Figure 4.

Spatial learning and memory ability in mice treated with polystyrene microplastics (PS-MPs). Mice were tested in a Morris water maze (MWM) experiment following treatment with PS-MPs for 180 days. (A) The experimental design of the MWM test is displayed. Day 1 was the visible platform phase, and the platform was set $1\mathrm{cm}$ above the water level. Days 2–5 comprised the hidden platform phase, and additional water was added to the pool to submerge the platform to $1\mathrm{cm}$ below the surface. Day 6 was the testing phase, and the platform was removed from the pool. The SMART digital tracking system (version 2.5; Panlab) was used to record the trial. The mean and SD summary data for quantification are shown in Table S3. $p$-Values for all comparisons are reported in Table S4. (B) The time it took the mice to move from the third quadrant to the target platform during the learning trials (days 1–5) was measured. The mean and SD summary data for quantification are shown in Table S3. $p$-Values for all comparisons are reported in Table S4. (C) Representative swimming routes of mice from the third quadrant to the target platform on the fifth and sixth days are shown. (D) The number of times the mice passed the target platform on sixth day are displayed. The mean and SD summary data for quantification are shown in Table S3. $p$-Values for all comparisons are reported in Table S4. (E) On the sixth day, the percentage of time the mice took in the quadrant where the target platform was placed was detected. Data are presented as the $\text{means}\pm \text{SD}$ ($N=10$ mice/per group). The mean and SD summary data for quantification are shown in Table S3. $p$-Values for all comparisons are reported in Table S4. *$p<0.05$; **$p<0.01$ vs. control, as determined by one-way ANOVA followed by Dunnett’s multiple comparison tests. Note: ANOVA, analysis of variance; SD, standard deviation.