Baden T, Hedwig B
Department of Zoology, University of Cambridge, Cambridge, United Kingdom.
Dev Neurobiol. 2007 Jan;67(1):68-80. doi: 10.1002/dneu.20323.
Concepts on neuronal signal processing and integration at a cellular and subcellular level are driven by recording techniques and model systems available. The cricket CNS with the omega-1-neurone (ON1) provides a model system for auditory pattern recognition and directional processing. Exploiting ON1's planar structure we simultaneously imaged free intracellular Ca(2+) at both input and output neurites and recorded the membrane potential in vivo during acoustic stimulation. In response to a single sound pulse the rate of Ca(2+) rise followed the onset spike rate of ON1, while the final Ca(2+) level depended on the mean spike rate. Ca(2+) rapidly increased in both dendritic and axonal arborizations and only gradually in the axon and the cell body. Ca(2+) levels were particularly high at the spike-generating zone. Through the activation of a Ca(2+)-sensitive K(+) current this may exhibit a specific control over the cell's electrical response properties. In all cellular compartments presentation of species-specific calling song caused distinct oscillations of the Ca(2+) level in the chirp rhythm, but not the faster syllable rhythm. The Ca(2+)-mediated hyperpolarization of ON1 suppressed background spike activity between chirps, acting as a noise filter. During directional auditory processing, the functional interaction of Ca(2+)-mediated inhibition and contralateral synaptic inhibition was demonstrated. Upon stimulation with different sound frequencies, the dendrites, but not the axonal arborizations, demonstrated a tonotopic response profile. This mirrored the dominance of the species-specific carrier frequency and resulted in spatial filtering of high frequency auditory inputs.
细胞和亚细胞水平上神经元信号处理与整合的概念是由现有的记录技术和模型系统推动的。具有欧米伽-1神经元（ON1）的蟋蟀中枢神经系统为听觉模式识别和方向处理提供了一个模型系统。利用ON1的平面结构，我们同时对输入和输出神经突内的游离细胞内Ca(2+)进行成像，并在体内声刺激期间记录膜电位。响应单个声脉冲时，Ca(2+)上升速率跟随ON1的起始尖峰速率，而最终Ca(2+)水平取决于平均尖峰速率。Ca(2+)在树突和轴突分支中迅速增加，而在轴突和细胞体中仅逐渐增加。Ca(2+)水平在尖峰产生区特别高。通过激活Ca(2+)敏感的K(+)电流，这可能对细胞的电反应特性表现出特定的控制。在所有细胞区室中，特定物种求偶鸣叫的呈现会导致Ca(2+)水平以啁啾节奏出现明显振荡，但不会以更快的音节节奏出现。ON1的Ca(2+)介导的超极化抑制了啁啾之间的背景尖峰活动，起到了噪声滤波器的作用。在定向听觉处理过程中，证明了Ca(2+)介导的抑制和对侧突触抑制之间的功能相互作用。在用不同声频率刺激时，树突而非轴突分支表现出频率调谐响应特征。这反映了特定物种载波频率的主导地位，并导致对高频听觉输入的空间滤波。
