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fMRI study of language. (Paradigm was antonym word generation from visual cues). A and B, Patient had a large susceptibility artifact, as evident on the SIM in B, due to dental braces. On the basis of the images in A, three readers considered frontal language dominance indeterminate and one fellow reader considered it right. Two staff readers considered posterior language dominance indeterminate , one fellow reader considered it right, and one fellow considered it mixed. After viewing the mask SIM, all four readers considered both frontal and posterior language dominance indeterminate. C, Prior fMRIs obtained before the placement of dental braces clearly demonstrate left dominance for language.
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The purpose of this study was to determine the incidence of susceptibility artifacts on functional MR imaging (fMRI) studies and their effect on fMRI readings. We hypothesized that the availability of the signal intensity maps (SIMs) changes the interpretation of fMRI studies in which susceptibility artifacts affected eloquent brain regions.
We rev...
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Context 1
... less-experi- enced readers 3 and 4, reader 3 changed 12 answers affecting nine patients (35%), and reader 4 changed 15 answers affecting 10 patients (38%) when the reading was made with the SIM in the 26 patients reviewed. The questions and answers changed by the readers 3 and 4 (fellows) when provided with the SIM are detailed in Table 4. Example cases are shown in Figures 3 and 4. ...
Citations
... These lesions' images were included in the fMRI statistical analyses using the Clinical Toolbox for SPM (Brett, Leff, Rorden, & Ashburner, 2001;Rorden, Bonilha, Fridriksson, Bender, & Karnath, 2012) that we adapted to work with SPM12. This step (see details below) prevented from adding artefacts to the results, which are often observed in patients with brain lesions (Strigel et al., 2005). ...
... For each patient, a mask based on the lesion image obtained by the Clinical toolbox for SPM (Brett et al., 2001;Rorden et al., 2012) was used to remove damaged areas in our patients from the statistical analyses. Those steps allowed us to prevent the contamination of the results by artefacts that are often observed in patients with brain lesions (Strigel et al., 2005). The realignment parameters were included in the model as regressors and contrasts of interest were specified for both sessions in the same design. ...
Prismatic adaptation has been repeatedly reported to alleviate neglect symptoms; in normal subjects, it was shown to enhance the representation of the left visual space within the left inferior parietal cortex. Our study aimed to determine in humans whether similar compensatory mechanisms underlie the beneficial effect of prismatic adaptation in neglect. Fifteen patients with right hemispheric lesions and 11 age-matched controls underwent a prismatic adaptation session which was preceded and followed by fMRI using a visual detection task. In patients, the prismatic adaptation session improved the accuracy of target detection in the left and central space and enhanced the representation of this visual space within the left hemisphere in parts of the temporal convexity, inferior parietal lobule and prefrontal cortex. Across patients, the increase in neuronal activation within the temporal regions correlated with performance improvements in this visual space. In control subjects, prismatic adaptation enhanced the representation of the left visual space within the left inferior parietal lobule and decreased it within the left temporal cortex. Thus, a brief exposure to prismatic adaptation enhances, both in patients and in control subjects, the competence of the left hemisphere for the left space, but the regions extended beyond the inferior parietal lobule to the temporal convexity in patients. These results suggest that the left hemisphere provides compensatory mechanisms in neglect by assuming the representation of the whole space within the ventral attentional system. The rapidity of the change suggests that the underlying mechanism relies on uncovering pre-existing synaptic connections.
... We anticipated that the approach used here will be sensitive to the network changes associated the early recovery window in TBI. Moreover, in studies using fMRI to examine neurotrauma there is concern regarding the influence of brain lesions on the BOLD signal [30] and this is particularly problematic in local areas of hemorrhage where blood products cause susceptibility artifact and local signal attenuation [31][32]. However, the ICA procedure implemented here can isolate the effects of local signal drop-out as a ''component'' and model these data or remove the signal during ''denoising and nuisance'' identification. ...
There remains much unknown about how large-scale neural networks accommodate neurological disruption, such as moderate and severe traumatic brain injury (TBI). A primary goal in this study was to examine the alterations in network topology occurring during the first year of recovery following TBI. To do so we examined 21 individuals with moderate and severe TBI at 3 and 6 months after resolution of posttraumatic amnesia and 15 age- and education-matched healthy adults using functional MRI and graph theoretical analyses. There were two central hypotheses in this study: 1) physical disruption results in increased functional connectivity, or hyperconnectivity, and 2) hyperconnectivity occurs in regions typically observed to be the most highly connected cortical hubs, or the "rich club". The current findings generally support the hyperconnectivity hypothesis showing that during the first year of recovery after TBI, neural networks show increased connectivity, and this change is disproportionately represented in brain regions belonging to the brain's core subnetworks. The selective increases in connectivity observed here are consistent with the preferential attachment model underlying scale-free network development. This study is the largest of its kind and provides the unique opportunity to examine how neural systems adapt to significant neurological disruption during the first year after injury.
... Human vision is divided into central and peripheral vision [7]. Peripheral vision has mostly been characterized in terms of the reductions in resolution or contrast sensitivity as eccentricity increases [41][42][43]. The ability of humans to detect movement is better in peripheral vision than foveal vision, but color discrimination is markedly worse [44,45]. ...
In human visual cortex, the primary visual cortex (V1) is considered to be essential for visual information processing; the fusiform face area (FFA) and parahippocampal place area (PPA) are considered as face-selective region and places-selective region, respectively. Recently, a functional magnetic resonance imaging (fMRI) study showed that the neural activity ratios between V1 and FFA were constant as eccentricities increasing in central visual field. However, in wide visual field, the neural activity relationships between V1 and FFA or V1 and PPA are still unclear. In this work, using fMRI and wide-view present system, we tried to address this issue by measuring neural activities in V1, FFA and PPA for the images of faces and houses aligning in 4 eccentricities and 4 meridians. Then, we further calculated ratio relative to V1 (RRV1) as comparing the neural responses amplitudes in FFA or PPA with those in V1. We found V1, FFA, and PPA showed significant different neural activities to faces and houses in 3 dimensions of eccentricity, meridian, and region. Most importantly, the RRV1s in FFA and PPA also exhibited significant differences in 3 dimensions. In the dimension of eccentricity, both FFA and PPA showed smaller RRV1s at central position than those at peripheral positions. In meridian dimension, both FFA and PPA showed larger RRV1s at upper vertical positions than those at lower vertical positions. In the dimension of region, FFA had larger RRV1s than PPA. We proposed that these differential RRV1s indicated FFA and PPA might have different processing strategies for encoding the wide field visual information from V1. These different processing strategies might depend on the retinal position at which faces or houses are typically observed in daily life. We posited a role of experience in shaping the information processing strategies in the ventral visual cortex.
Test the hypothesis about the potential role of functional MRI (fMRI) to evaluate the plasticity of the cortical motor areas in patients with brains tumors and brain arteriovenous malformations (AVMs) and measurement of the lesion-to-fMRI activation distance for predicting risk of new motor deficit after surgery.
This was a retrospective study. The present study population enrolled eight patients with motor cortex lesions. Cortical motor representations were mapped in these patients harboring tumor or AVMs occupying the region of primary motor cortex (M1). Five patients had known diagnosis of primary brain tumor including glioblastoma multiforme, (n = 1), diffuse astrocytoma (n = 2), dysembryoplastic neuroepithelial tumor (DNET) (n = 1) and unknown pathology (n = 1). Three patients had known diagnosis of brain AVMs. Three patients showed hemiparesis at the time of presentation. Focal/generalized seizure or headache was present in the remaining patients. Simple movements of both hands were performed Localization of the activation in the affected hemisphere was compared with that in the unaffected hemisphere and evaluated with respect to the normal M1 somatotopic organization. Distance between the location of the fMRI activation (M1) and margin of the lesion was recorded.
Cortical activation was found in two patterns: 1) functional displacement within affected M1 independent of the structural distortion induced by the tumor or AVMs (n = 7) and 2) presence of activation within the non-primary motor cortex without activation in the affected or unaffected M1 (n = 1).
Brain tumor or AVMs led to reorganization within the somatotopic affected M1 and can expand into non-primary motor cortex area. Distortion of the anatomy alone by the space-taking lesion did not influence the location of the reorganized cortex. No particular type of reorganization pattern could be predicted fMRI could be localized reorganized cortex and was found to be a useful tool to assess the lesion-to-activation distance for predicting risk of new motor deficit after surgery. The present study thus emphasizes the importance of considering additional fMRI with structural MRI to evaluate individual differences in cortical plasticity for treatment planning, particularly in the neurosurgical procedure.
