Smotherman Michael, Zhang Shuyi, Metzner Walter
Department of Physiological Science, University of California, Los Angeles, Los Angeles, California 90095-1606, USA.
J Neurosci. 2003 Feb 15;23(4):1464-77. doi: 10.1523/JNEUROSCI.23-04-01464.2003.
Hearing one's own voice is essential for the production of correct vocalization patterns in many birds and mammals, including humans. Bats, for instance, adjust temporal, spectral, and intensity parameters of their echolocation calls by precisely monitoring the characteristics of the returning echo signals. However, neuronal substrates and mechanisms for auditory feedback control of vocalizations are still mostly unknown in any vertebrate. We used echolocating horseshoe bats to investigate the role of the midbrain and hindbrain tegmentum for the control of call frequencies in response to changing auditory feedback. These bats accurately control the frequency of their echolocation calls through auditory feedback both when the bat is at rest [resting frequency (RF)] and when it is flying and compensating for changes in echo frequency caused by flight-induced Doppler shifts [Doppler shift compensation (DSC)]. We iontophoretically injected various GABAergic and glutamatergic transmitter agonists and antagonists into the brainstem tegmentum. We found that within the parabrachial nuclei and the immediately adjacent tegmentum, excitatory effects caused by application of the glutamate agonist AMPA or the GABA(A) antagonist bicuculline raised RF and the frequency of calls emitted during DSC. Bicuculline application routinely blocked DSC altogether. Alternately, inhibitory effects caused by application of either the GABA(A) agonist muscimol or the AMPA antagonist CNQX lowered call frequencies emitted at rest and during DSC. Such an audio-vocal feedback mechanism might share basic aspects with audio-vocal feedback controlling the pitch of vocalizations in other mammals, including the involuntary response to "pitch-shifted feedback" in humans.
听到自己的声音对于包括人类在内的许多鸟类和哺乳动物产生正确的发声模式至关重要。例如，蝙蝠通过精确监测返回的回声信号的特征来调整其回声定位叫声的时间、频谱和强度参数。然而，在任何脊椎动物中，用于发声的听觉反馈控制的神经基质和机制仍然大多未知。我们利用回声定位的马蹄蝠来研究中脑和后脑被盖在响应不断变化的听觉反馈时对叫声频率控制的作用。这些蝙蝠在休息时 [静息频率 (RF)] 以及飞行并补偿由飞行引起的多普勒频移导致的回声频率变化 [多普勒频移补偿 (DSC)] 时，都能通过听觉反馈准确控制其回声定位叫声的频率。我们通过离子电泳将各种GABA能和谷氨酸能递质激动剂和拮抗剂注入脑干被盖。我们发现，在臂旁核及其紧邻的被盖内，应用谷氨酸激动剂AMPA或GABA(A)拮抗剂荷包牡丹碱所引起的兴奋作用会提高RF以及DSC期间发出的叫声频率。应用荷包牡丹碱通常会完全阻断DSC。另外，应用GABA(A)激动剂蝇蕈醇或AMPA拮抗剂CNQX所引起的抑制作用会降低休息时和DSC期间发出的叫声频率。这样一种听觉 - 发声反馈机制可能与控制其他哺乳动物发声音高的听觉 - 发声反馈共享基本方面，包括人类对“音高移位反馈”的非自愿反应。
