Ketamine changes the local resting-state functional properties of anesthetized-monkey brain

Objective: Ketamine is a well-known anesthetic. 'Recreational' use of ketamine common induces psychosis-like symptoms and cognitive impairments. The acute and chronic effects of ketamine on relevant brain circuits have been studied, but the effects of single-dose ketamine administration on the local resting-state functional properties of the brain remain unknown. In this study, we aimed to assess the effects of single-dose ketamine administration on the brain local intrinsic properties. Methods: We used resting-state functional magnetic resonance imaging (rs-fMRI) to explore the ketamine-induced alterations of brain intrinsic properties. Seven adult rhesus monkeys were imaged with rs-fMRI to examine the fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity (ReHo) in the brain before and after ketamine injection. Paired comparisons were used to detect the significantly altered regions. Results: Results showed that the fALFF of the prefrontal cortex (p = 0.046), caudate nucleus (left side, p = 0.018; right side, p = 0.025), and putamen (p = 0.020) in post-injection stage significantly increased compared with those in pre-injection period. The ReHo of nucleus accumbens (p = 0.049), caudate nucleus (p = 0.037), and hippocampus (p = 0.025) increased after ketamine injection, but that of prefrontal cortex decreased (p < 0.05). Conclusions: These findings demonstrated that single-dose ketamine administration can change the regional intensity and synchronism of brain activity, thereby providing evidence of ketamine-induced abnormal resting state functional properties in primates. This evidence may help further elucidate the effects of ketamine on the cerebral resting status. (C) 2017 Published by Elsevier Inc.