Instructive changes in the kitten's visual cortex and their limitation.

Kittens were reared wearing masks that contained strong cylindrical lenses, which allowed them to see only contours of one orientation. Selective exposure was alternated between the two eyes on successive days, while each time the other eye was covered by the mask. The total duration of exposure was different in the two eyes, amounting to 50 h for one eye and at least 100 h for the other. This resulted in asymmetric distributions of ocular dominance: neurones preferring precisely the experienced orientation favoured the eye with longer exposure, whereas neurones preferring oblique orientations adjacent to the experienced one surprisingly were dominated by the eye with shorter exposure. Thus neurones originally belonging to this group and dominated by the longer exposed eye must have tuned their orientation preference to the experienced orientation as a result of the longer exposure. Such instructive changes seem to be limited by the original response borders of the cortical neurones, as predicted by Hebb's rules for synaptic plasticity.