Suzuki Mototaka, Larkum Matthew E
NeuroCure Cluster of Excellence, Department of Biology, Humboldt University, Charitéplatz 1, 10117, Berlin, Germany.
Nat Commun. 2017 Aug 17;8(1):276. doi: 10.1038/s41467-017-00282-4.
Cortical surface recording techniques such as EEG and ECoG are widely used for measuring brain activity. The prevailing assumption is that surface potentials primarily reflect synaptic activity, although non-synaptic events may also contribute. Here we show that dendritic calcium spikes occurring in pyramidal neurons (that we showed previously are cognitively relevant) are clearly detectable in cortical surface potentials. To show this we developed an optogenetic, non-synaptic approach to evoke dendritic calcium spikes in vivo. We found that optogenetically evoked calcium spikes were easily detectable and had an unexpected waveform near the cortical surface. Sensory-evoked dendritic calcium spikes were also clearly detectable with amplitudes that matched the contribution of synaptic input. These results reveal how dendritic calcium spikes appear at the cortical surface and their significant impact on surface potentials, suggesting that long-standing surface recording data may contain information about dendritic activity that is relevant to behavior and cognitive function.Surface EEG recordings are thought to primarily detect synaptic activity. Here the authors devise an optogenetic method to evoke dendritic calcium spikes in layer 5 pyramidal cells of the rat somatosensory cortex, and report that optogenetically evoked, as well as sensory-evoked dendritic calcium spikes make a significant contribution to surface EEG recordings.
脑电图（EEG）和皮层脑电图（ECoG）等皮层表面记录技术被广泛用于测量大脑活动。普遍的假设是，表面电位主要反映突触活动，尽管非突触事件也可能有影响。在这里，我们表明，在锥体神经元中发生的树突状钙峰（我们之前表明其与认知相关）在皮层表面电位中清晰可测。为了证明这一点，我们开发了一种光遗传学的、非突触方法来在体内诱发树突状钙峰。我们发现，光遗传学诱发的钙峰很容易检测到，并且在皮层表面附近有一个意想不到的波形。感觉诱发的树突状钙峰也清晰可测，其幅度与突触输入的贡献相匹配。这些结果揭示了树突状钙峰如何出现在皮层表面以及它们对表面电位的重大影响，表明长期的表面记录数据可能包含与行为和认知功能相关的树突状活动信息。表面脑电图记录被认为主要检测突触活动。在这里，作者设计了一种光遗传学方法来诱发大鼠体感皮层第5层锥体细胞中的树突状钙峰，并报告光遗传学诱发的以及感觉诱发的树突状钙峰对表面脑电图记录有重大贡献。
