Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:…it is also in the same quantitative range as the induction of BDNF, a neurotrophic mediator of exercise in the brain, as well as cFOS, ARC, and ZIF268, important indicators for the activity state of neurons (Hunt et al., 1987; Lyford et al., 1995; Rusak et al., 1990; Saffen et al., 1988).
Category: