Figure 5.

Object recognition test of short-term memory. Recognition index of novel object exploration is exploration time on new object/total exploration time (RI = t _n/(t _n + t _f)). The recognition index (RI) of a novel object in fentanyl group was not significantly different from that for the unoperated sham controls. However, a significant difference (*P = 0.045) was evidenced between the fentanyl group compared to the saline group, showing better cognitive function for the first group. A difference was also seen between the controls: unoperated sham rats displayed significantly (^§ P = 0.025) better short-term memory compared to saline-treated rats. Values are mean ± SD.