Knoblich Ulf, Siegle Joshua H, Pritchett Dominique L, Moore Christopher I
McGovern Institute for Brain Research, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology Cambridge, MA, USA.
Front Hum Neurosci. 2010 Oct 21;4:185. doi: 10.3389/fnhum.2010.00185. eCollection 2010.
Gamma oscillations in neocortex are hypothesized to improve information transmission between groups of neurons. We recently showed that optogenetic drive of fast-spiking interneurons (FS) at 40 Hz in mouse neocortex in vivo modulates the spike count and precision of sensory evoked responses. At specific phases of alignment between stimuli and FS activation, total evoked spike count was unchanged compared to baseline, but precision was increased. In the present study, we used computational modeling to investigate the origin of these local transformations, and to make predictions about their impact on downstream signal transmission. We replicated the prior experimental findings, and found that the local gain observed can be explained by mutual inhibition of fast-spiking interneurons, leading to more robust sensory-driven spiking in a brief temporal window post-stimulus, increasing local synchrony. Enhanced spiking in a second neocortical area, without a net increase in overall driven spikes in the first area, resulted from faster depolarization of target neurons due to increased pre-synaptic synchrony. In addition, we found that the precise temporal structure of spiking in the first area impacted the gain between cortical areas. The optimal spike distribution matched the "window of opportunity" defined by the timing of inhibition in the target area: spiking beyond this window did not contribute to downstream spike generation, leading to decreased overall gain. This result predicts that efficient transmission between neocortical areas requires a mechanism to dynamically match the temporal structure of the output of one area to the timing of inhibition in the recipient zone.
新皮层中的伽马振荡被认为可改善神经元群之间的信息传递。我们最近表明，在小鼠新皮层体内以40赫兹对快速放电中间神经元（FS）进行光遗传学驱动，可调节感觉诱发反应的放电计数和精度。在刺激与FS激活之间特定的对齐相位，与基线相比，总诱发放电计数不变，但精度提高。在本研究中，我们使用计算模型来研究这些局部转变的起源，并预测它们对下游信号传递的影响。我们重复了之前的实验结果，发现观察到的局部增益可以通过快速放电中间神经元的相互抑制来解释，这导致在刺激后的短暂时间窗口内感觉驱动的放电更加强劲，增加了局部同步性。由于突触前同步性增加，目标神经元更快去极化，导致第二个新皮层区域的放电增强，而第一个区域的整体驱动放电没有净增加。此外，我们发现第一个区域放电的精确时间结构影响了皮层区域之间的增益。最佳放电分布与目标区域抑制时间定义的“机会窗口”相匹配：超出此窗口的放电对下游放电产生没有贡献，导致整体增益降低。这一结果预测，新皮层区域之间的有效传递需要一种机制，使一个区域输出的时间结构与接受区域的抑制时间动态匹配。
