Psychedelics alter more neurons than expected

I started reading two recent neuroscience books (elusive cures and natural neuroscience) that while have different goals both highlight the utility of systems neuroscience. In elusive cures the author presented a brief history of the evolving ideological currents where neuroscientists first only cared about about the specific brain region where a stimulus or disorder is happening (first-order effects), then decades later realised the importance of downstream and upstream brain regions (second-order), and are finally coming to terms that the brain is a complex system with coupled regions (third-order).

Seems the article is a contemporary example of the first->second-order realisation...

“This was a very unexpected finding given the current assumptions about how psychedelic medicine works”

"Surprisingly, psychedelic treatment was still able to strongly boost connectivity onto these neurons”

Knowing (those types of) psychedelics bind to serotonin receptors scientists studied neurons with such receptors and didn't focus on the others. Their study looked at other neurons and found plasticity changes there too.