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:Secondary to this, a decrease of mGluR protein persists into adulthood and causes altered synaptic learning rules and attention behavior (Counotte et al., 2011a; Goriounova and Mansvelder, 2012b).
Category: