Stroke Detection: Fmri's Power And Limits

Functional magnetic resonance imaging (fMRI) is a non-invasive imaging technique that can be used to study the brain activity of stroke patients. fMRI can be used to study the pathophysiology of stroke and the impact of stroke on brain networks. It can also be used to study the brain's recovery and reorganization following a stroke.

fMRI studies of stroke patients have shown that brain networks have temporal features that are disregarded in standard fMRI analysis, which focuses on spatial features. These temporal features include the duration of network activations, which have been found to vary in stroke patients compared to healthy individuals.

fMRI has also been used to study the impact of stroke on functional connectivity between brain regions. Interhemispheric connectivity has been found to greatly reduce in the acute stage following a stroke, even in regions outside the lesioned area.

In preclinical studies, fMRI has been used to study the recovery of brain function and connectivity following experimental stroke in animal models. However, preclinical fMRI studies are limited by the need to anaesthetize animals, which can affect the BOLD response.

fMRI can be used to study stroke pathophysiology

Functional magnetic resonance imaging (fMRI) can be used to study stroke pathophysiology. In particular, analyses of fMRI signals at rest were directed at quantifying the impact of stroke on spatial features of brain networks. However, brain networks have intrinsic time features that were, so far, disregarded in these analyses. In consequence, standard fMRI analysis failed to capture temporal imbalance resulting from stroke lesions, hence restricting their ability to reveal the interdependent pathological changes in structural and temporal network features following stroke.

Here, we longitudinally analyzed hemodynamic-informed transient activity in a large cohort of stroke patients to assess spatial and temporal changes of brain networks after stroke. Metrics extracted from the hemodynamic-informed transient activity were replicable within- and between-individuals in healthy participants, hence supporting their robustness and their clinical applicability. While large-scale spatial patterns of brain networks were preserved after stroke, their durations were altered, with stroke subjects exhibiting a varied pattern of longer and shorter network activations compared to healthy individuals.

Specifically, patients showed a longer duration in the lateral precentral gyrus and anterior cingulum, and a shorter duration in the occipital lobe and in the cerebellum. These temporal alterations were associated with white matter damage in projection and association pathways. Furthermore, they were tied to deficits in specific behavioral domains as restoration of healthy brain dynamics paralleled recovery of cognitive functions (attention, language and spatial memory), but was not significantly correlated to motor recovery.

These findings underscore the critical importance of network temporal properties in dissecting the pathophysiology of brain changes after stroke, thus shedding new light on the clinical potential of time-resolved methods for fMRI analysis.

fMRI can be used to study the impact of stroke on spatial features of brain networks

Functional magnetic resonance imaging (fMRI) has been widely used to study stroke pathophysiology. Analyses of fMRI signals at rest have been directed at quantifying the impact of stroke on spatial features of brain networks. However, brain networks have intrinsic time features that have been disregarded in these analyses. Standard fMRI analysis has failed to capture temporal imbalance resulting from stroke lesions, restricting its ability to reveal the interdependent pathological changes in structural and temporal network features following stroke.

In a study, hemodynamic-informed transient activity was longitudinally analysed in a large cohort of stroke patients to assess spatial and temporal changes of brain networks after stroke. Metrics extracted from the hemodynamic-informed transient activity were replicable within- and between-individuals in healthy participants, supporting their robustness and clinical applicability. While large-scale spatial patterns of brain networks were preserved after stroke, their durations were altered, with stroke subjects exhibiting a varied pattern of longer and shorter network activations compared to healthy individuals. Specifically, patients showed a longer duration in the lateral precentral gyrus and anterior cingulum, and a shorter duration in the occipital lobe and in the cerebellum. These temporal alterations were associated with white matter damage in projection and association pathways. Furthermore, they were tied to deficits in specific behavioural domains as restoration of healthy brain dynamics paralleled recovery of cognitive functions (attention, language and spatial memory), but was not significantly correlated to motor recovery.

In another study, Fugl-Meyer Assessments (FMA) revealed significant motor improvement in the chronic stroke group receiving active stimulation. Motor changes in this group were correlated in a data-driven fashion with imaging features, including functional connectivity (FC), surface-based morphometry, electric field modelling and network topology, focusing on relevant regions of interest. The feature most strongly associated with FMA improvement in the chronic stroke cohort was graph topology of the dorsal attention network (DAN), one of the regions surveyed and one with direct connections to each of the areas with FC changes. Chronic stroke subjects with a greater degree of motor improvement had lower signal transmission cost through the DAN.

fMRI can be used to study the impact of stroke on temporal features of brain networks

Functional magnetic resonance imaging (fMRI) can be used to study the impact of stroke on temporal features of brain networks. fMRI has been widely employed to study stroke pathophysiology. Analyses of fMRI signals at rest were directed at quantifying the impact of stroke on spatial features of brain networks. However, brain networks have intrinsic time features that were, so far, disregarded in these analyses. In consequence, standard fMRI analysis failed to capture temporal imbalance resulting from stroke lesions, hence restricting their ability to reveal the interdependent pathological changes in structural and temporal network features following stroke.

Here, we longitudinally analyzed hemodynamic-informed transient activity in a large cohort of stroke patients (n = 103) to assess spatial and temporal changes of brain networks after stroke. Metrics extracted from the hemodynamic-informed transient activity were replicable within- and between-individuals in healthy participants, hence supporting their robustness and their clinical applicability. While large-scale spatial patterns of brain networks were preserved after stroke, their durations were altered, with stroke subjects exhibiting a varied pattern of longer and shorter network activations compared to healthy individuals. Specifically, patients showed a longer duration in the lateral precentral gyrus and anterior cingulum, and a shorter duration in the occipital lobe and in the cerebellum. These temporal alterations were associated with white matter damage in projection and association pathways. Furthermore, they were tied to deficits in specific behavioral domains as restoration of healthy brain dynamics paralleled recovery of cognitive functions (attention, language and spatial memory), but was not significantly correlated to motor recovery. These findings underscore the critical importance of network temporal properties in dissecting the pathophysiology of brain changes after stroke, thus shedding new light on the clinical potential of time-resolved methods for fMRI analysis.

fMRI can be used to study the impact of stroke on brain networks in the acute stage

Functional magnetic resonance imaging (fMRI) can be used to study the impact of stroke on brain networks in the acute stage. fMRI can be used to observe the influence of stroke on brain networks and reveal the neuroplasticity mechanism of post-stroke rehabilitation.

FMRI can be used to study the impact of stroke on brain networks by measuring changes in blood oxygen levels in the brain. This technique can be used to assess functional connectivity, which is a method of identifying correlation patterns between different brain regions. By using fMRI, researchers can determine the functional reorganisation of the cerebral cortex, changes in inter-hemispheric balance, and activity changes in the hemispheres.

In particular, resting-state fMRI has been used to study stroke pathophysiology and quantify the impact of stroke on spatial features of brain networks. Resting-state fMRI can be used to investigate the impact of stroke on the functional connectivity of the motor network in acute ischemic stroke patients. It can also be used to evaluate the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity and connectivity in stroke patients with movement disorders.

FMRI has several advantages over other imaging techniques. It has better temporal resolution than PET and SPECT, and superior spatial resolution compared to EEG and MEG. It is also non-invasive and can be easily integrated into routine clinical MRI.

fMRI can be used to study the impact of stroke on brain networks in the chronic stage

Functional magnetic resonance imaging (fMRI) can be used to study the impact of stroke on brain networks in the chronic stage. fMRI has been widely used to study stroke pathophysiology, including the impact of stroke on the spatial features of brain networks. However, standard fMRI analysis has failed to capture temporal imbalance resulting from stroke lesions, restricting its ability to reveal interdependent pathological changes in structural and temporal network features following a stroke.

A recent study used fMRI to analyse hemodynamic-informed transient activity in a large cohort of stroke patients to assess spatial and temporal changes of brain networks after a stroke. The study found that while large-scale spatial patterns of brain networks were preserved after a stroke, their durations were altered, with stroke subjects exhibiting a varied pattern of longer and shorter network activations compared to healthy individuals. These temporal alterations were associated with white matter damage in projection and association pathways and were tied to deficits in specific behavioural domains. The findings suggest that fMRI can be used to study the impact of stroke on brain networks in the chronic stage and that the network temporal properties are critical in dissecting the pathophysiology of brain changes after a stroke.

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