Weiwei Men

Acute Aerobic Exercise Increases Cortical Activity during Working Memory: A Functional MRI Study in Female College Students

There is increasing evidence that acute aerobic exercise is associated with improved cognitive function. However, neural correlates of its cognitive plasticity remain largely unknown. The present study examined the effect of a session of acute aerobic exercise on working memory task-evoked brain activity as well as task performance. A within-subjects design with a counterbalanced order was employed. Fifteen young female participants (M = 19.56, SD = 0.81) were scanned using functional magnetic resonance imaging while performing a working memory task, the N-back task, both following an acute exercise session with 20 minutes of moderate intensity and a control rest session. Although an acute session of exercise did not improve behavioral performance, we observed that it had a significant impact on brain activity during the 2-back condition of the N-back task. Specifically, acute exercise induced increased brain activation in the right middle prefrontal gyrus, the right lingual gyrus, and the left fusiform gyrus as well as deactivations in the anterior cingulate cortexes, the left inferior frontal gyrus, and the right paracentral lobule. Despite the lack of an effect on behavioral measures, significant changes after acute exercise with activation of the prefrontal and occipital cortexes and deactivation of the anterior cingulate cortexes and left frontal hemisphere reflect the improvement of executive control processes, indicating that acute exercise could benefit working memory at a macro-neural level. In addition to its effects on reversing recent obesity and disease trends, our results provide substantial evidence highlighting the importance of promoting physical activity across the lifespan to prevent or reverse cognitive and neural decline.

Patterns in Cortical Connectivity for Determining Outcomes in Hand Function after Subcortical Stroke

Background and Purpose Previous studies have noted changes in resting-state functional connectivity during motor recovery following stroke. However, these studies always uncover various patterns of motor recovery. Moreover, subgroups of stroke patients with different outcomes in hand function have rarely been studied. Materials and Methods We selected 24 patients who had a subcortical stroke in the left motor pathway and displayed only motor deficits. The patients were divided into two subgroups: completely paralyzed hands (CPH) (12 patients) and partially paralyzed hands (PPH) (12 patients). Twenty-four healthy controls (HC) were also recruited. We performed functional connectivity analysis in both the ipsilesional and contralesional primary motor cortex (M1) to explore the differences in the patterns between each pair of the three diagnostic groups. Results Compared with the HC, the PPH group displays reduced connectivity of both the ipsilesional and contralesional M1 with bilateral prefrontal gyrus and contralesional cerebellum posterior lobe. The connectivity of both the ipsilesional and contralesional M1 with contralateral primary sensorimotor cortex was reduced in the CPH group. Additionally, the connectivity of the ipsilesional M1 with contralesional postcentral gyrus, superior parietal lobule and ipsilesional inferior parietal lobule was reduced in the CPH group compared with the PPH group. Moreover, the connectivity of these regions was positively correlated with the Fugl-Meyer Assessment scores (hand+wrist) across all stroke patients. Conclusions Patterns in cortical connectivity may serve as a potential biomarker for the neural substratum associated with outcomes in hand function after subcortical stroke.

The corpus callosum of Albert Einstein‘s brain: another clue to his high intelligence?

Sir, Albert Einstein was arguably the greatest physicist in the 20th century and his extraordinary intelligence has long intrigued both scientists and the general public. Despite several studies that focused mainly on the histological and morphological features of Einstein’s brain after his death, the substrates of Einstein’s genius are still a mystery (Diamond et al. , 1985; Anderson and Harvey, 1996; Kigar et al. , 1997; Hines, 1998; Witelson et al. , 1999 a , b ; Colombo et al. , 2006; Falk, 2009). Recently, Falk et al. (2013) analysed 14 newly discovered photographs and found that Einstein’s brain had an extraordinary prefrontal cortex, and that inferior portions of the primary somatosensory and motor cortices were greatly expanded in the left hemisphere. Among these 14 images were photographs of the left and right medial surface of Einstein’s brain, on which the corpus callosum was shown with great resolution and accuracy. The corpus callosum is the largest nerve fibre bundle that connects the cortical regions of the cerebral hemispheres in human brains and it plays an essential role in the integration of information transferred between the hemispheres over thousands of axons (Aboitiz et al. , 1992). The two photographs of the medial surfaces of Einstein’s cerebral hemispheres provide the basis for the present study. To examine whether there are regional callosal differences between the brain of Einstein and those of ordinary people, and to minimize potential differences in corpus callosum morphology due to cause of death, brain atrophy, age, and sex, in vivo MRI data sets from two different age groups were used. The high-resolution photographs of Einstein’s left and right hemispheres were supplied by Dean Falk with permission from the National Museum of Health and Medicine (Fig. 1). Because Einstein was right-handed and died at …

Functional reorganization associated with outcome in hand function after stroke revealed by regional homogeneity

IntroductionPrevious studies of task-based functional neuroimaging have shown that various patterns of functional reorganization underlie motor recovery following stroke. However, the mechanisms underlying functional reorganization that contribute to outcome differences in hand function after stroke have not been completely characterized. We, for the first time, investigate subgroups of stroke patients with different outcomes in hand function using a resting-state fMRI approach.MethodsWe selected 24 patients with subcortical stroke and divided them into two subgroups: completely paralyzed hands (CPH, 12 patients) and partially paralyzed hands (PPH, 12 patients). Twenty-four healthy controls (HCs) matched for age and handedness were also recruited. We used regional homogeneity (ReHo) method to map regional spontaneous activity across the whole brain and performed a two-sample t test between each pair of the three diagnostic groups.ResultsCompared to HCs, we found increased ReHo in the ipsilesional hemisphere in PPH and, conversely, increased ReHo in the contralesional hemisphere in CPH. Moreover, we detected decreased ReHo in the ipsilesional primary sensorimotor cortex and superior temporal gyrus, in addition to increased ReHo in the contralesional premotor cortex and ipsilesional medial frontal gyrus in CPH compared to PPH. Additionally, the ReHo index of these regions significantly correlated with the Fugl-Meyer assessment scores (hand + wrist) across all stroke patients.ConclusionsOur study offers a new insight into relationships between functional reorganization and outcomes in hand function after subcortical stroke, and the ReHo method can provide an effective tool for evaluating the efficiency of rehabilitative therapies following stroke.

Altered topological properties of the cortical motor-related network in patients with subcortical stroke revealed by graph theoretical analysis

Cerebral neuroplasticity after stroke has been elucidated by functional neuroimaging. However, little is known concerning how topological properties of the cortical motor‐related network evolved following subcortical stroke. In the present study, we investigated 24 subcortical stroke patients with only left motor pathway damaged and 24 matched healthy controls. A cortical motor‐related network consisting of 20 brain regions remote from the primary lesion was constructed using resting‐state functional MRI datasets. We subsequently used graph theoretical approaches to analyze the topological properties of this network in both stroke patients and healthy controls. In addition, we divided the stroke patients into two subgroups according to their outcomes in hand function to explore relationships between topological properties of this network and outcomes in hand function. Although we observed that the cortical motor‐related network in both healthy controls and stroke patients exhibited small‐world topology, the local efficiency of this network in stroke patients is higher than and global efficiency is lower than those in healthy controls. In addition, striking alterations in the betweenness centrality of regions were found in stroke patients, including the contralesional supplementary motor area, dorsolateral premotor cortex, and anterior inferior cerebellum. Moreover, we observed significant correlations between betweenness centrality of regions and Fugl‐Meyer assessment scores. A tendency for the cortical motor‐related network to be close to a regular configuration and altered betweenness centrality of regions were demonstrated in patients with subcortical stroke. This study provided insight into functional organization after subcortical stroke from the viewpoint of network topology. Hum Brain Mapp 35:3343–3359, 2014.

Secondary Degeneration Detected by Combining Voxel-Based Morphometry and Tract-Based Spatial Statistics in Subcortical Strokes with Different Outcomes in Hand Function

BACKGROUND AND PURPOSE: Secondary degeneration of the pyramidal tract after focal motor pathway stroke has been observed by diffusion tensor imaging. However, the relationships between outcomes in hand function and secondary degeneration in widespread regions are not well understood. For the first time, we investigated the differences of secondary degeneration across the whole brain between subgroups of patients with stroke. MATERIALS AND METHODS: We selected 23 patients who had a subcortical stroke in the left motor pathway and displayed only motor deficits. The patients were divided into 2 subgroups: CPH (11 patients) and PPH (12 patients). Twelve healthy controls matched for age and handedness were also recruited. We used both optimized VBM and TBSS to explore differences of FA across the whole brain between CPH and PPH. Furthermore, ROI analysis was carried out in the identified regions detected by VBM analysis to further quantify the degree of secondary degeneration in the CPH and PPH and compare these with healthy controls. RESULTS: Compared with PPH, FA was significantly decreased in the CPH in widespread regions of the motor system remote from the primary lesion, including the ipsilesional brain stem, medial frontal gyrus, precentral gyrus, superior temporal gyrus, supplementary motor area, and contralesional postcentral gyrus. In addition, FA within these identified regions correlated with Fugl-Meyer Assessment scores (hand+wrist). CONCLUSIONS: This study suggests a potential biomarker for outcome differences in hand function after subcortical stroke.

A Magnetic Nanoparticle Stabilized Gas Containing Emulsion for Multimodal Imaging and Triggered Drug Release

ABSTRACTPurposeTo develop a multimodal imaging guided and triggered drug delivery system based on a novel emulsion formulation composed of iron oxide nanoparticles, nanoscopic bubbles, and oil containing drugs.MethodsIron oxide paramagnetic nanoparticles were synthesized and modified with surface conjugation of polyethylenimide (PEI) or Bovine Serum Albumin (BSA). Both particles were used to disperse and stabilize oil in water emulsions containing coumarin-6 as the model drug. Sulfur hexafluoride was introduced into the oil phase to form nanoscopic bubbles inside the emulsions. The resulted gas containing emulsions were evaluated for their magnetic resonance (MR) and ultrasound (US) imaging properties. The drug release profile triggered by ultrasound was also examined.ResultsWe have successfully prepared the highly integrated multi-component emulsion system using the surface modified iron oxide nanoparticles to stabilize the interfaces. The resulted structure had distinctive MR and US imaging properties. Upon application of ultrasound waves, the gas containing emulsion would burst and encapsulated drug could be released.ConclusionThe integrated emulsion formulation was multifunctional with paramagnetic, sono-responsive and drug-carrying characteristics, which may have potential applications for disease diagnosis and imaging guided drug release.

Investigating microbleeding in cerebral ischemia rats using susceptibility-weighted imaging

PURPOSE To detect the distribution and prevalence of cerebral microbleeding (CMB) in rats after acute ischemic stroke using susceptibility-weighted imaging (SWI). METHOD After middle cerebral artery occlusion, 3T MR scanning was performed on 10 rats at 4h and 24h after ischemia. T2-weighted images (T2WI), T2 maps and diffusion-weighted images (DWI) were generated to estimate the severity of the brain ischemia. The SWI data were used to analyze location counts, size and distribution of the CMBs. The brain injury was evaluated and determined by hematoxylin and eosin (H&E) staining. RESULT At 24h after onset of ischemia, 13 CMBs were found in seven of the nine ischemic rats, whereas only two CMBs were found at 4h after ischemia onset in one of the nine ischemic rats. All visible CMBs detected in the SWI data were located in the ischemic lateral cortex, with diameters ranging from 0.2 to 0.5mm. In addition, we observed thickened vessels near the CMBs in the ischemic hemisphere in the SWI minimum intensity projections that did not appear in the symmetrical regions on the contralateral hemisphere. Histopathological results confirmed the CMBs, and increased microvascular density was observed in the ipsilateral hemisphere. CONCLUSION SWI technique allows the detection of CMBs and the accompanying thickened vessels in vivo in a rat model of cerebral ischemia, which appear to be challenging tasks using T2WI and DTI. The results reported in this work provide a better understanding of the pathophysiological mechanism of acute stroke.

Failure in Cognitive Suppression of Negative Affect in Adolescents with Generalized Anxiety Disorder

Hyperactivity of limbic (e.g., amygdalar) responses to negative stimuli has been implicated in the pathophysiology of generalized anxiety disorder (GAD). Evidence has also suggested that even a simple cognitive task involving emotionally salient stimuli can modulate limbic and prefrontal neural activation. However, whether neural modulation of emotional stimulus processing in a cognitive task is defective in adolescents with GAD has not yet been investigated. In this study, 20 adolescents with GAD and 14 comparable healthy controls underwent event-related functional magnetic resonance imaging (fMRI) coupled with an emotional valence evaluation task. During the evaluation of negative versus neutral stimuli, we found significant activation of the right inferior frontal gyrus (IFG) in healthy controls, while the bilateral amygdala was activated in GAD patients. Between-group analyses showed dramatically reduced task-activation of the right IFG in GAD patients, and the magnitude of IFG activity negatively correlated with symptom severity. Psychophysiological interaction analysis further revealed significantly decreased functional interaction between right IFG and anterior cingulate cortex and ventromedial prefrontal cortex in GAD patients compared with healthy controls. Taken together, our findings show failure to suppress negative affect by recruiting a cognitive distraction in adolescents with GAD, providing new insights into the pathophysiology of GAD.