Karmarkar Uma R, Buonomano Dean V
Departments of Neurobiology and Psychology, and the Brain Research Institute, University of California, Los Angeles, Los Angeles, California 90095 USA.
Learn Mem. 2003 Mar-Apr;10(2):141-7. doi: 10.1101/lm.55503.
Although temporal processing is used in a wide range of sensory and motor tasks, there is little evidence as to whether a single centralized clock or a distributed system underlies timing in the range of tens to hundreds of milliseconds. We investigated this question by studying whether learning on an auditory interval discrimination task generalizes across stimulus types, intervals, and frequencies. The degree to which improvements in timing carry over to different stimulus features constrains the neural mechanisms underlying timing. Human subjects trained on a 100- or 200-msec interval discrimination task showed an improvement in temporal resolution. This learning generalized to a perceptually distinct duration stimulus, as well as to the trained interval presented with tones at untrained spectral frequencies. The improvement in performance did not generalize to untrained intervals. To determine if spectral generalization was dependent on the importance of frequency information in the task, subjects were simultaneously trained on two different intervals identified by frequency. As a whole, our results indicate that the brain uses circuits that are dedicated to specific time spans, and that each circuit processes stimuli across nontemporal stimulus features. The patterns of generalization additionally indicate that temporal learning does not rely on changes in early, subcortical processing, because the nontemporal features are encoded by different channels at early stages.
尽管时间处理在广泛的感觉和运动任务中都有应用，但对于在几十到几百毫秒范围内的计时是基于单个集中式时钟还是分布式系统，几乎没有证据。我们通过研究在听觉间隔辨别任务上的学习是否能推广到不同的刺激类型、间隔和频率来探讨这个问题。计时改善推广到不同刺激特征的程度限制了计时背后的神经机制。在100毫秒或200毫秒间隔辨别任务上接受训练的人类受试者在时间分辨率上有了提高。这种学习推广到了在感知上不同的持续时间刺激，以及在未训练的频谱频率下呈现的训练间隔的音调。表现的改善并没有推广到未训练的间隔。为了确定频谱推广是否依赖于任务中频率信息的重要性，受试者同时在由频率识别的两个不同间隔上进行训练。总体而言，我们的结果表明大脑使用专门用于特定时间跨度的回路，并且每个回路跨非时间刺激特征处理刺激。推广模式还表明时间学习不依赖于早期皮层下处理的变化，因为非时间特征在早期由不同通道编码。
