Atallah Bassam V, Scanziani Massimo
Computational Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA.
Neuron. 2009 May 28;62(4):566-77. doi: 10.1016/j.neuron.2009.04.027.
Neurons recruited for local computations exhibit rhythmic activity at gamma frequencies. The amplitude and frequency of these oscillations are continuously modulated depending on stimulus and behavioral state. This modulation is believed to crucially control information flow across cortical areas. Here we report that in the rat hippocampus gamma oscillation amplitude and frequency vary rapidly, from one cycle to the next. Strikingly, the amplitude of one oscillation predicts the interval to the next. Using in vivo and in vitro whole-cell recordings, we identify the underlying mechanism. We show that cycle-by-cycle fluctuations in amplitude reflect changes in synaptic excitation spanning over an order of magnitude. Despite these rapid variations, synaptic excitation is immediately and proportionally counterbalanced by inhibition. These rapid adjustments in inhibition instantaneously modulate oscillation frequency. So, by rapidly balancing excitation with inhibition, the hippocampal network is able to swiftly modulate gamma oscillations over a wide band of frequencies.
参与局部计算的神经元在伽马频率下呈现节律性活动。这些振荡的幅度和频率会根据刺激和行为状态持续调制。据信这种调制对跨皮质区域的信息流起着关键控制作用。在此我们报告，在大鼠海马体中，伽马振荡的幅度和频率在相邻周期之间快速变化。令人惊讶的是，一次振荡的幅度可预测到下一次振荡的间隔。通过体内和体外全细胞记录，我们确定了其潜在机制。我们表明，幅度的逐周期波动反映了跨越一个数量级的突触兴奋变化。尽管存在这些快速变化，但突触兴奋会立即且成比例地被抑制所平衡。抑制的这些快速调整会瞬间调制振荡频率。因此，通过快速平衡兴奋与抑制，海马体网络能够在很宽的频率范围内迅速调制伽马振荡。
