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:2007), indicating lower dopamine release in the NAcc and a lower behavioral response to psychostimulants in the DBA rather than the C57mice (Zocchi et al. 1998; Ventura et al. 2004a; b; Orsini et al. 2005).
Category: