I don't know anything about neuropixels (added that Nature paper to my queue), so don't know if they live up to the hype. That said, the standard tool in many

I don't know anything about neuropixels (added that Nature paper to my queue), so don't know if they live up to the hype. That said, the standard tool in many electrophysiology experiments are still tetrodes and variants (https://en.wikipedia.org/wiki/Tetrode_(biology) https://en.wikipedia.org/wiki/Tetrode_(biology)), which can at best record a few to several cells at a time, within a small radius of the recording tip. Simultaneously recording from hundreds to thousands of cells in multiple brain areas would probably yield quite a bit of valuable data. Also, non-invasive techniques like fMRI (https://en.wikipedia.org/wiki/Functional_magnetic_resonance_imaging https://en.wikipedia.org/wiki/Functional_magnetic_resonance_...) tend to have relatively poor spatial resolution, and track signals that correlate with neural activity (e.g., blood flow) rather than actual electrical activity. Since nearby neurons do not always encode the same information or perform the same function, a spatially-averaged signal isn't going to be as informative.