Representative experiments of animals in all four age groups studied (PD25, PD95, PD130 and PD215) are displayed. Optical imaging maps of responses to the ipsi- and contralateral eye in the binocular region of mouse visual cortex in both control animals (left column: a, c, e, g) and monocularly deprived animals (right column: b, d, f, h) are shown. Both colour-coded polar maps of retinotopy (top) and grey-scale coded response magnitude maps (below) are illustrated. For each experiment, the histogram of ocular dominance scores, the average ocular dominance index (ODI) and the corresponding 2-D ocular dominance maps (ODI values colour-coded according to the scheme shown in the lower right corner of the figure: blue represents negative, red positive values) is included. Note that in control animals of all ages, activity patches evoked by the stimulation of the contralateral eye were consistently darker than those after stimulation of the ipsilateral eye (a, c, e, g) and that 2-D ocular dominance maps are red and yellow indicating contralateral dominance. In contrast, monocular deprivation for 4 days in PD25 animals (b) or for 7 days in PD95 animals (d) induced a significant ocular dominance shift so that the response magnitude maps of both ipsi- (open) and contralateral (deprived) eye are now equally dark, the histograms of ocular dominance scores shift to the left (compare a to b and c to d) and colder colours prevail in the 2-D ocular dominance maps. In the two older animal groups, PD130 and PD215 mice, monocular deprivation for 7 days (f) or 14 days (h) fail to induce ocular dominance shifts and both histograms of ocular dominance scores and 2-D ocular dominance maps are similar to control animals (compare e to f and g to h). The scale bar is 1 mm and applies to all panels showing maps. Abbreviations: MD = monocular deprivation, OD = ocular dominance, contra = contralateral eye, ipsi = ipsilateral eye.

ODIs of control and monocularly deprived animals of all age groups. A positive ODI indicates dominance of the contralateral eye, a negative ODI ipsilateral dominance. Symbols represent ODI values of individual animals; means are marked by the thick horizontal lines. Circles represent values obtained from control animals, triangles, squares and diamonds values of animals after 4 days (4d), 7 days (7d) and 14 days (14d) monocular deprivation, respectively. Note that four days of monocular deprivation in PD25 and 7 days of monocular deprivation in PD95 animals induced a significant ocular dominance shift towards the open eye (p<0.001 and p<0.01, respectively, Bonferroni-corrected t-test). In both PD130 and PD215 animals, monocular deprivation has no such effect. In addition, the ODI of PD95 animals after 7 days of monocular deprivation was significantly different from the ODIs of PD130 and PD215 animals after the same deprivation period (p<0.05 and p<0.01, respectively, Bonferroni-corrected t-test).

Visual acuity of the animals was analyzed using a virtual optomotor system (Prusky et al., 2004). During 7 days of monocular deprivation and daily testing, spatial frequency selectivity of the optokinetic response of the nondeprived (open) eye increased from 0.39 cyc/deg to approximately 0.52 cyc/deg. While interocular plasticity was present in all analyzed age groups, it was significantly stronger in PD95 compared to PD130 and PD215 animals (p<0.01 and p<0.001), and in PD25 animals compared to PD215 animals (p<0.01, Bonferroni post hoc).