Optogenetically driven manipulation of circuit-specific activity enables causality studies, but its global brain-wide effect is rarely reported. Here, we applied simultaneous functional magnetic resonance imaging (fMRI) and calcium recording with optogenetic activation of the corpus callosum (CC) connecting barrel cortices (BC). Robust positive BOLD was detected in the ipsilateral BC due to antidromic activity, spreading to the ipsilateral motor cortex (MC), and posterior thalamus (PO). In the orthodromic target, positive BOLD was reliably evoked by 2 Hz light pulses, whereas 40 Hz light pulses led to reduced calcium, indicative of CC-mediated inhibition. This presumed optogenetic CC-mediated inhibition was further elucidated by pairing light pulses with whisker stimulation at varied interstimulus intervals. Whisker-induced positive BOLD and calcium signals were reduced at intervals of 50/100 ms. The calcium-amplitude-modulation-based correlation with whole-brain fMRI signal revealed that the inhibitory effects spread to contralateral BC, ipsilateral MC, and PO. This work raises the need for fMRI to elucidate the brain-wide network activation in response to optogenetic stimulation.

中文翻译：

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通过胼胝体的光遗传学激活绘制全脑网络效应。

光遗传学驱动的对电路特定活动的操纵使因果关系研究成为可能，但很少报道其对大脑的全局影响。在这里，我们应用同步功能磁共振成像 (fMRI) 和钙记录，并通过光遗传学激活连接桶状皮质 (BC) 的胼胝体 (CC)。由于逆向活动，在同侧 BC 中检测到强阳性 BOLD，扩散到同侧运动皮层 (MC) 和后丘脑 (PO)。在顺向靶标中，2 Hz 光脉冲可靠地诱发了正 BOLD，而 40 Hz 光脉冲导致钙减少，表明 CC 介导的抑制。通过将光脉冲与不同刺激间隔的晶须刺激配对，进一步阐明了这种假定的光遗传学 CC 介导的抑制。晶须诱导的正 BOLD 和钙信号以 50/100 毫秒的间隔减少。基于钙幅度调制与全脑 fMRI 信号的相关性表明，抑制作用扩散到对侧 BC、同侧 MC 和 PO。这项工作提出了对 fMRI 的需求，以阐明响应光遗传学刺激的全脑网络激活。