Department of Physiology, Anatomy and Genetics, Sherrington Building, Parks Road, Oxford, United Kingdom.
PLoS One. 2011;6(8):e22584. doi: 10.1371/journal.pone.0022584. Epub 2011 Aug 5.
We have previously shown that neurons in primary auditory cortex (A1) of anaesthetized (ketamine/medetomidine) ferrets respond more strongly and reliably to dynamic stimuli whose statistics follow "natural" 1/f dynamics than to stimuli exhibiting pitch and amplitude modulations that are faster (1/f(0.5)) or slower (1/f(2)) than 1/f. To investigate where along the central auditory pathway this 1/f-modulation tuning arises, we have now characterized responses of neurons in the central nucleus of the inferior colliculus (ICC) and the ventral division of the mediate geniculate nucleus of the thalamus (MGV) to 1/f(γ) distributed stimuli with γ varying between 0.5 and 2.8. We found that, while the great majority of neurons recorded from the ICC showed a strong preference for the most rapidly varying (1/f(0.5) distributed) stimuli, responses from MGV neurons did not exhibit marked or systematic preferences for any particular γ exponent. Only in A1 did a majority of neurons respond with higher firing rates to stimuli in which γ takes values near 1. These results indicate that 1/f tuning emerges at forebrain levels of the ascending auditory pathway.
我们之前已经表明，在麻醉（氯胺酮/美托咪定）雪貂的初级听觉皮层（A1）中的神经元对遵循“自然”1/f 动态的动态刺激的反应更强且更可靠，而不是对具有比 1/f 更快（1/f(0.5)）或更慢（1/f(2)）的音调和幅度调制的刺激的反应更强且更可靠。为了研究这种 1/f 调制调谐在听觉通路的哪个部位产生，我们现在描述了下丘中央核（ICC）和丘脑中间膝状体腹侧部分（MGV）中的神经元对 1/f(γ)分布刺激的反应，其中 γ 在 0.5 到 2.8 之间变化。我们发现，虽然从 ICC 记录的大多数神经元对变化最快的（1/f(0.5)分布）刺激表现出强烈的偏好，但 MGV 神经元的反应并没有对任何特定的 γ 指数表现出明显或系统的偏好。只有在 A1 中，大多数神经元对 γ 值接近 1 的刺激以更高的放电率作出反应。这些结果表明，1/f 调谐出现在听觉通路上的前脑水平。
