I recall once hearing a talk that discussed, what I recall as, "test patterns" being run across the visual cortex prior to birth. Essentially, waves / patterns of stimulation would go across the optic structure that would be used to, again as I recall it, "calibrate" the visual system.

I dug a bit and was able to find this paper https://pubmed.ncbi.nlm.nih.gov/15289028/ , which seems to track my memory. It has a number of forward and backward citations if you are interested. Perhaps someone with far more than my vague recollection of a talk will step in though!