Long-lasting modulation by stimulus context in primate auditory cortex
Long-lasting modulation by stimulus context in primate auditory cortex
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DOI：
10.1152/jn.01124.2004
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发表时间：
2005-07-01
影响因子：
2.5
通讯作者：
Wang, XQ
中科院分区：
文献类型：
--
作者：
Bartlett, EL;Wang, XQ
嵌入到声学流中的声音不能在不参考其刺激上下文的情况下被明确地分割和识别。为了了解刺激背景在皮层处理中的作用，我们研究了觉醒的绒猴听皮层神经元对两声序列的反应，重点是除了载波频率之外的刺激特性。通过使用调制音调和噪声刺激的组合，观察到皮层反应的抑制和易化调制。主要研究结果如下。1)前刺激可在持续时间内抑制或促进对后继刺激的反应S。这些长期效应除取决于载波频率外，还取决于前一刺激的持续时间、声级和调制参数。无论这两个刺激是否被静默间隔分开，它们都会发生。2)抑制通常是这样调整的，即参数与后续刺激相似的前一刺激产生最强的抑制。然而，即使在两种刺激不同的情况下，许多单位的反应也可以被抑制，尽管通常较弱。在某些情况下，只有不同的前一刺激在对后一刺激的反应中产生抑制。3)与抑制相反，当两个刺激不同时，前一个刺激对后续刺激反应的促进作用通常最强。4)前一次刺激诱发的放电频率与后一次刺激诱发的放电频率变化之间没有明显的相关性，表明所观察到的抑制并非简单的习惯化或棘波适应的结果。这些结果表明，听觉皮质神经元对给定刺激的反应可以由先前的刺激诱导出持续的调制。对后续刺激的反应的减少或增加取决于前一刺激的光谱、时间和强度特性。这表明皮层对声音的听觉反应不是静态的，而是以一种特定于刺激的方式依赖于刺激环境。刺激背景的长期影响和易化的流行表明，这种皮层反应特性对于前向掩蔽以外的听觉加工非常重要，例如对于听觉分流和分离。
A sound embedded in an acoustic stream cannot be unambiguously segmented and identified without reference to its stimulus context. To understand the role of stimulus context in cortical processing, we investigated the responses of auditory cortical neurons to 2-sound sequences in awake marmosets, with a focus on stimulus properties other than carrier frequency. Both suppressive and facilitatory modulations of cortical responses were observed by using combinations of modulated tone and noise stimuli. The main findings are as follows. 1) Preceding stimuli could suppress or facilitate responses to succeeding stimuli for durations >1 s. These long-lasting effects were dependent on the duration, sound level, and modulation parameters of the preceding stimulus, in addition to the carrier frequency. They occurred regardless of whether the 2 stimuli were separated by a silent interval. 2) Suppression was often tuned such that preceding stimuli whose parameters were similar to succeeding stimuli produced the strongest suppression. However, the responses of many units could be suppressed, although often weaker, even when the 2 stimuli were dissimilar. In some cases, only a dissimilar preceding stimulus produced suppression in the responses to the succeeding stimulus. 3) In contrast to suppression, facilitation of responses to succeeding stimuli by the preceding stimulus was usually strongest when the 2 stimuli were dissimilar. 4) There was no clear correlation between the firing rate evoked by the preceding stimulus and the change in the firing rate evoked by the succeeding stimulus, indicating that the observed suppression was not simply a result of habituation or spike adaptation. These results demonstrate that persistent modulations of the responses of an auditory cortical neuron to a given stimulus can be induced by preceding stimuli. Decreases or increases of responses to the succeeding stimuli are dependent on the spectral, temporal, and intensity properties of the preceding stimulus. This indicates that cortical auditory responses to a sound are not static, but instead depend on the stimulus context in a stimulus-specific manner. The long-lasting impact of stimulus context and the prevalence of facilitation suggest that such cortical response properties are important for auditory processing beyond forward masking, such as for auditory streaming and segregation.