Critical period-specific increase of the level of coincidence of binocular synaptic inputs. A, Solid curves are averaged subthreshold PSP responses of a binocular cell during the pre-CP, evoked by full-field static gratings (at 3 different spatial phases, left) presented alternately to contralateral (blue) and ipsilateral (red) eye, in a mouse under ketamine/medetomidine anesthesia. Shading indicates trial-to-trial SD of membrane potential. Dashed lines represent times of stimuli ON and OFF, and solid blue and red lines indicate the onset times of contralateral and ipsilateral PSPs, respectively. Bottom, Distribution of onset latencies calculated by bootstrapping 500 times. B, C, Same as A, except for binocular cells recorded during the CP (B) and adulthood (C). D, Summary of the mean latency of evoked PSPs from experiments shown in A–C. Data connected with a line are from the same cell. Filled circles with error bars: mean ± SD. Triangles, Data from animals under pentobarbital anesthesia. p values are calculated by the Wilcoxon signed-rank test. E, Cumulative distribution of the ipsi–contra latency difference in pre-CP, CP, and adulthood. Significant difference was found between CP and pre-CP (p < 10−16, Kolmogorov–Smirnov test), CP and adulthood (p < 10−17).
