Working Memory in Patients with Mild Traumatic Brain Injury: Functional MR Imaging Analysis

Article · July 2012with67 Reads
DOI: 10.1148/radiol.12112154 · Source: PubMed
Abstract
To analyze brain activation patterns in response to tests of working memory after a mild traumatic brain injury (MTBI). Research ethics committee approval and patient written informed consent were obtained. Brain activation patterns in response to n-back working memory tasks (n = 1, 2, 3) were assessed with functional magnetic resonance (MR) imaging in 20 patients with MTBI within 1 month after their injury and in 18 healthy control subjects. In n-back working memory tasks, participants monitored a series of number stimuli and were to indicate when the presented number was the same as that presented n back previously. Nine (45%) MTBI patients underwent follow-up functional MR imaging studies 6 weeks later. Digit span, a memory test for how many numbers a person can remember in sequence, and continuous performance test (CPT), a test that measures a person's sustained and selective attention and impulsivity, were also performed before functional MR imaging studies and outside the imager for each participant. Clinical data were analyzed by using t and χ(2) tests. Within-group, between-group, and initial and follow-up differences of functional MR imaging data were analyzed by using one-sample, two-sample, and paired t tests, respectively. Groups were similar for sex (P = .75), years of education (P = .069), digit span (P = .37 for total score), CPT (P = .31, .27, and .43 for omission error, commission error, and hit reaction time, respectively), and accuracy of n-back working memory performance (P = .90, .11, and .39 for one-, two-, and three-back tasks, respectively). Brain activation patterns differed between MTBI patients and controls in response to increasing working memory loads (P < .01, uncorrected). Control subjects maintained their ability to increase activation in the working memory circuitry with each increase in working memory load. In contrast, MTBI patients were impaired in their ability to increase activation in working memory circuitry under both moderate and high working memory load conditions. However, MTBI patients did show cerebral plasticity, as evidenced by more activation in some areas outside and inside the working memory circuitry as compared with control subjects (P < .01, uncorrected). In the 6-week follow-up study, compared with baseline, MTBI patients showed an improvement of activation in response to increasing working memory loads (P < .05, uncorrected). MTBI-induced differences in working memory functional activity were observed even though differences in behavioral performance between MTBI patients and controls were absent, which suggests that this approach may increase sensitivity to MTBI compared with neuropsychological evaluation alone.
5 Figures
    • Therefore, an investigation of the brain's functional activity is also important for a further understanding of brain alterations. Task-based fMRI demonstrates functional alterations of mTBI patients' memory (Chen et al., 2012; McAllister et al., 1999) and language (Morgan et al., 2013; Tivarus et al., 2012) networks. Though task-based fMRI has been used to identify activity related to specific brain regions for years (Ogawa et al., 1992), functional brain activity is more complicated than is disclosed by investigating the brain during tasks.
    [Show abstract] [Hide abstract] ABSTRACT: Mild traumatic brain injury (mTBI) accounts for over one million emergency visits each year in the United States. The large-scale structural and functional network connectivity changes of mTBI are still unknown. This study was designed to determine the connectome-scale brain network connectivity changes in mTBI at both structural and functional levels. 40 mTBI patients at the acute stage and 50 healthy controls were recruited. A novel approach called Dense Individualized and Common Connectivity-based Cortical Landmarks (DICCCOLs) was applied for connectome-scale analysis of both diffusion tensor imaging and resting state functional MRI data. Among 358 networks identified on DICCCOL analysis, 41 networks were identified as structurally discrepant between patient and control groups. The involved major white matter tracts include the corpus callosum, and superior and inferior longitudinal fasciculi. Functional connectivity analysis identified 60 connectomic signatures that differentiate patients from controls with 93.75% sensitivity and 100% specificity. Analysis of functional domains showed decreased intra-network connectivity within the emotion network and among emotion-cognition interactions, and increased interactions among action-emotion and action-cognition as well as within perception networks. This work suggests that mTBI may result in changes of structural and functional connectivity on a connectome scale at the acute stage.
    Full-text · Article · Jun 2016
    • Summarizing across tasks, the data presented here suggest that participants with mTBI and ongoing PCS have limited working memory capacity (lower BOLD increase in left IFG/MFG), and compensate for this by greater attention and performance monitoring (greater BOLD increase in ACC) and reduction of activity in task-irrelevant areas (medial temporal lobe and DMN). These functional changes are observed even in the absence of behavioral differences (Fig. 3), as has been seen in previous studies (McAllister et al. 2001; Stulemeijer et al. 2010; Witt et al. 2010; Chen et al. 2012) indicating that fMRI may be more sensitive to subtle changes after mTBI. It has previously been suggested that a large scale disorder of attention underlies the symptoms seen after TBI (Ghajar and Ivry 2008), with enhanced top-down control of attention necessary to compensate for microstructural damage causing variability in white matter transmission speed.
    [Show abstract] [Hide abstract] ABSTRACT: Persistent postconcussion syndrome (PCS) occurs in around 5-10% of individuals after mild traumatic brain injury (mTBI), but research into the underlying biology of these ongoing symptoms is limited and inconsistent. One reason for this could be the heterogeneity inherent to mTBI, with individualized injury mechanisms and psychological factors. A multimodal imaging study may be able to characterize the injury better. To look at the relationship between functional (fMRI), structural (diffusion tensor imaging), and metabolic (magnetic resonance spectroscopy) data in the same participants in the long term (>1 year) after injury. It was hypothesized that only those mTBI participants with persistent PCS would show functional changes, and that these changes would be related to reduced structural integrity and altered metabolite concentrations. Functional changes associated with persistent PCS after mTBI (>1 year postinjury) were investigated in participants with and without PCS (both n = 8) and non-head injured participants (n = 9) during performance of working memory and attention/processing speed tasks. Correlation analyses were performed to look at the relationship between the functional data and structural and metabolic alterations in the same participants. There were no behavioral differences between the groups, but participants with greater PCS symptoms exhibited greater activation in attention-related areas (anterior cingulate), along with reduced activation in temporal, default mode network, and working memory areas (left prefrontal) as cognitive load was increased from the easiest to the most difficult task. Functional changes in these areas correlated with reduced structural integrity in corpus callosum and anterior white matter, and reduced creatine concentration in right dorsolateral prefrontal cortex. These data suggest that the top-down attentional regulation and deactivation of task-irrelevant areas may be compensating for the reduction in working memory capacity and variation in white matter transmission caused by the structural and metabolic changes after injury. This may in turn be contributing to secondary PCS symptoms such as fatigue and headache. Further research is required using multimodal data to investigate the mechanisms of injury after mTBI, but also to aid individualized diagnosis and prognosis.
    Full-text · Article · Feb 2015
    • Traumatic Brain Injury (TBI) is the most common worldwide neurologic condition, with an incidence of 235-556/100000, and more than 75% of TBIs are classified as mild traumatic brain injury (mTBI) by definition of the American Congress of Rehabilitative Medicine[1][2][3]. By definition, a patient of mTBI is a person who has had a traumatically induced physiological disruption of brain function, but where the severity of the injury does not exceed the following: loss of consciousness (LOC) of approximately 30 minutes or less, Glasgow Coma Scale (GCS) score of 13 to15 upon acute medical evaluation, and post-traumatic amnesia (PTA) less than 24 hours in duration[4].
    [Show abstract] [Hide abstract] ABSTRACT: Mild traumatic brain injury (mTBI) is a large subgroup of traumatic brain injury in which patients experience minor but persistent neurophysiologic dysfunctions that lead to disability in social interaction and daily work. New emerging magnetic resonance imaging (MRI) techniques hope to provide better understanding of the underlying pathophysiology of various symptoms in mTBI. Susceptibility-weighted MRI (SWMRI) is a MRI technique particularly sensitive in detecting cerebral microbleeds (CMBs) in the brain parenchyma. Studies have shown evidence of CMBs associated with mTBI, particularly at gray-white matter junction. Although the significance of CMBs has been debated in recent years, there are evidences that these subtle image findings may have diagnostic and prognostic implications, and possibly an imaging biomarker in mTBI. SWMRI is recommended as complementary sequence to the MRI protocol for patients with mTBI for detection of CMBs as well as for further evaluate the severity of injury and future treatment planning.
    Article · Jan 2015 · Evidence-based Complementary and Alternative Medicine
    • The most intriguing results of our study are those derived from the parametric analysis of attention network activation, which demonstrated an impaired ability of ABI patients to increase the recruitment of several regions of the network (mainly located in the occipital lobes, cerebellum, and thalamus ) with increasing task demand. These findings are in agreement with previous fMRI studies of the working memory network in adult and pediatric TBI patients678910, pointing towards a global impairment of functional reserve (not specifically limited to a given cognitive network) in patients suffering of this condition. Such an impaired functional reserve exerts an impact on the clinical outcome of these patients, since it was correlated with a worse score at FIM and longer RT at CCPT.
    [Show abstract] [Hide abstract] ABSTRACT: Introduction: To assess abnormalities of fMRI activity during a sustained attention task in pediatric patients with traumatic brain injury (TBI). Methods: FMRI scans were acquired from 22 pediatric TBI patients (mean age=14.3 years; mean time from TBI=1.96 years) and 7 healthy controls (mean age=10.8 years) during the administration of the Conners’ CPT. Patients underwent the Wechsler Intelligence Scale for Children (WISC-IV) and the Functional Independence Measure (FIM) evaluation. Results: In both groups, significant activations during the different conditions of the CPT task were found in the right somatosensory cortex, supplementary motor area, middle cingulate cortex, inferior frontal gyrus (pars opercularis) and left cerebellum. With increasing task difficulty (“load effect”) both groups had increased fMRI activity in the bilateral middle occipital gyrus. During this condition, compared to TBI patients, controls also had an increased recruitment of the middle occipital gyrus as well as temporal and parietal regions. Patients having better performances at the CPT, better scores at WISC-IV and FIM scales and a longer time from TBI showed a reduced activity of the anterior cingulate cortex, superior frontal and middle frontal gyri during the CPT task. Patients having better scores at WISC-IV and a longer time from TBI showed also higher activity of frontal and temporal regions during the “load” condition. Conclusions: Pediatric TBI patients experience an inability to optimize the recruitment of the attentional network, which might contribute to explain the attentional deficits frequently observed in this condition.
    Full-text · Conference Paper · May 2014
    • Improvements in balance and, to a lesser extent, in gait outcomes were also found in these two patients. In another study of 20 patients at 1 month after mild TBI (mTBI) and 18 healthy controls, Chen et al. (2012) demonstrated that brain activation patterns differed between mTBI patients and controls in response to increasing working memory loads (P < 0.01, uncorrected). mTBI patients were impaired in their ability to increase activation in working memory circuitry under both moderate and high working memory load conditions in contrast with controls.
    [Show abstract] [Hide abstract] ABSTRACT: The brain is highly plastic after stroke or epilepsy; however, there is a paucity of brain plasticity investigation after traumatic brain injury (TBI). This mini review summarizes the most recent evidence of brain plasticity in human TBI patients from the perspective of advanced magnetic resonance imaging. Similar to other forms of acquired brain injury, TBI patients also demonstrated both structural reorganization as well as functional compensation by the recruitment of other brain regions. However, the large scale brain network alterations after TBI are still unknown, and the field is still short of proper means on how to guide the choice of TBI rehabilitation or treatment plan to promote brain plasticity. The authors also point out the new direction of brain plasticity investigation.
    Full-text · Article · Apr 2014
    • It causes 1.1 million emergency visits, 235,000 hospitalisations, and 50,000 deaths in the United States every year [5, 6]. The socioeconomic impacts and burden of diseases for disability following TBI are potentially long term or lifelong [2–5, 7–14]. While the epidemiology, natural history, risk factors, and outcomes of TBI have been established [1–17], TBI treatment and rehabilitation are still crucial problems of global concern.
    [Show abstract] [Hide abstract] ABSTRACT: Background. Little research exists on acupuncture treatment's effect on patients with traumatic brain injury (TBI). Methods. Using Taiwan's National Health Insurance Research Database, we conducted a cohort study to compare the use of emergency care and hospitalization in TBI patients with and without acupuncture treatment in the first year after TBI. The adjusted relative risks (RRs) and 95% confidence intervals (CIs) of high use of emergency care and hospitalization associated with acupuncture treatment were calculated in multivariate Poisson regression models with generalized estimating equation. Results. The means of medical visits of emergency care and hospitalization were lower in TBI patients with acupuncture treatment than in those without acupuncture treatment. After adjustment, acupuncture treatment was associated with decreased risk of high emergency care visits (beta = -0.0611, P = 0.0452) and hospitalization (beta = -0.0989, P < 0.0001). The RRs of high medical visits and expenditure for hospitalization associated with acupuncture treatment were 0.62 (95% CI = 0.50-0.76) and 0.66 (95% CI = 0.53-0.83), respectively. Conclusion. Patients with TBI who receive acupuncture treatment have reduced the use of emergency care and hospitalization in the first year after injury. The mechanisms of effects of acupuncture on TBI warrant further investigations.
    Full-text · Article · Jul 2013
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