Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Eur J Neurosci. 2010 Jul;32(1):155-64. doi: 10.1111/j.1460-9568.2010.07280.x. Epub 2010 Jun 28.
During the early postnatal development of rats, the structural and functional maturation of the central auditory nuclei strongly relies on the natural character of the incoming neural activity. Even a temporary deprivation in the critical period results in a deterioration of neuronal responsiveness in adult animals. We demonstrate that besides the poorer frequency selectivity of neurons in the impaired animals reported previously [Grecova et al. (2009)Eur. J. Neurosci. 29, 1921-1930], the neuronal representation of sound intensity is significantly affected. Rate-intensity functions of inferior colliculus neurons were recorded in anaesthetized adult rats that were exposed to intense noise at postnatal day 14, and compared with those obtained in age-matched controls. Although the response thresholds were similar in the exposed and control rats, the neurons in the exposed animals had a longer first-spike latency, a narrower dynamic range, lower maximum response magnitudes and a steeper slope of the rate-intensity functions. The percentage of monotonic neurons was significantly lower in the exposed animals. The observed anomalies were confined to the mid- and high-frequency regions, whereas no significant changes were found in the low-frequency neurons. The altered parameters of the individual rate-intensity functions led also to differences in the cumulative responses. We conclude that a brief noise exposure during the critical period leads to a frequency-dependent alteration of the sound intensity representation in the inferior colliculus of adult rats. The results suggest that such impairments may appear in individuals with normal hearing thresholds, but with a history of noise exposure very early in childhood.
在大鼠出生后的早期发育过程中，中枢听觉核的结构和功能成熟强烈依赖于传入神经活动的自然特性。即使在关键期内短暂剥夺，也会导致成年动物神经元反应性恶化。我们证明，除了先前报道的受损动物神经元频率选择性较差[Grecova 等人（2009 年）Eur. J. Neurosci. 29, 1921-1930]之外，神经元对声音强度的表示也受到显著影响。在出生后第 14 天暴露于强噪声的麻醉成年大鼠中记录了下丘神经元的率-强度函数，并与年龄匹配的对照组进行了比较。尽管暴露组和对照组的反应阈值相似，但暴露组的神经元具有更长的第一峰潜伏期、更窄的动态范围、更低的最大反应幅度和更陡的率-强度函数斜率。暴露组中单调神经元的百分比显著降低。观察到的异常仅限于中高频区，而低频神经元没有发现明显变化。个体率-强度函数的改变参数也导致累积反应的差异。我们得出结论，在关键期内短暂的噪声暴露会导致成年大鼠下丘声音强度表示的频率依赖性改变。结果表明，在有正常听力阈值但有儿童早期噪声暴露史的个体中可能会出现这种损伤。
