Article 1 Complexity 1 Dimensional complexity 1 Entropy 1 Functional magnetic resonance imaging (fMRI) 1 Healthy aging 1 Principal subspace analysis (PSA) 1 Resting-state fMRI 1 Rockland sample adult 1 brain function 1 brain region 1 entropy 1 frontal cortex 1 healthy aging 1 human 1 human experiment 1 mathematical analysis 1 medical research 1 nerve cell network 1 normal human 1 resting state network 1 sensorimotor cortex 1 variance 1