Yin Pingbo, Shamma Shihab A, Fritz Jonathan B
Neural Systems Laboratory, Institute for Systems Research, 2207 A.V. Williams Building, University of Maryland, College Park, Maryland 20742, USA.
Neural Systems Laboratory, Institute for Systems Research, Electrical and Computer Engineering Department, 2203 A.V. Williams Building, University of Maryland, College Park, Maryland 20742, USA.
J Acoust Soc Am. 2016 Dec;140(6):4046. doi: 10.1121/1.4968395.
In order to explore the representation of sound features in auditory long-term memory, two groups of ferrets were trained on Go vs Nogo, 3-zone classification tasks. The sound stimuli differed primarily along the spectral and temporal dimensions. In Group 1, two ferrets were trained to (i) classify tones based on their frequency (Tone-task), and subsequently learned to (ii) classify white noise based on its amplitude modulation rate (AM-task). In Group 2, two ferrets were trained to classify tones based on correlated combinations of their frequency and AM rate (AM-Tone task). Both groups of ferrets learned their tasks and were able to generalize performance along the trained spectral (tone frequency) or temporal (AM rate) dimensions. Insights into stimulus representations in memory were gained when the animals were tested with a diverse set of untrained probes that mixed features from the two dimensions. Animals exhibited a complex pattern of responses to the probes reflecting primarily the probes' spectral similarity with the training stimuli, and secondarily the temporal features of the stimuli. These diverse behavioral decisions could be well accounted for by a nearest-neighbor classifier model that relied on a multiscale spectrotemporal cortical representation of the training and probe sounds.
为了探究听觉长期记忆中声音特征的表征，两组雪貂接受了“是”与“否”的三区分类任务训练。声音刺激主要在频谱和时间维度上有所不同。在第一组中，两只雪貂接受训练，（i）根据频率对音调进行分类（音调任务），随后学习（ii）根据白噪声的幅度调制率对其进行分类（调幅任务）。在第二组中，两只雪貂接受训练，根据频率和调幅率的相关组合对音调进行分类（调幅 - 音调任务）。两组雪貂都学会了各自的任务，并能够在训练的频谱（音调频率）或时间（调幅率）维度上推广其表现。当用一组多样的未训练探测刺激对动物进行测试时，这些探测刺激混合了来自两个维度的特征，从而获得了对记忆中刺激表征的深入了解。动物对探测刺激表现出复杂的反应模式，主要反映了探测刺激与训练刺激的频谱相似性，其次反映了刺激的时间特征。这些多样的行为决策可以通过一个最近邻分类器模型得到很好的解释，该模型依赖于训练和探测声音的多尺度频谱 - 时间皮层表征。
