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:…projection neurons [medium spiny neurons (MSNs)] increase their firing rate
following local application of GABA antagonists (Bernardi et al., 1976; Nisenbaum and Berger, 1992; Kita, 1996; Darbin and Wichmann, 2008), which should, in theory, increase inhibition to the GPe via the indirect pathway.
Category: