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Brain maturation from childhood to adulthood is associated with changes in structural and functional connectivity between remote brain regions. Altered connectivity plays an important role in the pathology of autism spectrum disorder (ASD), a severe neurodevelopmental disorder. ASD is associated with abnormal brain development and structurally altered interhemispheric connections. Cortico-cortical connectivity can be studied by a combination of transcranial magnetic stimulation (TMS) with concurrent EEG (TMS-EEG). TMS-evoked Interhemispheric Signal Propagation (ISP) is a correlate of interhemispheric connectivity related to the microstructure of the corpus callosum (CC). We used TMS-EEG to measure ISP in 22 ASD subjects (10-21 years) and 22 typically developing control subjects (9-19 years). We expected (1) maturational changes of ISP from childhood to young adulthood and also (2) reduced interhemispheric signal transfer in ASD. ISP was positively correlated with age in both ASD and typically developing control subjects. No difference in ISP between ASD and typically developing controls was found. Our findings demonstrate maturation of effective interhemispheric connectivity during adolescence. As ISP is related to the microstructure of the CC, the developmental change of ISP likely reflects maturation of the CC during the second life decade. The results support ISP as a valid parameter reflecting functional interhemispheric connectivity. Our results do not support a global deficit of interhemispheric connectivity in ASD.

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Despite a growing understanding of human brain function, it is still unclear how conscious experience emerges from neural activity. A much-debated question in the search for the neural underpinnings of consciousness is whether prefrontal cortex actively shapes conscious experience or, alternatively, serves only complementary cognitive functions such as evaluating and acting on the contents of consciousness.Here, we studied the neural mechanisms of bistable perception to elucidate the role of prefrontal cortex in consciousness. Human participants reported periodic changes in conscious experience that were induced by conflicting sensory information. Two functional magnetic resonance imaging experiments showed that prefrontal brain activity in inferior frontal cortex signals the conflict between conscious experience and available sensory information. In a third experiment, inhibitory transcranial magnetic stimulation revealed that a disruption of neural activity in inferior frontal cortex leads to a decrease of conflict-driven changes in conscious experience.Our results indicate that, by engaging in iterative and reciprocal interactions with sensory brain regions, inferior frontal cortex plays a critical role in both the detection and the resolution of perceptual conflicts. This points to a causal influence of prefrontal brain activity on the dynamic unfolding of conscious experience. One-sentence Summary Inferior frontal cortex detects and resolves perceptual conflict during bistable perception.