Spacetime in the Brain: rapid brain network reorganization in visual processing and recovery

Purpose: Although it is known that optic nerve damage, for example after glaucoma or optic neuropathy, a local event, alters global functional connectivity networks (FCN) in the brain resting state, it is unknown if and how visual deprivation a ects the dynamics of transient and rapid brain FCN changes. The synchronization between brain regions is essential for the integration between visual and non-visual modalities in time and space, and if a patient detects - or fails to detect - visual stimuli is rather variable and may depend on the FCN response to visual stimuli.

Methods: In patients with optic nerve damage (n=19) and healthy subjects (n=14), the ability to detect super-threshold stimuli was related to parameters of the ”event related network analysis (ERNA) based on graph theory immediately following successful (hits) or unsuccessful stimulus detections (misses). Graph-based features of transient and dynamically synchronized networks where described following stimulus onset to compare di erent visual field states of normal and partially damaged visual field sectors (areas of residual vision, ARVs).

Results: Compared to controls, hits in the intact visual field sector in patients where associated with connectivity topology changes characterized by less cluster, but more large scale connections with low e ciency. In areas of residual vision, hits in patients evoked a network dynamic change with weaker node strength and less clustering, shorter characteristic path length and poorer small-world-ness than hits in their intact field. These rapid FCN topology changes happened primarily in high alpha and beta band in the late ”cognitive processing stage (300-600 ms).

Conclusion: Patients with optic nerve damage have a weaker processing balance of functional integration and segregation during the cognition which reduces local and global information interactions. FCN fluctuations are thus a physiological correlate of response variability of visual functions and network modulation might be a possible target for modulating visual performance.