No abstract

Summary Perceptual history can exert pronounced effects on the contents of conscious experience: when confronted with completely ambiguous stimuli, perception does not waver at random between diverging stimulus interpretations but sticks with recent percepts for prolonged intervals. Here, we investigated the relevance of perceptual history in situations more similar to everyday experience, where sensory stimuli are usually not completely ambiguous. Using partially ambiguous visual stimuli, we found that the balance between past and present is not stable over time but slowly fluctuates between two opposing modes. For time periods of up to several minutes, perception was either largely determined by perceptual history or driven predominantly by disambiguating sensory evidence. Computational modeling suggested that the construction of unambiguous conscious experiences is modulated by slow fluctuations between internally and externally oriented modes of sensory processing.

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.

Objectives We aimed to evaluate optic chiasm (OC) measures as potential imaging marker for anterior optic pathway damage assessment in the context of neuromyelitis optica spectrum disorders (NMOSD). Materials and method This cross-sectional study included 39 patients exclusively with aquaporin 4-IgG seropositive NMOSD of which 25 patients had a history of optic neuritis (NMOSD-ON) and 37 age-and sex-matched healthy controls (HC). OC heights, width, and area were measured using standard 3D T1-weighted MRI. Sensitivity of these measures to detect neurodegeneration in the anterior optic pathway was assessed in receiver operating characteristics analyses. Correlation coefficients were used to assess associations with structural measures of the anterior optic pathway (optic nerve dimensions, retinal ganglion cell loss) and clinical measures (visual function and disease duration). Results OC heights and area were significantly smaller in NMOSD-ON compared to HC (NMOSD-ON vs. HC p < 0.0001). An OC area smaller than 22.5 mm 2 yielded a sensitivity of 0.92 and a specificity of 0.92 in separating chiasms of NMOSD-ON from HC. OC area correlated well with structural and clinical measures in NMOSD-ON: optic nerve diameter (r = 0.4, p = 0.047), peripapillary retinal nerve fiber layer thickness (r = 0.59, p = 0.003), global visual acuity (r = − 0.57, p = 0.013), and diseases duration (r = − 0.5, p = 0.012). Conclusion Our results suggest that OC measures are promising and easily accessible imaging markers for the assessment of anterior optic pathway damage.