RESPONSE PROPERTIES OF SINGLE UNITS IN THE DORSAL NUCLEUS OF THE LATERAL LEMNISCUS AND PARALEMNISCAL ZONE OF AN ECHOLOCATING BAT
RESPONSE PROPERTIES OF SINGLE UNITS IN THE DORSAL NUCLEUS OF THE LATERAL LEMNISCUS AND PARALEMNISCAL ZONE OF AN ECHOLOCATING BAT
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DOI：
10.1152/jn.1993.69.3.842
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发表时间：
1993-03-01
影响因子：
2.5
通讯作者：
COVEY, E
中科院分区：
文献类型：
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作者：
COVEY, E
1. 相关证据表明，外侧扁豆背核（DNLL）和旁扁豆核（PL）作为双耳分析的中心，位于上橄榄复合体和中脑之间。此外，已知DNLL是中脑抑制性输入的主要来源。本研究的目的是表征回声定位蝙蝠Eptesicus fuscus的DNLL和PL神经元的响应特性，Eptesicus fuscus是一种利用高频听力的物种，可能会有很大比例的神经元对耳间声音水平的差异做出反应。用单耳或双耳对清醒的动物进行听觉刺激，并用玻璃微移液管在细胞外记录单个单元的反应。下丘腹外侧边界下方是含有大量γ -氨基丁酸阳性神经元的区域。根据其免疫组织化学反应性，这整个区域可以考虑为DNLL。然而，在该区域内，双耳反应分布不均匀。尾侧双耳神经元占84%(41/49)，但喙侧仅占29%（6/21）。由于这个原因，吻侧区被认为是一个单独的功能细分，被称为背侧肌旁区（DPL）。PL位于DPL的腹侧，外侧小网膜的中间核和腹侧核的内侧；PL中88%（14/16）的神经元为双耳神经元。当声音单侧呈现时，大多数神经元只对对侧刺激有反应。在DNLL的49个神经元中，42个只对对侧声音有反应，1个只对同侧声音有反应，6个对双耳声音有反应。在DPL中，所有21个神经元都对对侧声音有反应，而对同侧声音没有反应。在PL的16个神经元中，11个只对对侧声音有反应，1个只对同侧声音有反应，4个对双耳声音有反应。当声音同时出现在两只耳朵时，会出现几种不同的双耳互动模式。最常见的模式是一只耳朵对声音的反应被另一只耳朵的声音抑制。在DNLL中，57%（28/49）的神经元表现出这种双耳相互作用。另有10%（5/49）的人在某些层次差异上表现为易化，在其他层次差异上表现为抑制；另有10%（5/49）的人在某些层次差异上表现为易化，但不表现为抑制。在DPL中，观察到的唯一双耳相互作用是一只耳朵对声音的反应被另一只耳朵的声音抑制。在PL中，69%（11/16）的神经元对单耳声音的反应被另一只耳朵的声音抑制，13%（2/16）的神经元在一定的耳间水平差异下表现为促进，但没有抑制。DNLL、DPL和PL神经元的最佳频率分布在大鼠可听范围内。在每个地区，20至30千赫之间的频率范围都有扩大的表示。最小的神经阈值与最小的行为阈值非常匹配。没有发现神经元有异常宽或异常窄的频率调谐。在DNLL、DPL或PL中，几乎没有证据表明有有序的tonotopic进展。相反，具有相似最佳频率的神经元以马赛克模式聚集在一起。DNLL、DPL和PL的大多数神经元自发活动较低。DNLL患者的放电模式为短暂性（39%;16/41）或持续性（58%;24/41）。在DPL中，大多数神经元（76%;16/21）有短暂性反应。在PL中，最常见的放电模式类型是持续型（79%;11/14）。规律性分析显示，DNLL中有12%的神经元（5/41）和DPL中有38%的神经元（8/21）可以被归类为choppers。在对单一刺激的反应中，这三个区域的大多数神经元都具有单调的速率水平功能。当DNLL神经元在BF对音调进行测试时，30%（7/23）的神经元对两个音调中的第二个音调表现出促进反应。虽然这种促进作用在特定的延迟中是最大的，但在第一次刺激后的几十毫秒内也可以看到一些促进作用。这一发现表明，即使在脑干层面，神经元对特定声音的反应也可能受到之前发生的声音的影响。
1. Connectional evidence suggests that the dorsal nucleus of the lateral lemniscus (DNLL) and the paralemniscal one (PL) function as centers for binaural analysis interposed between the superior olivary complex and the midbrain. In addition, the DNLL is known to be a major source of inhibitory input to the midbrain. The aim of this study was to characterize the response properties of neurons in DNLL and PL of the echolocating bat Eptesicus fuscus, a species that utilizes high-frequency hearing and that might be expected to have a large proportion of neurons responsive to interaural differences in sound level.2. Auditory stimuli were presented monaurally or binaurally to awake animals, and responses of single units were recorded extracellularly with the use of glass micropipettes.3. Below the ventrolateral border of the inferior colliculus is a region that contains large gamma-aminobutyric acid-positive neurons. On the basis of its immunohistochemical reactivity, this entire region could be considered as DNLL. However, within the area, there was an uneven distribution of binaural responses. Caudally, binaural neurons made up 84% (41/49) of those tested, but rostrally only 29% (6/21 ). For this reason the rostral area is considered as a separate functional subdivision and referred to as the dorsal paralemniscal zone (DPL). PL is located ventral to DPL and medial to the intermediate and ventral nuclei of the lateral lemniscus; in PL 88% (14/16) of neurons were binaural.4. Most neurons responded only to a contralateral stimulus when sounds were presented monaurally. Out of 49 neurons in DNLL, 42 responded only to a contralateral sound, 1 responded only to an ipsilateral sound, and 6 responded to sound at either ear. In the DPL, all of the 21 neurons tested responded to a contralateral sound and none to an ipsilateral sound. Out of 16 neurons in the PL, 11 responded only to a contralateral sound, 1 responded only to an ipsilateral sound, and 4 responded to sound at either ear.5. When sounds were presented at both ears simultaneously, several different patterns of binaural interaction occurred. The most common pattern was suppression of the response to sound at one ear by sound at the other ear. In DNLL, 57% (28/49) of neurons showed this type of binaural interaction. Another 10% (5/49) showed facilitation at some interaural level differences and suppression at others, and another 10% (5/49) showed facilitation at some interaural level differences but no suppression. In DPL the only binaural interaction seen was suppression of the response to sound at one ear by sound at the other ear. In PL, 69% (11/16) of neurons showed suppression of the response to sound at one ear by sound at the other ear, and 13% (2/16) showed facilitation at certain interaural level differences but no suppression.6. Best frequencies of neurons in DNLL, DPL, and PL were distributed throughout the range audible to Eptesicus. In each area, there was an expanded representation of the frequency range between 20 and 30 kHz. The minimum neural thresholds closely matched the minimum behavioral thresholds that have been measured for Eptesicus. No neurons were found to have unusually broad or unusually narrow frequency tuning.7. There was little evidence of an orderly tonotopic progression in DNLL, DPL, or PL. Instead, neurons with similar best frequencies were clustered together in a mosaic pattern.8. Most neurons in DNLL, DPL, and PL had low spontaneous activity. Discharge patterns in DNLL were either transient (39%; 16/41) or sustained (58%; 24/41). In DPL the majority of neurons (76%; 16/21) responded transiently. In PL, the most common type of discharge pattern was the sustained type (79%; 11/14). Regularity analysis showed that 12% of neurons in DNLL (5/41) and 38% of neurons in DPL (8/21 ) could be classified as choppers. In response to monaural stimuli, the majority of neurons in all three areas had monotonic rate-level functions.9. When DNLL neurons were tested with pairs of tones at BF, 30% (7/23) showed a facilitated response to the second of the two tones. Although the facilitation was greatest at certain delays, some facilitation was seen over a period lasting several tens of milliseconds after the first stimulus. This finding suggests that, even at the level of the brain stem, the response of a neuron to a given sound may be influenced by sounds that have occurred previously.