Fasting for the blood draw also revealed a surprising bonus result: "Easily the biggest factor we found in terms of affecting my brain connectivity was whether I had had breakfast and caffeine or not," Poldrack said.
On Tuesdays, when he hadn't drunk his morning joe before the scan, the connectivity within his brain looked very different from his caffeinated brain. Anecdotally, this makes sense. But such an influence had never been observed before. In particular, the connection between the somatosensory motor network and the systems responsible for higher vision grew significantly tighter without caffeine.