2.5 Statistical analysis
R version 3.5.3 was used for statistical analysis. P < 0.05 indicated statistical signif-icance. Measurement data are expressed as mean ± standard deviation (x ± s) and counti-ng data as rate (%). The correct recognition rate of odors in each test was calculated, and the test scores in the modification process were tested by paired sample Friedman M test. The correct recognition rate of odors in the SSOI and CMOI tests was tested by the paire-d sample Wilcoxon signed rank-sum test. Draw FIGURE 1 and FIGURE 2 with GraphP-ad Prism 8 (GraphPad Software, La Jolla, CA, USA).