Metzner W, Koch C, Wessel R, Gabbiani F
Department of Biology, University of California at Riverside, Riverside, California 92521-0427, USA.
J Neurosci. 1998 Mar 15;18(6):2283-300. doi: 10.1523/JNEUROSCI.18-06-02283.1998.
In most sensory systems, higher order central neurons extract those stimulus features from the sensory periphery that are behaviorally relevant (e.g.,Marr, 1982; Heiligenberg, 1991). Recent studies have quantified the time-varying information carried by spike trains of sensory neurons in various systems using stimulus estimation methods (Bialek et al., 1991; Wessel et al., 1996). Here, we address the question of how this information is transferred from the sensory neuron level to higher order neurons across multiple sensory maps by using the electrosensory system in weakly electric fish as a model. To determine how electric field amplitude modulations are temporally encoded and processed at two subsequent stages of the amplitude coding pathway, we recorded the responses of P-type afferents and E- and I-type pyramidal cells in the electrosensory lateral line lobe (ELL) to random distortions of a mimic of the fish's own electric field. Cells in two of the three somatotopically organized ELL maps were studied (centromedial and lateral) (Maler, 1979; Carr and Maler, 1986). Linear and second order nonlinear stimulus estimation methods indicated that in contrast to P-receptor afferents, pyramidal cells did not reliably encode time-varying information about any function of the stimulus obtained by linear filtering and half-wave rectification. Two pattern classifiers were applied to discriminate stimulus waveforms preceding the occurrence or nonoccurrence of pyramidal cell spikes in response to the stimulus. These signal-detection methods revealed that pyramidal cells reliably encoded the presence of upstrokes and downstrokes in random amplitude modulations by short bursts of spikes. Furthermore, among the different cell types in the ELL, I-type pyramidal cells in the centromedial map performed a better pattern-recognition task than those in the lateral map and than E-type pyramidal cells in either map.
在大多数感觉系统中，高阶中枢神经元从感觉外周提取与行为相关的刺激特征（例如，Marr，1982年；Heiligenberg，1991年）。最近的研究使用刺激估计方法量化了各种系统中感觉神经元的尖峰序列所携带的随时间变化的信息（Bialek等人，1991年；Wessel等人，1996年）。在此，我们以弱电鱼的电感觉系统为模型，探讨这种信息如何通过多个感觉图谱从感觉神经元水平传递到高阶神经元。为了确定电场幅度调制在幅度编码通路的两个后续阶段是如何进行时间编码和处理的，我们记录了电感觉侧线叶（ELL）中P型传入神经元以及E型和I型锥体细胞对模拟鱼自身电场的随机失真的反应。研究了三个按躯体定位组织的ELL图谱中的两个图谱中的细胞（中央内侧和外侧）（Maler，1979年；Carr和Maler，1986年）。线性和二阶非线性刺激估计方法表明，与P受体传入神经元不同，锥体细胞不能可靠地编码通过线性滤波和半波整流获得的刺激的任何函数的随时间变化的信息。应用两种模式分类器来区分锥体细胞对刺激做出反应时尖峰出现或未出现之前的刺激波形。这些信号检测方法表明，锥体细胞通过短串尖峰可靠地编码了随机幅度调制中上升和下降的存在。此外，在ELL中的不同细胞类型中，中央内侧图谱中的I型锥体细胞比外侧图谱中的I型锥体细胞以及任一图谱中的E型锥体细胞执行更好的模式识别任务。
