Wehr Michael, Zador Anthony M
Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.
Nature. 2003 Nov 27;426(6965):442-6. doi: 10.1038/nature02116.
Neurons in the primary auditory cortex are tuned to the intensity and specific frequencies of sounds, but the synaptic mechanisms underlying this tuning remain uncertain. Inhibition seems to have a functional role in the formation of cortical receptive fields, because stimuli often suppress similar or neighbouring responses, and pharmacological blockade of inhibition broadens tuning curves. Here we use whole-cell recordings in vivo to disentangle the roles of excitatory and inhibitory activity in the tone-evoked responses of single neurons in the auditory cortex. The excitatory and inhibitory receptive fields cover almost exactly the same areas, in contrast to the predictions of classical lateral inhibition models. Thus, although inhibition is typically as strong as excitation, it is not necessary to establish tuning, even in the receptive field surround. However, inhibition and excitation occurred in a precise and stereotyped temporal sequence: an initial barrage of excitatory input was rapidly quenched by inhibition, truncating the spiking response within a few (1-4) milliseconds. Balanced inhibition might thus serve to increase the temporal precision and thereby reduce the randomness of cortical operation, rather than to increase noise as has been proposed previously.
初级听觉皮层中的神经元会对声音的强度和特定频率进行调谐，但这种调谐背后的突触机制仍不明确。抑制作用似乎在皮层感受野的形成中发挥着功能性作用，因为刺激常常会抑制相似或相邻的反应，而且抑制作用的药理学阻断会拓宽调谐曲线。在这里，我们在体内使用全细胞记录来厘清兴奋性和抑制性活动在听觉皮层单个神经元音调诱发反应中的作用。与经典的侧向抑制模型的预测相反，兴奋性和抑制性感受野几乎完全覆盖相同的区域。因此，尽管抑制作用通常与兴奋作用一样强烈，但即使在感受野周围，也没有必要通过抑制来建立调谐。然而，抑制和兴奋以精确且刻板的时间顺序发生：一阵初始的兴奋性输入会迅速被抑制作用消除，在几（1 - 4）毫秒内截断尖峰反应。因此，平衡抑制可能有助于提高时间精度，从而降低皮层运作的随机性，而不是像之前所提出的那样增加噪声。
