Auditory processing begins by decomposing sounds into their frequency components, raising the question of where the representation of sounds as wholes emerges in the auditory system. To address this question, we used stimulus-specific adaptation (SSA), the reduction in the responses of a neuron to a common sound (standard) which does not generalize to another, rare sound (deviant). SSA to tone frequency has been demonstrated in multiple stations of the auditory pathway, including the inferior colliculus (IC), medial geniculate body (MGB) and auditory cortex. We designed wideband stimuli (tone clouds) that have identical frequency components but are nevertheless distinct. Tone clouds evoked early and substantial SSA in primary auditory cortex (A1) but only late and minor SSA in IC and MGB. These results imply that while in IC and MGB sounds are largely represented in terms of their frequency components, in A1 they are represented as abstract entities.

听觉处理首先将声音分解成它们的频率分量，这就提出了一个问题，即声音作为一个整体的表征出现在听觉系统中的什么位置。为了解决这个问题，我们使用了刺激特异性适应 (SSA)，即减少神经元对普通声音（标准）的反应，这种声音不会泛化到另一种罕见的声音（异常）。SSA 到音调频率已在听觉通路的多个站点中得到证实，包括下丘 (IC)、内侧膝状体 (MGB) 和听觉皮层。我们设计了具有相同频率成分但又截然不同的宽带刺激（音调云）。音调云在初级听觉皮层 (A1) 中引起早期和大量的 SSA，但在 IC 和 MGB 中只有晚期和轻微的 SSA。