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:Imaging studies showed reduced activation of visual cortices during vestibular stimulation (Brandt et al., 1998; Brandt, 1999; Bense et al., 2001), and this was hypothesized to be a cortical mechanism contributing to stabilize visual images during self-motion, along with brainstem reflexes (such as the vestibulo-ocular reflex).
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