To test this hypothesis, we used 9 and 18 months old mice, employed a battery of natural and learned behavioral tests to determine the delirium-like behavior [37], assessed the gut microbiota before and after the anesthesia/surgery by gene pyrosequencing of 16S rRNA, and measured levels of brain IL-6, synaptic marker and mitochondrial function as measures of neuroinflammation and cerebral dysfunction. This evidence concerns the gene IL6 and delirium.