Representation of individual elements of a complex call sequence in primary auditory cortex.
Representation of individual elements of a complex call sequence in primary auditory cortex.
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DOI：
10.3389/fnsys.2013.00072
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发表时间：
2013
影响因子：
3
通讯作者：
Palmer AR
中科院分区：
文献类型：
--
作者：
Wallace MN;Grimsley JM;Anderson LA;Palmer AR
同种通信呼叫可以是有节奏的，或者包含由短暂的静默期隔开的恒定或调频的谐音和噪声突发的延长的、不连续的序列。在豚鼠中，有节奏的叫声可以在初级听觉皮质(AI)内产生同构的反应，在那里单个单位对每个叫声元素做出反应。其他叫声，如Chutter，由一系列短而不规则的音节组成，这些音节的光谱内容各不相同，更像是人类的语音。这些叫声也可以唤起同构的反应，但可能只在听觉带的领域这样做，而不是在人工智能中。在这里，我们提出了证据，即人工智能中的细胞将音节中的单个元素视为单独的听觉对象，并选择性地对它们中的一个或一个子集做出反应。我们用单个Chutter样本比较了氨基甲酸酯麻醉豚鼠AI-AI的低频部分(LF)和丘脑内侧膝状体的低频部分-MGB(LF)的单/多单位反应。丘脑和大脑皮层细胞对Chutter Call中存在的8个主要元素中的一个或多个的放电率都有短暂的增加。几乎没有一个单位对所有8个元素都有反应。虽然对其中一到五种元素有许多不同的反应组合，但MBG(LF)和AI(LF)神经元表现出相同的特定类型的反应组合。大脑皮层上层附近的单位倾向于对类似的元素组合做出反应，而深层的反应较弱。因此，需要将来自多个人工智能单元的响应组合在一起，以表示整个Chutter呼叫。我们的结果并不排除建设性收敛的可能性，但没有证据表明人工智能内部的投入融合导致了所有八个元素的完整表示。
Conspecific communication calls can be rhythmic or contain extended, discontinuous series of either constant or frequency modulated harmonic tones and noise bursts separated by brief periods of silence. In the guinea pig, rhythmic calls can produce isomorphic responses within the primary auditory cortex (AI) where single units respond to every call element. Other calls such as the chutter comprise a series of short irregular syllables that vary in their spectral content and are more like human speech. These calls can also evoke isomorphic responses, but may only do so in fields in the auditory belt and not in AI. Here we present evidence that cells in AI treat the individual elements within a syllable as separate auditory objects and respond selectively to one or a subset of them. We used a single chutter exemplar to compare single/multi-unit responses in the low-frequency portion of AI—AI(LF) and the low-frequency part of the thalamic medial geniculate body—MGB(LF) in urethane anaesthetized guinea pigs. Both thalamic and cortical cells responded with brief increases in firing rate to one, or more, of the 8 main elements present in the chutter call. Almost none of the units responded to all 8 elements. While there were many different combinations of responses to between one and five of the elements, MBG(LF) and AI(LF) neurons exhibited the same specific types of response combinations. Nearby units in the upper layers of the cortex tended to respond to similar combinations of elements while the deep layers were less responsive. Thus, the responses from a number of AI units would need to be combined in order to represent the entire chutter call. Our results don't rule out the possibility of constructive convergence but there was no evidence that a convergence of inputs within AI led to a complete representation of all eight elements.