Mehaffey W Hamish, Maler Leonard, Turner Ray W
Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada.
J Neurophysiol. 2008 May;99(5):2641-55. doi: 10.1152/jn.00028.2008. Epub 2008 Mar 26.
The tuning of neuronal responsiveness to specific stimulus frequencies is an important computation across many sensory modalities. The weakly electric fish Apteronotus leptorhynchus detects amplitude modulations of a self-generated quasi-sinusoidal electric organ discharge to sense its environment. These fish have to parse a complicated electrosensory environment with a wide range of possible frequency content. One solution has been to create multiple representations of the sensory input across distinct maps in the electrosensory lateral line lobe (ELL) that participate in distinct behavioral functions. E- and I-type pyramidal cells in the ELL that process sensory input further exhibit a preferred range of stimulus frequencies in relation to the different behaviors and sensory maps. We tested the hypothesis that variations in the intrinsic spiking mechanism of E- and I-type pyramidal cells contribute to map-specific frequency tuning. We find that E-cells exhibit a systematic change in their intrinsic spike characteristics and frequency tuning across sensory maps, whereas I-cells are constant in both spike characteristics and frequency tuning. As frequency tuning becomes more high-pass in E-cells, the refractory variables of spike half-width and afterhyperpolarization magnitude increase, spike threshold increases, adaptation becomes faster, and the gain of the spiking response decreases. These findings indicate that frequency tuning across sensory maps in the ELL is supported by differences in the intrinsic spike characteristics of pyramidal cells, revealing a link between cellular biophysical properties and signal processing in sensory maps with defined behavioral roles.
神经元对特定刺激频率的响应调谐是许多感觉模态中的一种重要计算方式。弱电鱼线翎电鳗通过检测自身产生的准正弦电器官放电的幅度调制来感知周围环境。这些鱼必须解析一个具有广泛可能频率成分的复杂电感觉环境。一种解决方案是在参与不同行为功能的电感觉侧线叶（ELL）中，通过不同的图谱创建感觉输入的多种表征。ELL中处理感觉输入的E型和I型锥体细胞，相对于不同的行为和感觉图谱，进一步表现出偏好的刺激频率范围。我们测试了这样一个假设，即E型和I型锥体细胞内在的放电机制变化有助于图谱特异性的频率调谐。我们发现，E细胞在其内在的放电特征和跨感觉图谱的频率调谐方面表现出系统性变化，而I细胞在放电特征和频率调谐方面均保持不变。随着E细胞的频率调谐变得更加高通，动作电位半宽度和超极化后电位幅度的不应期变量增加，动作电位阈值升高，适应变得更快，并且放电反应的增益降低。这些发现表明，ELL中跨感觉图谱的频率调谐是由锥体细胞内在放电特征的差异所支持的，揭示了细胞生物物理特性与具有明确行为作用的感觉图谱中的信号处理之间的联系。
