An agent uses at least one selected from the group consisting of an imidazole dipeptide and a metabolite thereof as an active ingredient. The present invention also provides an agent for improving a neuropsychologic function, which contains at least one selected from the group consisting of an imidazole dipeptide and a metabolite thereof as an active ingredient. The present invention also provides an agent for changing expression of a transporter such as SLC23A2, which contains at least one selected from the group consisting of an imidazole dipeptide and a metabolite thereof, and an agent for controlling blood concentration of a cytokine such as IP-10, which contains at least one selected from the group consisting of an imidazole dipeptide and a metabolite thereof, as well as an expression analysis method for detecting improvement or degradation of a neuropsychologic function, and a kit for detecting improvement or degradation of a neuropsychologic function.
