INTERACTION OF EXCITATION AND INHIBITION IN PROCESSING OF PURE-TONE AND AMPLITUDE-MODULATED STIMULI IN THE MEDIAL SUPERIOR OLIVE OF THE MOUSTACHED BAT
INTERACTION OF EXCITATION AND INHIBITION IN PROCESSING OF PURE-TONE AND AMPLITUDE-MODULATED STIMULI IN THE MEDIAL SUPERIOR OLIVE OF THE MOUSTACHED BAT
复制标题
DOI：
10.1152/jn.1994.71.2.706
复制
发表时间：
1994-02-01
影响因子：
2.5
通讯作者：
GROTHE, B
中科院分区：
文献类型：
--
作者：
GROTHE, B
1. 在具有良好低频听力的哺乳动物中，内侧上橄榄核 (MSG) 处理耳间时间或相位差，这是声音定位的重要线索。它的细胞接收来自两个耳蜗核的兴奋性投射，并被认为具有重合探测器的功能。大多数哺乳动物的 MSO 神经元的反应模式主要是持续的。相比之下，小胡子蝙蝠的 MSO 是一个单耳核，含有具有阶段性放电模式的神经元。这些神经元接收来自对侧耳蜗前腹核 (AVCN) 和同侧梯形体内侧核 (MNTB) 的投射。 2. 为了进一步研究 MSO 在蝙蝠中的作用，记录了 MSO 中 252 个单个单元对纯音和正弦调幅 (SAM) 刺激的反应。结果证实，小胡子蝙蝠的 MSO 是按音调组织的，背部频率较低，腹侧频率较高。 61kHz 区域的比例过高。大多数测试的神经元（88%）是单耳神经元，仅对对侧刺激作出反应。他们的反应不会受到同侧耳朵刺激的影响。 3. 所有 MSO 神经元中只有 11% 是自发活动的。在这些神经元中，刺激呈现期间自发放电率受到抑制。 4. 大多数细胞 (85%) 的反应为阶段性放电模式。大约一半（51%）的人做出了与水平无关的阶段性 ON 反应。其他相位响应模式包括相位关闭或相位开-关，具体取决于刺激频率。具有开关放电模式的神经元在 61kHz 区域最常见，而在高频区域不存在。 5.双音实验表明，在短音间间隔时，对第二个刺激的ON反应或对第一个刺激的OFF反应被抑制。 6. 在神经药理学实验中，将甘氨酸应用于 MSO 神经元 (n = 71) 会抑制任何音调诱发的反应。在甘氨酸拮抗剂士的宁存在的情况下，反应模式从阶段性变为持续性（n = 35），并且神经元对双音实验中呈现的两种音调做出反应，与音间间隔无关（n = 5）。士的宁的作用是可逆的。 7. 用正弦调幅 (SAM) 信号测试的 21 个神经元中的 20 个表现出低通或带通滤波器特性。 SAM 信号测试还显示，在测试的 21 个细胞中，有 13 个细胞的抑制时间总和较弱。 9. 在所有六个测试的神经元中，士的宁的应用将 SAM 滤波器上限转移到更高的调制频率。响应的下限截止频率保持不变。 10. 结论是，直接兴奋性、初级类 AVCN 输入和通过 MNTB 的间接甘氨酸抑制输入的单耳相互作用的时间决定了 MSO 神经元的反应，以创建阶段性 ON 或阶段性 OFF 放电模式。这种与时间相关的相互作用可能在飞行昆虫翅膀拍动引起的振幅调制的处理中发挥作用。
1. In mammals with good low-frequency hearing, the medial superior olive (MSG) processes interaural time or phase differences that are important cues for sound localization. Its cells receive excitatory projections from both cochlear nuclei and are thought to function as coincidence detectors. The response patterns of MSO neurons in most mammals are predominantly sustained. In contrast, the MSO in the mustached bat is a monaural nucleus containing neurons with phasic discharge patterns. These neurons receive projections from the contralateral anteroventral cochlear nucleus (AVCN) and the ipsilateral medial nucleus of the trapezoid body (MNTB). 2. To further investigate the role of the MSO in the bat, the responses of 252 single units in the MSO to pure tones and sinusoidal amplitude-modulated (SAM) stimuli were recorded. The results confirmed that the MSO in the mustached bat is tonotopically organized, with low frequencies in the dorsal part and high frequencies in the ventral part. The 61-kHz region is overrepresented. Most neurons tested (88%) were monaural and discharged only in response to contralateral stimuli. Their response could not be influenced by stimulation of the ipsilateral ear. 3. Only 11% of all MSO neurons were spontaneously active. In these neurons the spontaneous discharge rate was suppressed during the stimulus presentation. 4. The majority of cells (85%) responded with a phasic discharge pattern. About one-half(51%) responded with a level-independent phasic ON response. Other phasic response patterns included phasic OFF or phasic ON-OFF, depending on the stimulus frequency. Neurons with ON-OFF discharge patterns were most common in the 61-kHz region and absent in the high-frequency region. 5. Double tone experiments showed that at short intertone intervals the ON response to the second stimulus or the OFF response to the first stimulus was inhibited. 6. In neuropharmacological experiments, glycine applied to MSO neurons (n = 71) inhibited any tone-evoked response. In the presence of the glycine antagonist strychnine the response patterns changed from phasic to sustained (n = 35) and the neurons responded to both tones presented in double tone experiments independent of the intertone interval (n = 5). The effects of strychnine were reversible. 7. Twenty of 21 neurons tested with sinusoidally amplitude-modulated (SAM) signals exhibited low-pass or band-pass filter characteristics. Tests with SAM signals also revealed a weak temporal summation of inhibition in 13 of the 21 cells tested. 9. Application of strychnine shifted the upper SAM filter limits to higher modulation frequencies in all six neurons tested. The lower cutoff frequency of the response remained unchanged. 10. It is concluded that the timing of the monaural interaction of the direct excitatory, primary-like AVCN input and the indirect glycinergic inhibitory input via the MNTB shapes the responses of MSO neurons to create either phasic ON or phasic OFF discharge patterns. This time-dependent interaction may play a role in the processing of amplitude modulations caused by wing beats of flying insects.