized owl monkeys trained to discriminate increases in the envelope frequency (e.g., 4-Hz standard vs. >5-Hz targets) of sinusoidally amplitude-modulated (SAM) 1-kHz or 2-kHz carriers. Behavioral and neuronal performance generalization was evaluated for carriers ranging from 0.5 kHz to 8 kHz. Psychophysical thresholds revealed high SAM discrimination acuity for carriers from one octave below to ∼0.6 octave above the trained carrier frequency. However, generalization of SAM discrimination learning progressively declined for carrier frequencies >0.6 octave above the trained carrier frequency. Neural responses in AI showed that SAM discrimination training resulted in ) increases in temporal modulation preference, especially at carriers close to the trained frequency, ) narrowing of spectral tuning for neurons with characteristic frequencies near the trained carrier frequency, potentially limiting spectral generalization of temporal training effects, and ) enhancement of firing-rate contrast for rewarded versus nonrewarded SAM frequencies, providing a potential cue for behavioral temporal discrimination near the trained carrier frequency. Our findings suggest that temporal training at a specific spectral location sharpens local frequency tuning, thus, confining the training effects to a narrow frequency range and limiting generalization of temporal discrimination learning across a wider frequency range. Monkeys' ability to generalize amplitude modulation discrimination to nontrained carriers was limited to one octave below and 0.6 octave above the trained carrier frequency. Asymmetric generalization was paralleled by sharpening in cortical spectral tuning and enhanced firing-rate contrast between rewarded and nonrewarded SAM stimuli at carriers near the trained frequency. The spectral content of the training stimulus specified spectral and temporal plasticity that may provide a neural substrate for limitations in generalization of temporal discrimination learning.
听觉经验和行为训练可以改变感知表现。然而，时间感知学习对时间和频谱神经处理的影响尚不清楚。具体来说，行为表现中任务泛化所依赖的神经可塑性的属性尚不确定。为了评估行为和神经可塑性之间的关系，我们评估了麻醉猫头鹰猴初级听觉皮层 (AI) 的神经元时间处理和频谱调谐，这些猴子经过训练可以区分包络频率的增加（例如，4-Hz 标准与 >5-Hz 目标）正弦幅度调制 (SAM) 的 1-kHz 或 2-kHz 载波。评估了从 0.5 kHz 到 8 kHz 的载波的行为和神经元性能泛化。心理物理阈值显示出对于从训练载波频率以下一个八度到 ∼0.6 个八度以上的载波具有很高的 SAM 辨别灵敏度。然而，对于训练载波频率以上 >0.6 个八度的载波，SAM 辨别学习的泛化逐渐下降。AI 中的神经反应表明，SAM 辨别训练导致) 时间调制偏好增加，尤其是在接近训练频率的载波附近，) 特征频率接近训练载波频率的神经元的频谱调谐变窄，可能限制了时间训练效果的频谱泛化，以及) 对奖励和非奖励 SAM 频率的放电率对比增强，为接近训练载波频率的行为时间辨别提供了潜在线索。我们的发现表明，在特定的频谱位置进行时间训练可以锐化局部频率调谐，从而将训练效果限制在狭窄的频率范围内，并限制跨更宽频率范围的时间辨别学习的泛化。猴子将幅度调制辨别能力泛化到未训练载波的能力仅限于训练载波频率以下一个八度和 0.6 个八度。不对称的泛化与皮层频谱调谐的锐化以及在接近训练频率的载波处奖励和非奖励 SAM 刺激之间的放电率对比增强相平行。训练刺激的频谱内容指定了频谱和时间可塑性，这可能为时间辨别学习的泛化限制提供了神经基础。
