Interesting. There are already a few studies about caffeine and the brain-- while drinking caffeine can decrease the chances of dementia, this effect reverses if you drink too much(over 6 cups day)

In the CAIDE study, coffee drinking of 3-5 cups per day at midlife was associated with a decreased risk of dementia/AD by about 65% at late-life. In conclusion, coffee drinking may be associated with a decreased risk of dementia/AD. https://pubmed.ncbi.nlm.nih.gov/20182054/

Conducted at UniSA's Australian Centre for Precision Health at SAHMRI and a team of international researchers*, the study assessed the effects of coffee on the brain among 17,702 UK Biobank participants (aged 37-73), finding that those who drank more than six cups of coffee a day had a 53 per cent increased risk of dementia https://www.eurekalert.org/news-releases/527517