Psychedelic drugs such as LSD, which activate the serotonin 2A receptor, produce profound changes in consciousness and are linked to increased entropy in spontaneous brain activity. This study provides the first model-based explanation for that entropy increase by extending a whole-brain model of serotonin neuromodulation. The model reproduced the overall rise in neural entropy seen in prior experiments. Entropy increased across all brain regions, with the largest effects in visuo-occipital areas. At the whole-brain level, this reconfiguration was not well explained by the density of serotonin 2A receptors but was closely related to the topological properties of the brain's anatomical connectivity.
Within social cognition, some researchers argue that understanding others relies on dynamic, second-person interactions rather than detached observation. This enactivist view splits over whether such intersubjective processes are innate. Nativist enactivists cite neonatal imitation as evidence that infants possess an embodied form of understanding others from birth, while empiricist enactivists claim these processes are learned through social interaction. A critical examination of studies on neonate imitation finds that only tongue protrusion imitation is consistently replicated across studies; evidence for other gestures is mixed. If neonates imitate only one gesture, a simpler explanation for tongue protrusion is possible. Thus, the nativist claim that second-person interactive processes are present at birth appears unsupported. The evidence aligns with the empiricist position, suggesting that such interactive understanding develops over time.