Brichta A M, Goldberg J M
Department of Surgery (Otolaryngology-Head and Neck Surgery), Pharmacology and Physiology, University of Chicago, Chicago, Illinois 60637, USA.
J Neurophysiol. 2000 Mar;83(3):1202-23. doi: 10.1152/jn.2000.83.3.1202.
The turtle posterior crista consists of two hemicristae. Each hemicrista extends from the planum semilunatum to the nonsensory torus and includes a central zone (CZ) surrounded by a peripheral zone (PZ). Type I and type II hair cells are found in the CZ and are innervated by calyx, dimorphic and bouton afferents. Only type II hair cells and bouton fibers are found in the PZ. Units were intraaxonally labeled in a half-head preparation. Bouton (B) units could be near the planum (BP), near the torus (BT), or in midportions of a hemicrista, including the PZ and CZ. Discharge properties of B units vary with longitudinal position in a hemicrista but not with morphological features of their peripheral terminations. BP units are regularly discharging and have small gains and small phase leads re angular head velocity. BT units are irregular and have large gains and large phase leads. BM units have intermediate properties. Calyx (C) and dimorphic (D) units have similar discharge properties and were placed into a single calyx-bearing (CD) category. While having an irregular discharge resembling BT units, CD units have gains and phases similar to those of BM units. Rather than any single discharge property, it is the relation between discharge regularity and either gain or phase that makes CD units distinctive. Multivariate statistical formulas were developed to infer a unit's morphological class (B or CD) and longitudinal position solely from its discharge properties. To verify the use of the formulas, discharge properties were compared for units recorded intraaxonally or extracellularly in the half-head or extracellularly in intact animals. Most B units have background rates of 10-30 spikes/s. The CD category was separated into CD-high and CD-low units with background rates above or below 5 spikes/s, respectively. CD-low units have lower gains and phases and are located nearer the planum than CD-high units. In their response dynamics over a frequency range from 0.01-3 Hz, BP units conform to an overdamped torsion-pendulum model. Other units show departures from the model, including high-frequency gain increases and phase leads. The longitudinal gradient in the physiology of turtle B units resembles a similar gradient in the anamniote crista. In many respects, turtle CD units have discharge properties resembling those of calyx-bearing units in the mammalian central zone.
龟的后嵴由两个半嵴组成。每个半嵴从半月平面延伸至无感觉的隆凸，包括一个被外周区（PZ）包围的中央区（CZ）。I型和II型毛细胞存在于中央区，由杯状、二形性和终扣传入神经支配。在外周区仅发现II型毛细胞和终扣纤维。在半脑标本中对神经轴突内进行标记。终扣（B）单位可位于半月平面附近（BP）、隆凸附近（BT）或半嵴的中部，包括外周区和中央区。B单位的放电特性随半嵴中的纵向位置而变化，但不随其外周终末的形态特征而变化。BP单位有规律地放电，增益小，相对于角头速度有小的相位超前。BT单位不规则，增益大，相位超前大。BM单位具有中间特性。杯状（C）和二形性（D）单位具有相似的放电特性，被归为一个含杯状（CD）类别。虽然具有类似于BT单位的不规则放电，但CD单位的增益和相位与BM单位相似。使CD单位与众不同的不是任何单一的放电特性，而是放电规律性与增益或相位之间的关系。开发了多变量统计公式，仅根据单位的放电特性推断其形态类别（B或CD）和纵向位置。为了验证公式的使用，比较了在半脑标本中神经轴突内记录或细胞外记录以及在完整动物中细胞外记录的单位的放电特性。大多数B单位的背景发放率为10 - 30个峰/秒。CD类别分为CD - high和CD - low单位，其背景发放率分别高于或低于5个峰/秒。CD - low单位的增益和相位较低，比CD - high单位更靠近半月平面。在0.01 - 3 Hz频率范围内的反应动力学中，BP单位符合过阻尼扭摆模型。其他单位表现出与该模型的偏差，包括高频增益增加和相位超前。龟B单位生理学中的纵向梯度类似于羊膜动物嵴中的类似梯度。在许多方面，龟CD单位的放电特性类似于哺乳动物中央区含杯状单位的放电特性。
