Dataset Information

Recovery of slow-5 oscillations in a longitudinal study of ischemic stroke patients.

ABSTRACT: Functional networks in resting-state fMRI are identified by characteristics of their intrinsic low-frequency oscillations, more specifically in terms of their synchronicity. With advanced aging and in clinical populations, this synchronicity among functionally linked regions is known to decrease and become disrupted, which may be associated with observed cognitive and behavioral changes. Previous work from our group has revealed that oscillations within the slow-5 frequency range (0.01-0.027 Hz) are particularly susceptible to disruptions in aging and following a stroke. In this study, we characterized longitudinally the changes in the slow-5 oscillations in stroke patients across two different time-points. We followed a group of ischemic stroke patients (n = 20) and another group of healthy older adults (n = 14) over two visits separated by a minimum of three months (average of 9 months). For the stroke patients, one visit occurred in their subacute window (10 days to 6 months after stroke onset), the other took place in their chronic window (> 6 months after stroke). Using a mid-order group ICA method on 10-minutes eyes-closed resting-state fMRI data, we assessed the frequency distributions of a component's representative time-courses for differences in regards to slow-5 spectral power. First, our stroke patients, in their subacute stage, exhibited lower amplitude slow-5 oscillations in comparison to their healthy counterparts. Second, over time in their chronic stage, those same patients showed a recovery of those oscillations, reaching near equivalence to the healthy older adult group. Our results indicate the possibility of an eventual recovery of those initially disrupted network oscillations to a near-normal level, providing potentially a biomarker for stroke recovery of the cortical system. This finding opens new avenues in infra-slow oscillation research and could serve as a useful biomarker in future treatments aimed at recovery.

SUBMITTER: La C

PROVIDER: S-EPMC4816902 | biostudies-other | 2016

REPOSITORIES: biostudies-other

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Recovery of slow-5 oscillations in a longitudinal study of ischemic stroke patients.

La C C Nair V A VA Mossahebi P P Stamm J J Birn R R Meyerand M E ME Prabhakaran V V

NeuroImage. Clinical 20160317

Functional networks in resting-state fMRI are identified by characteristics of their intrinsic low-frequency oscillations, more specifically in terms of their synchronicity. With advanced aging and in clinical populations, this synchronicity among functionally linked regions is known to decrease and become disrupted, which may be associated with observed cognitive and behavioral changes. Previous work from our group has revealed that oscillations within the slow-5 frequency range (0.01-0.027 Hz) ...[more]

PMID: 27077023

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Project description:The 'default-mode' network (DMN) has been investigated in the presence of various disorders, such as Alzheimer's disease and Autism spectrum disorders. More recently, this investigation has expanded to include patients with ischemic injury. Here, we characterized the effects of ischemic injury in terms of its spectral distribution of resting-state low-frequency oscillations and further investigated whether those specific disruptions were unique to the DMN, or rather more general, affecting the global cortical system. With 43 young healthy adults, 42 older healthy adults, 14 stroke patients in their early stage (<7 days after stroke onset), and 16 stroke patients in their later stage (between 1 to 6 months after stroke onset), this study showed that patterns of cortical system disruption may differ between healthy aging and following the event of an ischemic stroke. The stroke group in the later stage demonstrated a global reduction in the amplitude of the slow-5 oscillations (0.01-0.027 Hz) in the DMN as well as in the primary visual and sensorimotor networks, two 'task-positive' networks. In comparison to the young healthy group, the older healthy subjects presented a decrease in the amplitude of the slow-5 oscillations specific to the components of the DMN, while exhibiting an increase in oscillation power in the task-positive networks. These two processes of a decrease DMN and an increase in 'task-positive' slow-5 oscillations may potentially be related, with a deficit in DMN inhibition, leading to an elevation of oscillations in non-DMN systems. These findings also suggest that disruptions of the slow-5 oscillations in healthy aging may be more specific to the DMN while the disruptions of those oscillations following a stroke through remote (diaschisis) effects may be more widespread, highlighting a non-specificity of disruption on the DMN in stroke population. The mechanisms underlying those differing modes of network disruption need to be further explored to better inform our understanding of brain function in healthy individuals and following injury.

Project description:IntroductionStroke is one of the leading causes of substantial disability worldwide. Previous studies have shown brain functional and structural alterations in adults with stroke. However, few studies have examined the longitudinal reorganization in whole-brain structural networks in stroke.MethodsHere, we applied graph theoretical analysis to investigate the longitudinal topological organization of white matter networks in 20 ischemic stroke patients with a one-month interval between two timepoints. Two sets of clinical scores, Fugl-Meyer motor assessment (FMA) and neurological deficit scores (NDS), were assessed for all patients on the day the image data were collected.ResultsThe stroke patients exhibited significant increases in FMA scores and significant reductions in DNS between the two timepoints. All groups exhibited small-world organization (σ > 1) in the brain structural network, including a high clustering coefficient (γ > 1) and a low normalized characteristic path length (λ ≈ 1). However, compared to healthy controls, stroke patients showed significant decrease in nodal characteristics at the first timepoint, primarily in the right supplementary motor area, right middle temporal gyrus, right inferior parietal lobe, right postcentral gyrus and left posterior cingulate gyrus. Longitudinal results demonstrated that altered nodal characteristics were partially restored one month later. Additionally, significant correlations between the nodal characteristics of the right supplementary motor area and the clinical scale scores (FMA and NDS) were observed in stroke patients. Similar behavioral-neuroimaging correlations were found in the right inferior parietal lobe.ConclusionAltered topological properties may be an effect of stroke, which can be modulated during recovery. The longitudinal results and the neuroimaging-behavioral relationship may provide information for understanding brain recovery from stroke. Future studies should detect whether observed changes in structural topological properties can predict the recovery of daily cognitive function in stroke.

Project description:An intact orthographic processing system is critical for normal reading and spelling. Here we investigate the neural changes associated with impairment and subsequent recovery of the orthographic lexical processing system in an individual with an ischemic left posterior cerebral artery (PCA) stroke. This work describes a longitudinal case study of a patient, whose initials are MMY, with impairments in orthographic lexical processing for reading and spelling at stroke onset, and who recovered these skills within 1 year post stroke. We tested the hypothesis that this acute impairment to reading and spelling would be associated with a selective loss of neural activation in the left fusiform gyrus (FG), and that subsequent recovery would be associated with a gain of neural activation in this region. MMY's case provided a unique opportunity to assess the selectivity of neural changes because she demonstrated a behavioral recovery of naming as well; i.e., if there is neural recovery for reading and spelling, but not naming, then these neural changes are selective to the recovery of orthographic processing. To test our hypothesis, we examined longitudinal behavioral and functional magnetic resonance imaging (fMRI) data of reading, spelling, and visual object naming acquired acutely, 3 weeks, 5 months, and one year post stroke. In confirmation of our hypothesis, the loss and subsequent gain of orthographic lexical processing was associated with up-regulation of neural activation in areas previously associated with orthographic lexical processing: i.e., the left mid-FG and inferior frontal junction (IFJ). Furthermore, these neural changes were found to be selective to orthographic processing, as they were observed for reading and spelling, but not for visual object naming within the left mid-FG. This work shows that left PCA stroke can temporarily and selectively disrupt the orthographic lexical processing system, not only in the posterior region adjacent to the stroke, but also in relatively distant frontal orthographic processing regions.

Project description:Background:Improving our knowledge about the impact of restorative therapies employed in the rehabilitation of a stroke patient may help guide practitioners in prescribing treatment regimen that may lead to better post-stroke recovery and quality of life. Aims:To evaluate the neurological and functional recovery for 3 months after an acute ischemic stroke occurred within previous 3 months. To determine predictors of recovery. Design:Prospective observational registry. Population. Patients having suffered acute moderate to severe ischemic stroke of moderate to severe intensity within the previous 3 months with National Institutes of Health Stroke Scale (NIHSS) score from 10 to 20, 24 hours after arrival at emergency room (ER). Methods:All prespecified variables (sociodemographic and clinical data, lifestyle recommendations, rehabilitation prescription, and neurological assessments) were assessed at three visits, i.e., baseline (D0), one month (M1), and three months (M3). Results:Out of 143 recruited patients, 131 could be analysed at study entry within 3 months after stroke onset with a mean acute NIHSS score of 14.05, decreased to 10.8 at study baseline. Study sample was aged 64.9 ± 13.8?years, with 49.2% of women. Neurorehabilitation treatment was applied to 9 of 10 patients from the acute phase and for three months with different intensities depending on the centre. A large proportion of patients recovered from severe dependency on activities of daily living (ADL) at D0 to a mild or moderate disability requiring some help at M3: mean NIHSS = 10.8?to?5.7; median?modified?Rankin?Scale?(mRS) = 4?to?3; Barthel?index?(BI) = 40?to?70; all p?values < 0.001. Multivariate analyses integrating other regression variables showed a trend in favour of rehabilitation and revascularization therapies on recovery although did not reach statistical significance and that the positive predictors of recovery improvement were baseline BI score, time to treatment, and dietary supplement MLC901 (NurAiD™II). A larger percentage of patients with more severe stroke (NIHSS > 14) who received MLC901 showed above median improvements on mRS compared to control group at M1 (71.4% vs. 29.4%; p = 0.032) and M3 (85.7% vs. 50%; p = 0.058). Older subjects and women tend to have less improvement by M3. Conclusions:Our study in patients with moderate to severe stroke shows overall recovery on neurological and functional assessments during the 3 months of study observation. Apart from demonstrating traditional "non-modifiable" predictors of outcome after stroke, like age, sex, and stroke severity, we also detected association between the use of dietary supplement MLC901 and recovery.

Dataset Information

Recovery of slow-5 oscillations in a longitudinal study of ischemic stroke patients.

Publications

Recovery of slow-5 oscillations in a longitudinal study of ischemic stroke patients.

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