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:Animal work shows that the BLA is required for food-predictive external cues to promote eating in the absence of homeostatic need because crossed unilateral lesions of the BLA and lateral hypothalamus disrupt cue-potentiated feeding (Petrovich et al., 2002, 2005).
Category: