I find the term fashion a little difficult to wrap my head around, because it's hard to tell the difference between something that's "fashionable" vs "fad" vs "popular" vs "interesting to a lot of people" vs "start of a permanent change in society". Of course I think everyone has trouble differentiating this in the moment....the real difference between these ideas can only really be seen in retrospect (you know, like the internet fad or Dick Rowe saying guitar groups were on their way out).
Anyway, after pondering this, I ran in to this article on fashions in neuroscience.
Essentially, researchers made a faux fMRI map that reflected how often studies were done on various locations in the brain.
Even more interestingly, they also did one that mapped paper impact factor based on various areas to see which areas would be most likely to get further citations. They also did a word cloud.
Red areas got more citations, blue are negative. The top wordle is words in the successful papers, the bottom in the less successful ones (as measured by subsequent citations).
I'm still not sure if they reflects fashion or researchers following the same trains of thought, or just everyone sticking with the areas that light up the best. We'll probably see in about 50 years.
In the mean time, stay classy San Diego.