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:…into 34 different gyral regions per hemisphere, for each of which a mean cortical thickness value was calculated (Desikan et al. 2006; Fischl et al. 2004b) Automated Freesurfer subcortical parcellation was employed to extract volumes for the amygdala, hippocampus, whole brain grey…
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