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:…leukoariosis), metabolic disorder (diabetes), psychiatric disorder (Axis I disorders except phobias), Mini Mental Status Exam score< 28, and over two years of piano playing within the past five years due to potentially atypical signal dynamics in primary sensorimotor cortex (Krampe et al. 2002).
Category: