"ALSO, if there's one thing med school has taught me, it's that one study does not a phenomenon make. (also: spinal cord pathways)."
There's actually a surprising number of studies, all of which have their issues, but converge on the same basic conclusion. The one thing these studies seem to lack is repetition, mostly for understandable logistical reasons. At the bottom here I included a bunch of references I used in the paper I wrote about this last year. The studies can all be found on web of science with an academic subscription.