> The researchers took samples from brains of humans and rhesus macaque monkeys, separated individual cells and sequenced their RNA. This shows which genes are active (being expressed) in a particular cell and allows researchers to sort them into groups based on gene expression.

Thats (potentially) a lot of neurons to sift through isn't it? I wonder what their process was, or how many neurons they can sift through. Too bad the paywall (yay for greedy journal institutions profiting off the labor of scientists)