Achard and Bullmore (2007) investigated the efficiency and cost of human brain functional networks using functional magnetic resonance imaging (fMRI) data from young and old healthy volunteers. They found that brain functional networks have small-world properties, characterized by high global and local efficiency of parallel information processing with low connection cost. Efficiency was reduced disproportionately in older individuals, particularly in frontal and temporal regions. Dopamine antagonism also impaired network efficiency, but the effects were localized and did not interact with age. The study highlights that brain functional networks have economical small-world properties, which are differently affected by normal aging and pharmacological blockade of dopamine transmission. The results suggest that these networks support efficient parallel information transfer at relatively low cost, and their performance is detrimentally affected by aging and dopamine receptor antagonism. The study also emphasizes the importance of considering the topological properties of brain networks in understanding developmental, pathological, and pharmacological effects on brain function. The findings have implications for computational biology and could inform future research on brain network dynamics.Achard and Bullmore (2007) investigated the efficiency and cost of human brain functional networks using functional magnetic resonance imaging (fMRI) data from young and old healthy volunteers. They found that brain functional networks have small-world properties, characterized by high global and local efficiency of parallel information processing with low connection cost. Efficiency was reduced disproportionately in older individuals, particularly in frontal and temporal regions. Dopamine antagonism also impaired network efficiency, but the effects were localized and did not interact with age. The study highlights that brain functional networks have economical small-world properties, which are differently affected by normal aging and pharmacological blockade of dopamine transmission. The results suggest that these networks support efficient parallel information transfer at relatively low cost, and their performance is detrimentally affected by aging and dopamine receptor antagonism. The study also emphasizes the importance of considering the topological properties of brain networks in understanding developmental, pathological, and pharmacological effects on brain function. The findings have implications for computational biology and could inform future research on brain network dynamics.