School of Biological Sciences, Washington State University, 14204 NE Salmon Creek Ave., Vancouver, WA, USA.
J Assoc Res Otolaryngol. 2013 Oct;14(5):719-29. doi: 10.1007/s10162-013-0405-0. Epub 2013 Jul 9.
Perception of complex sounds such as speech is affected by a variety of factors, including attention, expectation of reward, physiological state, and/or disorders, yet the mechanisms underlying this modulation are not well understood. Although dopamine is commonly studied for its role in reward-based learning and in disorders, multiple lines of evidence suggest that dopamine is also involved in modulating auditory processing. In this study, we examined the effects of dopamine application on neuronal response properties in the inferior colliculus (IC) of awake mice. Because the IC contains dopamine receptors and nerve terminals immunoreactive for tyrosine hydroxylase, we predicted that dopamine would modulate auditory responses in the IC. We recorded single-unit responses before, during, and after the iontophoretic application of dopamine using piggyback electrodes. We examined the effects of dopamine on firing rate, timing, and probability of bursting. We found that application of dopamine affected neural responses in a heterogeneous manner. In more than 80 % of the neurons, dopamine either increased (32 %) or decreased (50 %) firing rate, and the effects were similar on spontaneous and sound-evoked activity. Dopamine also either increased or decreased first spike latency and jitter in almost half of the neurons. In 3/28 neurons (11 %), dopamine significantly altered the probability of bursting. The heterogeneous effects of dopamine observed in the IC of awake mice were similar to effects observed in other brain areas. Our findings indicate that dopamine differentially modulates neural activity in the IC and thus may play an important role in auditory processing.
对复杂声音（如语音）的感知受到多种因素的影响，包括注意力、对奖励的期望、生理状态和/或障碍，但这种调节的机制尚不清楚。尽管多巴胺通常因其在基于奖励的学习和障碍中的作用而被研究，但有多项证据表明，多巴胺也参与调节听觉处理。在这项研究中，我们研究了多巴胺应用对清醒小鼠下丘脑中神经元反应特性的影响。由于下丘脑中含有多巴胺受体和酪氨酸羟化酶免疫反应性神经末梢，我们预测多巴胺会调节下丘脑中的听觉反应。我们使用背靠背电极在多巴胺离子电渗应用之前、期间和之后记录单个单位的反应。我们研究了多巴胺对放电率、定时和突发概率的影响。我们发现，多巴胺以异构的方式影响神经反应。在超过 80%的神经元中，多巴胺要么增加（32%）要么减少（50%）放电率，对自发性和声音诱发活动的影响相似。多巴胺还几乎影响了一半神经元的首次尖峰潜伏期和抖动。在 28 个神经元中的 3 个（11%）中，多巴胺显著改变了突发概率。在清醒小鼠下丘脑中观察到的多巴胺的异构效应与在其他脑区观察到的效应相似。我们的发现表明，多巴胺以不同的方式调节下丘脑中的神经元活动，因此可能在听觉处理中发挥重要作用。
