Department of Neurophysiology, Brain Research Institute, Niigata University, 1-757 Asahi-machi, Chuo-ku, Niigata 951-8585, Japan.
Neurosci Res. 2011 Oct;71(2):140-4. doi: 10.1016/j.neures.2011.06.005. Epub 2011 Jun 15.
Natural sounds consist of a component at the fundamental frequency (f0) and its overtones. Pitch is perceived at f0, even when spectral energy at f0 is missing. This missing f0, or 'virtual pitch', is thought to be detected in the auditory cortex and related cortical areas, but the precise neural mechanisms are unknown. One possibility is that virtual pitch can be retrieved from the periodicity of sound waveforms. However, this mechanism requires the temporal accuracy in periodicity detection, and so far the detection of virtual pitch has only been demonstrated at frequencies lower than 1kHz. We investigated the ability of mice to detect virtual pitch up to 5kHz using a two-step sound discrimination test. In the first step of this test, mice were trained to discriminate between tone bursts at 2.5 and 5kHz. In the second step, we tested the ability of mice to discriminate between virtual pitches at 2.5kHz and at 5kHz. It was demonstrated that the performance of mice to discriminate between virtual pitches at 2.5 and 5kHz was significantly affected by previous discrimination learning between tone bursts, indicating that mice can detect virtual pitch up to 5kHz.
自然声音由基频 (f0) 和泛音组成。即使在 f0 处没有光谱能量，也能感知到音高。这种缺失的 f0，或“虚拟音高”，被认为是在听觉皮层和相关的皮质区域中被检测到的，但确切的神经机制尚不清楚。一种可能性是，虚拟音高可以从声音波形的周期性中检索到。然而，这种机制需要在周期性检测方面具有时间准确性，到目前为止，仅在低于 1kHz 的频率下证明了虚拟音高的检测。我们使用两步声音辨别测试来研究小鼠在高达 5kHz 的频率下检测虚拟音高的能力。在该测试的第一步中，训练小鼠辨别 2.5 和 5kHz 的音爆。在第二步中，我们测试了小鼠在 2.5kHz 和 5kHz 之间辨别虚拟音高的能力。结果表明，小鼠在辨别 2.5 和 5kHz 之间的虚拟音高的性能显著受到音爆之间先前辨别学习的影响，表明小鼠可以检测高达 5kHz 的虚拟音高。
