Laboratory of Sensory Neuroscience and Neuroengineering, Department of Biomedical Engineering, One Brookings Drive, Campus Box 1097, Washington University in St. Louis, St. Louis, MO 63130, USA.
Brain Res. 2010 Mar 10;1319:175-89. doi: 10.1016/j.brainres.2010.01.012. Epub 2010 Jan 14.
Functional imaging can reveal detailed organizational structure in cerebral cortical areas, but neuronal response features and local neural interconnectivity can influence the resulting images, possibly limiting the inferences that can be drawn about neural function. Discerning the fundamental principles of organizational structure in the auditory cortex of multiple species has been somewhat challenging historically both with functional imaging and with electrophysiology. A possible limitation affecting any methodology using pooled neuronal measures may be the relative distribution of response selectivity throughout the population of auditory cortex neurons. One neuronal response type inherited from the cochlea, for example, exhibits a receptive field that increases in size (i.e., decreases in selectivity) at higher stimulus intensities. Even though these neurons appear to represent a minority of auditory cortex neurons, they are likely to contribute disproportionately to the activity detected in functional images, especially if intense sounds are used for stimulation. To evaluate the potential influence of neuronal subpopulations upon functional images of primary auditory cortex, a model array representing cortical neurons was probed with virtual imaging experiments under various assumptions about the local circuit organization. As expected, different neuronal subpopulations were activated preferentially under different stimulus conditions. In fact, stimulus protocols that can preferentially excite selective neurons, resulting in a relatively sparse activation map, have the potential to improve the effective resolution of functional auditory cortical images. These experimental results also make predictions about auditory cortex organization that can be tested with refined functional imaging experiments.
功能成像可以揭示大脑皮质区域的详细组织结构，但神经元反应特征和局部神经互联可能会影响成像结果，从而可能限制对神经功能的推断。从功能成像和电生理学两个方面来看，历史上在多物种听觉皮层中辨别组织结构的基本原理一直具有一定的挑战性。使用神经元总和测量值的任何方法都可能受到影响，其潜在的局限性可能是反应选择性在整个听觉皮层神经元群体中的相对分布。例如，从耳蜗遗传的一种神经元反应类型表现出随刺激强度增加而增大（即选择性降低）的感受野。即使这些神经元似乎代表了听觉皮层神经元的少数群体，但它们很可能不成比例地对功能图像中检测到的活动做出贡献，尤其是如果使用强烈的声音进行刺激。为了评估神经元亚群对初级听觉皮层功能图像的潜在影响，根据局部回路组织的各种假设，使用虚拟成像实验探测代表皮质神经元的模型阵列。正如预期的那样，不同的神经元亚群在不同的刺激条件下优先被激活。事实上，能够优先兴奋选择性神经元的刺激方案会导致相对稀疏的激活图，从而有可能提高功能听觉皮质图像的有效分辨率。这些实验结果还对听觉皮层组织做出了预测，这些预测可以通过改进的功能成像实验进行检验。
