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:KEY WORDS: reuniens nucleus; rhomboid nucleus; radial maze DNM; DNMTP
INTRODUCTION
Medial thalamic lesions produce core signs of memory impairment comparable to medial temporal lobe amnesia (McKee and Squire, 1992; Van der Werf et al., 2003; Gold and Squire, 2006).
Category: