CORTICAL REPRESENTATION OF AUDITORY SPACE

拟议研究的目标是确定具体要素， 听觉系统用来识别 一个声源，并探索声音定位的皮层代码。的 外耳的方向传递函数形成了 声音，从而提供线索的垂直和前/后的位置， 声音.在刺激频谱中引入的尖锐或凹口导致 空间错觉，这是明显的系统性错误定位。 人类行为实验，结合计算模型， 将分离频谱峰值和陷波的特定基本费用 (e.g.,能量最大值或最小值、光谱斜率、斜率的快速变化）。 这种方法将限制神经元模型的定位 机制等 几个小组的不懈努力未能找到一张地形图 大脑皮层的听觉空间，至少不是传统意义上的 一组神经元，其空间调谐作为皮层的函数而变化， 地方然而，该实验室最近的结果表明， 在猫的大脑中， 前外侧裂区（AES区）可以编码声音的方位角 源头拟议中的猫神经生理学实验将比较 在区域AES、A1和A2中进行位置划分。实验将集中在 是特定的神经元本身编码定位，还是它们 仅仅对特定的定位线索敏感。为了实现这一目标， 声源仰角的编码将受到特别关注。 其他的神经生理学实验将探索 人类听者的行为和猫皮层的生理学 神经元人类的定位行为容忍相当大的变化， 源光谱的形状，但当光谱包含尖峰时失败 或缺口。皮层神经元对刺激位置的时间编码 可以用光谱形状不同的刺激进行测试。的程度 特定的皮层神经元构成了声音的基质 定位，人们可能会期望皮层位置编码成功， 在类似于人类行为的条件下失败。 听觉皮层是颞叶的一个关键部分， 许多沟通过程的皮质基底，是一个共同的网站， 癫痫灶，并可参与精神分裂症。拟议 神经生理学实验解决了感觉的基本问题， 大脑皮层中的编码，位置编码和时间编码的问题。 频谱形状实验探索了基本的声音定位机制 并且，通过测试大脑皮层的切割和行为之间的相似性， 提供了一个测试的行为意义的皮层颞叶 编码结果。理解基本的皮层编码机制 应该有助于颞叶病理学的评价， 设计对损伤和疾病的治疗反应。

The objectives of the proposed research are to identify specific elements of sound spectra that the auditory system uses to identify the location of a sound source and to explore the cortical code for sound location. The directional transfer functions of the external ears shape the spectra of sounds, thereby providing cues to the vertical and front/back locations of sounds. Sharp or notches introduced into a stimulus spectrum result in spatial illusions, which are evident as systematic mis-localizations. Behavioral experiments in humans, combined with computational modelling, will dissociate specific elementary fares of spectral peaks and notches (e.g., energy maxima or minima, spectral slopes, rapid changes in slopes). This approach will place constraints on neuronal models of localization mechanisms. Determined efforts by several groups have failed to find a topographic map of auditory space in the cortex, at least not in the conventional sense of an array of neurons that vary in spatial tuning as a function of cortical place. Recent results from this laboratory, however, have demonstrated that the temporal firing patterns of single auditory neurons in the cat's anterior ectosylvian area (area AES) can code the azimuth of a sound source. Proposed neurophysiological experiments in cats will compare location ceding in areas AES, A1, and A2. Experiments will focus on whether particular neurons code localization per se, or whether they merely are sensitive to particular localization cues. Toward that goal, the coding of sound source elevation will receive particular attention. Additional neurophysiological experiments will explore parallels between the behavior of human listeners and the physiology of cat cortical neurons. Human localization behavior tolerates considerable variability in the shapes of source spectra, but fails when spectra contain sharp peaks or notches. Temporal coding of stimulus locations by cortical neurons will be tested with stimuli that vary in spectral shape. To the degree that particular cortical neurons form part of the substrate for sound localization, one might expect cortical location coding to succeed and fail under conditions analogous to those observed in human behavior. The auditory cortex is a key element of the temporal lobe, which is the cortical substrate for many communicative processes, is a common site of epileptic foci, and can be involved in schizophrenia. The proposed neurophysiological experiments address a fundamental issue of sensory coding in the cortex, the issue of place coding versus temporal coding. The spectral shape experiments explore basic sound localization mechanisms and, by testing for parallels between cortical ceding and behavior, provide a test of the behavioral significance of the cortical temporal coding results. An understanding of basic cortical coding mechanisms should contribute to the valuation of temporal lobe pathology and the design of therapeutic responses to injury and disease.