Human Brain Mapping
October 21, 2019
Bhim M. Adhikari, Juergen Dukart, Joerg F. Hipp et al.
24 citations
Ketamine, given at subanesthetic doses to healthy volunteers, produces psychosis-like symptoms and reduces functional connectivity in the salience network, auditory network, and default mode network (DMN). Midazolam, a sedative, only reduces DMN connectivity. The pattern of connectivity deficits caused by ketamine positively correlates with the pattern seen in schizophrenia, whereas midazolam's effects do not. After subtracting midazolam's effects, the remaining ketamine-specific disconnectivity pattern still correlates with schizophrenia deficits. This suggests that ketamine's psychosis-like effects have a brain functional basis that overlaps with schizophrenia-related connectivity disruptions.
Journal of Psychopharmacology
January 21, 2019
Rebecca McMillan, Anna Forsyth, Doug Campbell et al.
23 citations
Ketamine infusion in healthy men increases blood-oxygen-level dependent signals across the cortex and decreases them in the subgenual anterior cingulate cortex, but the decrease is largely due to physiological noise, especially cardiac pulsatility, rather than neural activity. Modeling the pharmacological MRI response with a single time course misses the full range of neural dynamics; using simultaneously recorded electroencephalography power time series reveals distinct temporal responses to ketamine, though no EEG band correlated with the subgenual anterior cingulate cortex decrease.
Human Brain Mapping
December 6, 2019
Anna Forsyth, Rebecca McMillan, Doug Campbell et al.
19 citations
The validity of fMRI functional connectivity as a drug biomarker was tested by comparing seven preprocessing pipelines and by simultaneously measuring EEG and fMRI in a placebo-controlled, three-way crossover study with ketamine and midazolam. Independent components analysis (ICA)-denoising produced stronger reductions in connectivity after ketamine and weaker increases after midazolam than pipelines using physiological noise modelling or averaged signals from cerebrospinal fluid or white matter. This indicates that pipeline decisions should match a drug's unique noise structure; when unknown, extensive ICA denoising may sacrifice some signal but increase confidence in remaining results. No significant relationship was found between changes in electrophysiological and hemodynamic correlation structures, cautioning against cross-modal comparisons of pharmacologically-modulated functional connectivity.
bioRxiv Preprint Server
July 10, 2019
Joel Frohlich, Lynne M. Bird, John Dell’italia et al.
preprint
Children with Angelman syndrome, who are fully conscious, have brainwave patterns that look like those seen during unconsciousness, challenging theories that link consciousness to complex neural activity. However, when comparing wakefulness to sleep, the brainwaves of 35 children with Angelman syndrome show greater complexity during wakefulness, even when accounting for slow-wave activity. This supports the idea that consciousness is tied to neural complexity and warns against assuming a lack of consciousness based solely on EEG readings.