Topological changes of fast large-scale brain dynamics in Mild Cognitive Impairment predict the decay of the hippocampal memory

Abstract

Functional connectivity has been widely used as a framework to investigate widespread brain interactions underlying cognitive deficits in Mild Cognitive Impairment (MCI). However, one of the main constraints of functional connectivity is that it is averaged over a time interval and therefore may not take into account the aperiodic and scale-free burst of activity (i.e., the neuronal avalanches) characterising the large-scale dynamic activity of the brain. Here, we used the recently proposed Avalanche Transition Matrix framework to source-reconstructed magnetoencephalography signals in a cohort of 32 MCI patients and 32 healthy controls (HC) to deepen the spatio-temporal features of neuronal avalanches and explore their topological properties. Our results showed that MCI patients exhibited a more centralised network (as assessed by higher values of degree divergence and leaf fraction) compared to HC. Furthermore, we found that the degree divergence (in the theta band) was predictive of the episodic memory impairment, assessed by FCSRT immediate total recall. These findings highlight the role of dynamical features in detecting functional and structural changes in clinical conditions. Hopefully, the proposed framework may be helpful in monitoring the development of the disease by adding subtle information that contributes to a more thorough phenotypical assessment of patients.

Criticality of neuronal avalanches in human sleep and their relationship with sleep macro- and micro-architecture

“… 17 Indeed, a number of theoretical and numerical results show that criticality is associated with optimal information processing and computation. 17 , 18 , 19 , 20 Moreover, reduced flexibility 21 , 22 , 23 , 24 and breakdown (or alteration) of long-range temporal correlations in brain dynamics 25 , 26 have been associated with neurological diseases and reduced information transfer.…”

Flexibility of brain dynamics is increased and predicts clinical impairment in Relapsing-Remitting but not in Secondary Progressive Multiple Sclerosis

“…In the present study, we investigated the flexibility of the brain dynamics in MS and its relationship with the clinical phenotypes. In particular, following our previous studies carried out on neurodegenerative diseases, including ALS 18 , AD 19 and PD 17 , where a reduction of the functional repertoire has been consistently found, we hypothesised that MS could express different behaviours as a function of the prevalence of neuroinflammation or neurodegeneration. When we looked at the different MS clinical phenotypes, we found that the significant differences in the flexibility of the brain dynamics were mainly attributable to the RRMS phenotype.…”

“…Based on our previous observations about brain dynamics in neurodegenerative diseases such as probable Alzheimer's disease (AD) 19 , Parkinson's disease (PD) 17 and Amyotrophic lateral sclerosis (ALS) 18 , in the present work we hypothesise that MS could also be characterised by variations in brain flexibility, which would be related to, and predictive of, the subject specific clinical impairment. We also wondered whether the underlying disease mechanisms that characterise the two distinct forms of MS (relapsing remitting and progressive) could reflect in different brain dynamics and if this difference could help in predicting clinical disability.…”