Dynamics of precise spike timing in primary auditory cortex
Dynamics of precise spike timing in primary auditory cortex
复制标题
DOI：
10.1523/jneurosci.3825-03.2004
复制
发表时间：
2004-02-04
影响因子：
5.3
通讯作者：
Shamma, SA
中科院分区：
文献类型：
--
作者：
Elhilali, M;Fritz, JB;Shamma, SA
尽管初级听觉皮层 (A1) 中的单个单元在对声音出现的相位响应中表现出精确的计时（精确度为几毫秒），但矛盾的是，它们无法维持对频率远远超过 20 Hz 的重复刺激的同步响应。为了探索皮质反应这两个方面之间的关系，我们设计了一种宽带刺激，其缓慢调制的频谱时间包络位于快速调制的波形（或精细结构）之上。利用这种刺激，我们量化了皮质细胞独立且同时编码刺激包络和精细结构的能力。具体来说，通过将单位响应与这两个刺激维度反向关联，我们测量了与包络、精细结构和完整刺激处理相关的谱时响应场 (STRF)。 A1 细胞对慢光谱时间包膜反应良好，并产生多种 STRF。在超过 70% 的情况下，A1 单元还可以在整个刺激过程中精确跟踪精细结构调制，频率高达数百赫兹。然而，这种双重响应取决于细胞受到快速和慢速调制的驱动，因为对缓慢调制包络线的响应控制了精细结构的表达。我们还证明，突触抑制和促进的简化模型和/或丘脑兴奋和皮质抑制的皮质网络可以解释观察到的结果的主要趋势。最后，我们讨论这些共存、互补的动态响应模式的潜在功能意义和感知相关性。
Although single units in primary auditory cortex (A1) exhibit accurate timing in their phasic response to the onset of sound (precision of a few milliseconds), paradoxically, they are unable to sustain synchronized responses to repeated stimuli at rates much beyond 20 Hz. To explore the relationship between these two aspects of cortical response, we designed a broadband stimulus with a slowly modulated spectrotemporal envelope riding on top of a rapidly modulated waveform (or fine structure). Using this stimulus, we quantified the ability of cortical cells to encode independently and simultaneously the stimulus envelope and fine structure. Specifically, by reverse-correlating unit responses with these two stimulus dimensions, we measured the spectrotemporal response fields (STRFs) associated with the processing of the envelope, the fine structure, and the complete stimulus. A1 cells respond well to the slow spectrotemporal envelopes and produce a wide variety of STRFs. In over 70% of cases, A1 units also track the fine-structure modulations precisely, throughout the stimulus, and for frequencies up to several hundred Hertz. Such a dual response, however, is contingent on the cell being driven by both fast and slow modulations, in that the response to the slowly modulated envelope gates the expression of the fine structure. We also demonstrate that either a simplified model of synaptic depression and facilitation, and/or a cortical network of thalamic excitation and cortical inhibition can account for major trends in the observed findings. Finally, we discuss the potential functional significance and perceptual relevance of these coexistent, complementary dynamic response modes.