Kittens were exposed to a periodic grating orientated vertically during the critical period of their life. 2. At the end of the critical period the amplitude of the response to drifting gratings was found to be reduced at the spatial frequency of exposure in multi-unit and in some single unit recordings at lateral geniculate level. 3. The contrast sensitivity measured with behavioural methods also showed a depression at the spatial frequency of exposure. 4. An analysis of the preferred stimulus orientation of cortical units in area 17 showed that all orientations were represented.
