Lee et al. reply

Replying to N. K. Logothetis Nature 468, 10.1038/nature09532 (2010) This is a welcome opportunity to discuss ofMRI, a technology for testing the causal and global impact of defined cell populations in vivo1. The accompanying Comment2 reviews well-known neuroanatomy, but does seem, in its entirety, to be founded on a suggestion that, after experiments were conducted to drive a defined circuit element and measure resulting BOLD signals1, we concluded that no other contributory circuit element was recruited by the driven population. This was not the case, however, as correctly understood by others in the fMRI community3,4,5 and as explained in the paper (for example, “contributions from additional cells and processes downstream of the defined optically triggered population are expected and indeed represent an important aspect of this approach”1). Moreover, the complexity of the brain dictates that such possible contributory mechanisms are more numerous than listed in the Comment2, including many other circuit and feedback mechanisms and classes of cells within neural circuitry6,7,8,9,10. As was discussed1, this is one of the most important and useful aspects of the ofMRI approach. https://www.nature.com/articles/nature09532