Sampling and statistics

Summarized data were presented in figures as mean ± SEM with n values representing, in all cases, the number of biological replicates (number of cells, pairs or mice in each data set, as indicated in figure legends). Sample size for all experiments was estimated according to the standards in the field (Díaz-Alonso et al., 2017; Granger et al., 2013; Incontro et al., 2014; Orr et al., 2018). Genotype blinding (masking) was used for behavior experiments. Electrophysiology experiments were performed without masking.

Data analysis was carried out in Igor Pro (Wavemetrics) Excel (Microsoft), and GraphPad Prism (GraphPad Software). Unpaired t-test or Mann-Whitney U test were used to assess statistical significance in experiments involving unpaired data. Two-tailed Wilcoxon signed-rank test for experiments using paired data. For Morris water maze experiments, mixed effects analyses were employed to assess the effect of genotype and training in hidden platform and cued platform location performance and swim speed, while number of platform crossings and % time in quadrant in the 24 hr probe were analyzed using paired t-test and Wilcoxon signed-rank test. For measures directly comparing probe performance between genotypes (latency to first platform crossing and swim speed), Welch’s t-test and Mann-Whitney U test were used. LTP data in molecular replacement experiments was obtained from pairs of control and experimental neurons; however, some cells were lost during the experiment, as indicated in the LTP plot legends and figure legends. Consequently, the resulting datasets are a mix of interleaved and paired data, thus, comparisons were made using unpaired statistics. Statistical significance of LTP in HA-ΔCTD GluA1 vs WT mice experiments was also analyzed with unpaired statistics. All statistical significances were set as *p<0.05, **p<0.01, and ***p<0.001.