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:6(d)) may seem to contrast the decreased firing rates reported in previous modeling studies (Bojak and Liley, 2005; Hutt and Longtin, 2010; Steyn-Ross et al., 1999) and observed in experiments (Antkowiak, 1999).
Category: