Stimulus-Selective Response Potentiation persists in adult MMP9−/− mouse V1b. Top: Experimental timeline. Middle: Representative layer 4 VEPs of WT and MMP9−/− mice in response to the initial 200 presentations of visual stimulation at a single orientation (0.05 cpd 100% contrast gratings reversing at 1 Hz), and a familiar and novel stimuli presented 24 h later. Bottom: Mean VEP amplitudes in WT and MMP9−/− mice. Grey bar = mean ± SEM of initial VEP; 24 h later, a significant increase in the VEP amplitude is observed in response to the familiar (left) but not novel (right) stimulus orientation, in both WT and MMP9−/− mice, * p < 0.05, Student’s t-test. n = 6 and 5 subjects for WT and MMP9−/−, respectively.