Simultaneous multislice Echo Planar Imaging (EPI) acquisition using parallel imaging can decrease the acquisition time for diffusion imaging and allow full-brain, high-resolution functional MRI (fMRI) acquisitions at a reduced repetition time (TR). However, the unaliasing of simultaneously acquired, closely spaced slices can be difficult, leading to a high g-factor penalty. We introduce a method to create interslice image shifts in the phase encoding direction to increase the distance between aliasing pixels.
Recurrent anticipation of ominous events is central to obsessions, the core symptom of obsessive-compulsive disorder (OCD), yet the neural basis of intrinsic anticipatory processing in OCD is unknown. We studied nonmedicated adults with OCD and case matched healthy controls in a visual-spatial working memory task with distractor. Magnetoencephalography was used to examine the medial cortex activity during anticipation of to-be-inhibited distractors and to-be-facilitated retrieval stimuli.
The Performance Dip is a newly characterized behavioral phenomenon, where, paradoxically, a weaker task-irrelevant visual stimulus causes larger disturbances on the accuracy of a main letter identification task than a stronger stimulus does. Understanding mechanisms of the Performance Dip may provide insight into unconsciousness behavior. Here, we investigated the generalization of the Performance Dip.
BACKGROUND: . Somatosensory input to the motor cortex may play a critical role in motor relearning after hemiparetic stroke.
OBJECTIVE: . The authors tested the hypothesis that motor recovery after hemiparetic stroke relates to changes in responsiveness of the sensorimotor cortex (SMC) to somatosensory input.
METHODS: . A total of 10 hemiparetic stroke patients underwent serial functional magnetic resonance imaging (fMRI) during tactile stimulation and testing of sensorimotor function over 1 year-at early subacute, late subacute, and chronic poststroke time points.
Near-Infrared Spectroscopy (NIRS) measures the functional hemodynamic response occurring at the surface of the cortex. Large pial veins are located above the surface of the cerebral cortex. Following activation, these veins exhibit oxygenation changes but their volume likely stays constant. The back-reflection geometry of the NIRS measurement renders the signal very sensitive to these superficial pial veins. As such, the measured NIRS signal contains contributions from both the cortical region as well as the pial vasculature.
Near-infrared spectroscopy (NIRS) signals have been shown to correlate with resting-state BOLD-fMRI data across the whole brain volume, particularly at frequencies below 0.1Hz. While the physiological origins of this correlation remain unclear, its existence may have a practical application in minimizing the background physiological noise present in BOLD-fMRI recordings. We performed simultaneous, resting-state fMRI and 28-channel NIRS in seven adult subjects in order to assess the utility of NIRS signals in the regression of physiological noise from fMRI data.
The abnormal vasculature of the tumor microenvironment supports progression and resistance to treatment. Judicious application of antiangiogenic therapy may normalize the structure and function of the tumor vasculature, promoting improved blood perfusion. However, direct clinical evidence is lacking for improvements in blood perfusion after antiangiogenic therapy. In this study, we used MRI to assess tumor blood perfusion in 30 recurrent glioblastoma patients who were undergoing treatment with cediranib, a pan-VEGF receptor tyrosine kinase inhibitor.
Entorhinal cortex displays a distinctive organization in layer II and forms small elevations on its surface called entorhinal verrucae. In Alzheimer's disease, the verrucae disappear due to neurofibrillary tangle formation and neuronal death. Isosurface models were reconstructed from high-resolution ex vivo MRI volumes scanned at 7.0 T and individual verruca were measured quantitatively for height, width, volume, and surface area on control and mild Alzheimer's cases.
Late-onset Alzheimer's disease (AD) is 50-70% heritable with complex genetic underpinnings. In addition to Apoliprotein E (APOE) ε4, the major genetic risk factor, recent genome-wide association studies (GWAS) have identified a growing list of sequence variations associated with the disease. Building on a prior large-scale AD GWAS, we used a recently developed analytic method to compute a polygenic score that involves up to 26 independent common sequence variants and is associated with AD dementia, above and beyond APOE.
Deviation of dopamine homeostasis is known to be associated with disorders like drug addiction and Parkinson's disease. As dopamine function is tightly regulated within the basal ganglia circuitry, cortical perturbation would lead to modulation of dopaminergic activity in the striatum. We proposed and tested if somatosensory activity such as forepaw stimulation could modulate dopaminergic function.
