The vivid sense of depth and solidity that defines stereopsis is usually attributed to the brain's processing of binocular disparity. However, the same impression can occur when viewing a picture with one eye through a small hole. By measuring EEG brain activity while people looked at images of 2D and 3D shapes under different viewing conditions, a specific pattern of neural activity was identified that accompanied this qualitative depth experience. Only the monocular aperture condition, which produces the strongest depth impression, showed elevated gamma-band synchronization in the parietal cortex when comparing 3D to 2D shapes. This suggests that the subjective experience of stereopsis involves neural processes distinct from those that compute binocular disparity.
Using the critical Ising model of the brain, integrated information—a measure of consciousness—was measured in toy models of generic neural networks. Monte Carlo simulations were run on 159 random weighted networks analogous to small 5-node neural network motifs. Integrated information, as a type of order parameter like magnetism, undergoes a phase transition at the model's critical point, where the system's 'consciousness' is maximally susceptible to perturbations and on the boundary between ordered and disordered forms. This adds evidence that the emergence of consciousness coincides with self-organized criticality, evolution, the emergence of complexity, and the integration of complex systems.