Fig. 2

Learning and memory were significantly improved after insulin administration. a Episodic memory was affected in DMO and an overall improvement was observed after insulin administration in paradigms under study: “what” (**p < 0.01 vs. rest of the groups, ‡‡p < 0.01 vs Control, Control + IN-Ins, STZ + ICV-Ins, STZ + IN-Ins, ††p < 0.01 vs. Control + IN-Ins and STZ + IN-Ins), “where” (**p = 0.001 vs. rest of the groups), “when” (††p = 0.001 vs. Control + IN-Ins and STZ + IN-Ins) (Control n = 26, Control + ICV-Ins n = 19, Control + IN-Ins n = 8, STZ n = 15, STZ + ICV-Ins n = 12 and STZ + IN-Ins n = 6). b DMO were significantly impaied in the acquisition phase of the MWM and insulin treatment reversed this situation (day 1: ♯p = 0.012 vs. Control + IN-Ins, day 2: **p < 0.01 vs. rest of the groups, ††p < 0.01 vs. Control + IN-Ins and STZ + IN-Ins, day 3 ‡‡p < 0.01 vs. Control + IN-Ins, STZ-IN-Ins, Control and Control-ICV-Ins groups, ††p < 0.01 vs. Control + IN-Ins and STZ + IN-Ins, day 4: **p < 0.01 vs. rest of the groups, ††p < 0.01 vs. Control − +IN-Ins and STZ + IN-Ins). Two-way ANOVA was used to detect a groupXday interaction and one-way ANOVA, followed by Tuckey b or Tamhane test was used for further assessment of individual days. c Retention phase of the MWM also revealed an overall improvement after insulin administration to DMO (**p < 0.01 vs. rest of the groups) (Control n = 28, Control + ICV-Ins n = 17, Control + IN-Ins n = 8, STZ n = 17, STZ + ICV-Ins n = 10 and STZ + IN-Ins n = 6). Differences were detected by one-way ANOVA, followed by Tuckey b test