Dynamics of brain connectivity after stroke

Abstract

Recovery from a stroke is a dynamic time-dependent process, in which the central nervous system reorganises to accommodate for the impact of the injury. The purpose of this paper is to review recent longitudinal studies of changes in brain connectivity after stroke. A systematic review of research papers reporting functional or effective connectivity at two or more time points in stroke patients was conducted. Stroke leads to an early reduction of connectivity in the motor network. With recovery time, the connectivity increases and can reach the same levels as in healthy participants. The increase in connectivity is correlated with functional motor gains. A new, more randomised pattern of connectivity may then emerge in the longer term. In some instances, a pattern of increased connectivity even higher than in healthy controls can be observed, and is related either to a specific time point or to a specific neural structure. Rehabilitation interventions can help improve connectivity between specific regions. Moreover, motor network connectivity undergoes reorganisation during recovery from a stroke and can be related to behavioural recovery. A detailed analysis of changes in connectivity pattern may enable a better understanding of adaptation to a stroke and how compensatory mechanisms in the brain may be supported by rehabilitation.

Multimodal Neuroimaging Using Concurrent EEG/fNIRS for Poststroke Recovery Assessment: An Exploratory Study

“…Therefore, it is of great importance to explore useful biomarkers for insightful assessments of changes in brain motor function across a period of therapy and an effective management of a rehabilitation program. Numerous lines of evidence have demonstrated that stroke lesion at both cortical and subcortical area could induce brain plasticity on the cortical level, such as altered interhemispheric connectivity between bilateral motor cortex (particularly M1) and abnormal regional activation, 42 which opens new opportunities for us to explore the network aspects of brain function and brain plasticity associated with poststroke recovery. In this study we presented an fNIRS-informed EEG source imaging approach to investigate the brain network alterations caused by stroke during a hand-clenching task.…”

Graded fMRI Neurofeedback Training of Motor Imagery in Middle Cerebral Artery Stroke Patients: A Preregistered Proof-of-Concept Study

“…As an alternative to providing feedback based on an average signal from an entire ROI, future fMRI-NF studies may benefit from exploring connectome-based (Ramot et al, 2017 ; Noble et al, 2020 ) and multivariate, i.e., decoded, neurofeedback (Shibata et al, 2019 ). Connectome-based neurofeedback allows targeting entire networks of correlated activity between nodes of motor networks and support their reorganization (Desowska and Turner, 2019 ), allowing to probe causally functional network models of impairment/recovery (Mehler and Kording, 2018 ). Of particular interest for future work may be targeting dynamic connectivity states that vary with motor impairment (Bonkhoff et al, 2020 ).…”

Dynamic Neural Network Changes Revealed by Voxel-Based Functional Connectivity Strength in Left Basal Ganglia Ischemic Stroke

“…Additionally, future studies should collect more samples to further verify our results. Fourth, the study examined functional changes using only rs-fMRI, while recent studies have indicated that reorganization of brain function was also related to damage to brain structure ( Liu J. et al, 2015 ; Thiel and Vahdat, 2015 ; Desowska and Turner, 2019 ). Thus, to better understand the neural mechanisms of reorganization, further studies are required to combine FC with structural studies.…”

“…Thus, increased FCS in the MPFC and INS may imply that motor and cognitive manipulation had become stronger because of the shortage of motor output affected by the infarction lesion (Fan et al, 2015). It should be noted that those increased regions were primarily localized in the contralesional hemisphere, which was taken as the compensatory mechanism to compensate for the motor impairment caused by the damaged brain region (Zheng et al, 2016;Desowska and Turner, 2019).…”

“…Although abundant rs-fMRI studies of stroke have been reported on large-scale brain lesions and provided valuable content, lesion location is still an important factor in exploring brain function. More stroke studies with lesions in isolated brain regions are needed to address these issues (Park et al, 2016;Rondina et al, 2016;Desowska and Turner, 2019). As mentioned above, BG stroke could cause long-term motor impairment, but the mechanism of its brain function has rarely been studied and not been elucidated.…”