1,721,136 research outputs found
A fast and effecctive strategy for artifact identification and signal restoring with HARDI data
No full textThe impact of emotional valence and stimulus habituation on fMRI signal reliability during emotion generation
Full text linkBackground: The emotional domain is often impaired across many neurological diseases, for this reason it represents a relevant target of rehabilitation interventions. Functional changes in neural activity related to treatment can be assessed with functional MRI (fMRI) using emotion-generation tasks in longitudinal settings. Previous studies demonstrated that within-subject fMRI signal reliability can be affected by several factors such as repetition suppression, type of task and brain anatomy. However, the differential role of repetition suppression and emotional valence of the stimuli on the fMRI signal reliability and reproducibility during an emotion-generation task involving the vision of emotional pictures is yet to be determined.Methods: Sixty-two healthy subjects were enrolled and split into two groups: group A (21 subjects, test-retest reliability on same-day and with same-task-form), group B (30 subjects, test-retest reproducibility with 4-month-interval using two equivalent-parallel forms of the task). Test-retest reliability and reproducibility of fMRI responses and patterns were evaluated separately for positive and negative emotional valence conditions in both groups. The analyses were performed voxel-wise, using the general linear model (GLM), and via a region-of-interest (ROI)-based approach, by computing the intra-class correlation coefficient (ICC) on the obtained contrasts.Results: The voxel-wise GLM test yielded no significant differences for both conditions in reliability and repro-ducibility analyses. As to the ROI-based approach, across all areas with significant main effects of the stimuli, the reliability, as measured with ICC, was poor (<0.4) for the positive condition and ranged from poor to excellent (0.4-0.75) for the negative condition. The ICC-based reproducibility analysis, related to the comparison of two different parallel forms, yielded similar results.Discussion: The voxel-wise GLM analysis failed to capture the poor reliability of fMRI signal which was instead highlighted using the ROI-based ICC analysis. The latter showed higher signal reliability for negative valence stimuli with respect to positive ones. The implementation of two parallel forms allowed to exclude neural suppression as the predominant effect causing low signal reliability, which could be instead ascribed to the employment of different neural strategies to cope with emotional stimuli over time. This is an invaluable in-formation for a better assessment of treatment and rehabilitation effects in longitudinal studies of emotional neural processing
Artifact identification and signal restoring in HARDI data by using spherical harmonic model
No full textResting-state functional connectivity is modulated by cognitive reserve in early Parkinson’s disease
Full text linkBackgroundFronto-striatal disconnection is thought to be at the basis of dysexecutive symptoms in patients with Parkinson's disease (PD). Multiple reserve-related processes may offer resilience against functional decline. Among these, cognitive reserve (CR) refers to the adaptability of cognitive processes.ObjectiveTo test the hypothesis that functional connectivity of pathways associated with executive dysfunction in PD is modulated by CR.MethodsTwenty-six PD patients and 24 controls underwent resting-state functional magnetic resonance imaging. Functional connectivity was explored with independent component analysis and seed-based approaches. The following networks were selected from the outcome of the independent component analysis: default-mode (DMN), left and right fronto-parietal (l/rFPN), salience (SalN), sensorimotor (SMN), and occipital visual (OVN). Seed regions were selected in the substantia nigra and in the dorsolateral and ventromedial prefrontal cortex for the assessment of seed-based functional connectivity maps. Educational and occupational attainments were used as CR proxies.ResultsCompared with their counterparts with high CR, PD individuals with low CR had reduced posterior DMN functional connectivity in the anterior cingulate and basal ganglia, and bilaterally reduced connectivity in fronto-parietal regions within the networks defined by the dorsolateral and ventrolateral prefrontal seeds. Hyper-connectivity was detected within medial prefrontal regions when comparing low-CR PD with low-CR controls.ConclusionCR may exert a modulatory effect on functional connectivity in basal ganglia and executive-attentional fronto-parietal networks. In PD patients with low CR, attentional control networks seem to be downregulated, whereas higher recruitment of medial frontal regions suggests compensation via an upregulation mechanism. This upregulation might contribute to maintaining efficient cognitive functioning when posterior cortical function is progressively reduced
The 36-Item Yoni Task: Normative Data for the Clinical Assessment of Theory of Mind
No full textBackground: The evaluation of Theory of Mind (ToM) in the clinical setting remains limited due to the lack of valid instruments for a quick and reliable assessment. In this study, the psychometric properties of the Yoni-36 task were tested, and correction grids, equivalence scores, and normative data were computed. Methods: In total, 318 healthy subjects (169 females; mean age = 42.22 ± 18.11 years; mean education = 15.01 ± 3.43 years) were enrolled and administered the Yoni-36 task. Results: Statistical analysis showed good-to-high internal consistency, split-half reliability, and discrimination ability (especially for the second-order items) of the Yoni-36 task. Regression models highlighted the predictive role of age and education on second-order, affective, cognitive accuracy, and response time scores. Education influenced the first-order ToM response time score as well. Based on β values of the regressions, raw scores of the Yoni task were adjusted for sex, age, and education, and correction grids were computed. The equivalent scores indicated an accuracy index score < 0.69 and a response time index score < 0.83 as cut-off points for ToM competence. Normative data reported a mean accuracy and response time index score of 0.90 ± 0.11 and 0.91 ± 0.05 in the Italian population, respectively. Conclusions: The Yoni-36 proved to be a valid instrument for a quick and reliable ToM assessment, suitable to be included in neuropsychological batteries and to be used in routine clinical practice
Impact of Anatomical Variability on Sensitivity Profile in fNIRS–MRI Integration
Full text linkFunctional near-infrared spectroscopy (fNIRS) is an important non-invasive technique used to monitor cortical activity. However, a varying sensitivity of surface channels vs. cortical structures may suggest integrating the fNIRS with the subject-specific anatomy (SSA) obtained from routine MRI. Actual processing tools permit the computation of the SSA forward problem (i.e., cortex to channel sensitivity) and next, a regularized solution of the inverse problem to map the fNIRS signals onto the cortex. The focus of this study is on the analysis of the forward problem to quantify the effect of inter-subject variability. Thirteen young adults (six males, seven females, age 29.3 ± 4.3) underwent both an MRI scan and a motor grasping task with a continuous wave fNIRS system of 102 measurement channels with optodes placed according to a 10/5 system. The fNIRS sensitivity profile was estimated using Monte Carlo simulations on each SSA and on three major atlases (i.e., Colin27, ICBM152 and FSAverage) for comparison. In each SSA, the average sensitivity curves were obtained by aligning the 102 channels and segmenting them by depth quartiles. The first quartile (depth < 11.8 (0.7) mm, median (IQR)) covered 0.391 (0.087)% of the total sensitivity profile, while the second one (depth < 13.6 (0.7) mm) covered 0.292 (0.009)%, hence indicating that about 70% of the signal was from the gyri. The sensitivity bell-shape was broad in the source–detector direction (20.953 (5.379) mm FWHM, first depth quartile) and steeper in the transversal one (6.082 (2.086) mm). The sensitivity of channels vs. different cortical areas based on SSA were analyzed finding high dispersions among subjects and large differences with atlas-based evaluations. Moreover, the inverse cortical mapping for the grasping task showed differences between SSA and atlas based solutions. In conclusion, integration with MRI SSA can significantly improve fNIRS interpretation
Correlation of Brain Structural and Functional Connectivity Indexes
No full textResting state functional magnetic resonance imaging (rsfMRI) and tractography, derived from diffusion weighted imaging (DWI), are well-established neuroimaging techniques to investigate respectively brain functional connectivity (FC) and structural connectivity (SC) (van den Heuvel et al., 2009). The aim of this work was exploring the correlation between FC and SC within the default mode network (DMN), the left lateral network (LLN) and the right lateral network (RLN). In a sample of 19 healthy subjects, the RSNs were extracted at group level through the spatial independent component analysis (ICA), according to Dipasquale et al. (2015). DMN, LLN and RLN were selected and then divided into their spatial nodes, defined as anatomically separated clusters. For each subject, FC strength was calculated as the Pearson correlation coefficient (transformed in Z-score) between the pairs of rsfMRI signal time courses associated to the pairs of the RSN nodes. Averaging these values across subjects, group FC indexes were obtained. The same pairs of clusters were also used as seed and target regions in single subject probabilistic tractography. For each reconstructed tract the number of voxels above-threshold (15%) (Khalsa et al., 2014) was adopted as SC index. Averaging these values across subjects, the group SC indexes were obtained for each RSN. Finally, FC and SC indexes were correlated by Pearson correlation coefficient. As a result, we observed a positive FC-SC correlation in LLN (statistically significant, p<0.05) and in RLN. Regarding the DMN, no significant FC-SC correlation was found, even though it revealed high values of FC and SC separately. Our results suggest that combining FC and SC indexes allows to evaluate if a high communication level within RSNs is determined by direct white matter fiber pathways or rather by collateral circuits not detectable with the available tractographic techniques
Analysis of resting state sub-networks from high-dimensional ICA: disconnections in Alzheimer's disease
No full textAbnormal cortical and thalamic development in children with Borderline Intellectual Functioning
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