The pathophysiology of hallucinations remains mysterious. This research aims to specifically explore the interaction between hallucinations and spontaneous resting-state activity. We used multimodal magnetic resonance imaging during hallucinations occurrence in 20 drug-free adolescents with a "brief psychotic disorder." They were furthermore compared with 20 matched controls at rest or during exteroceptive stimuli. Anatomical and functional symptom-mapping demonstrated reduced cortical thickness and increased blood oxygen level-dependent signal in modality-dependent association sensory cortices during auditory, visual, and multisensory hallucinations. On the contrary, primary-sensory-cortex recruitment was not systematic and was shown to be associated with increased vividness of the hallucinatory experiences. Spatiotemporal activity patterns in the default-mode network (DMN) during hallucinations and symptom-free periods in patients were compared with patterns measured in healthy individuals. A disengagement of the DMN was concomitant to hallucinations, as for exogenous stimulations in healthy participants. Specifically, spatial and temporal instabilities of the DMN correlated with the severity of hallucinations but persisted during symptom-free periods. These results suggest that hallucinatory experiences emerge from a spontaneous DMN withdrawal, providing a convincing model for hallucinations beyond the auditory modality.

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Evidence for cortical sensory activation in the human fetus at the beginning of the third trimester of pregnancy was provided in a recent imaging study. Although hearing is functional before birth, it is not clear whether recognition of the mother's voice is learned in utero or rapidly following delivery. We developed an original fMRI procedure that allows for the specific exploration of fetal brain response to auditory stimuli. This procedure provides the first in vivo evidence for the development of maternal voice recognition in utero between 33 and 34 weeks of gestation. This methodology could have crucial implications in the study of fetal cognition.