Selective imitation impairments differentially interact with language processing

Whether motor and linguistic representations of actions share common neural structures has recently been the focus of an animated debate in cognitive neuroscience. Group studies with brain-damaged patients reported association patterns of praxic and linguistic deficits whereas single case studies documented double dissociations between the correct execution of gestures and their comprehension in verbal contexts. When the relationship between language and imitation was investigated, each ability was analysed as a unique process without distinguishing between possible subprocesses. However, recent cognitive models can be successfully used to account for these inconsistencies in the extant literature. In the present study, in 57 patients with left brain damage, we tested whether a deficit at imitating either meaningful or meaningless gestures differentially impinges on three distinct linguistic abilities (comprehension, naming and repetition). Based on the dual-pathway models, we predicted that praxic and linguistic performance would be associated when meaningful gestures are processed, and would dissociate for meaningless gestures. We used partial correlations to assess the association between patients' scores while accounting for potential confounding effects of aspecific factors such age, education and lesion size. We found that imitation of meaningful gestures significantly correlated with patients' performance on naming and repetition (but not on comprehension). This was not the case for the imitation of meaningless gestures. Moreover, voxel-based lesion-symptom mapping analysis revealed that damage to the angular gyrus specifically affected imitation of meaningless gestures, independent of patients' performance on linguistic tests. Instead, damage to the supramarginal gyrus affected not only imitation of meaningful gestures, but also patients' performance on naming and repetition. Our findings clarify the apparent conflict between associations and dissociations patterns previously observed in neuropsychological studies, and suggest that motor experience and language can interact when the two domains conceptually overla

Cerebral hypoperfusion in post-COVID-19 cognitively impaired subjects revealed by arterial spin labeling MRI

Cognitive impairment is one of the most prevalent symptoms of post Severe Acute Respiratory Syndrome COronaVirus 2 (SARS-CoV-2) state, which is known as Long COVID. Advanced neuroimaging techniques may contribute to a better understanding of the pathophysiological brain changes and the underlying mechanisms in post-COVID-19 subjects. We aimed at investigating regional cerebral perfusion alterations in post-COVID-19 subjects who reported a subjective cognitive impairment after a mild SARS-CoV-2 infection, using a non-invasive Arterial Spin Labeling (ASL) MRI technique and analysis. Using MRI-ASL image processing, we investigated the brain perfusion alterations in 24 patients (53.0 ± 14.5 years, 15F/9M) with persistent cognitive complaints in the post COVID-19 period. Voxelwise and region-of-interest analyses were performed to identify statistically significant differences in cerebral blood flow (CBF) maps between post-COVID-19 patients, and age and sex matched healthy controls (54.8 ± 9.1 years, 13F/9M). The results showed a significant hypoperfusion in a widespread cerebral network in the post-COVID-19 group, predominantly affecting the frontal cortex, as well as the parietal and temporal cortex, as identified by a non-parametric permutation testing (p < 0.05, FWE-corrected with TFCE). The hypoperfusion areas identified in the right hemisphere regions were more extensive. These findings support the hypothesis of a large network dysfunction in post-COVID subjects with cognitive complaints. The non-invasive nature of the ASL-MRI method may play an important role in the monitoring and prognosis of post-COVID-19 subjects

Dependence of the fractional anisotropy in cervical spine from the number of diffusion gradients, repeated acquisition and voxel size

The aim of this study is to investigate the consequences of using different gradient schemes, number of repeated measurements and voxel size on the fractional anisotropy (FA) value in a diffusion tensor imaging (DTI) sequence on the cervical tract of the spinal cord. Twenty healthy volunteers underwent a total of 86 DTI axial acquisitions performed by using different voxel size and number of diffusion gradient directions (NDGDs). Three different diffusion gradient schemes were applied, named 6, 15 and 32 according to the NDGD. Furthermore, some acquisitions were repeated to investigate the effects of image averaging on FA value. Our results indicate that the FA value in the cervical spinal cord decreases when increasing the NDGD for a fixed spatial resolution, or when identical acquisitions are repeated, thus, increasing the acquisition time. This effect is observed in all subjects without exceptions, and the differences result statistically significant: the average FA obtained from 6, 15 and 32 NDGD is 0.84 (range, 0.82-0.87), 0.75 (range, 0.68-0.80) and 0.70 (range, 0.65-0.77), respectively, for isotropic 8 mm3 voxel size. When varying the spatial resolution in a volume range of 2 to 8 mm3 for a fixed NDGD (6 or 15), the differences in FA values are smaller albeit still statistically significant: the smaller the voxel, the larger the FA. No significant dependence of the FA value from the spatial resolution is observed in the 32 NDGD acquisitions in the studied volume range. In conclusion, our results indicate that the value of the FA in the cervical tract of the spinal cord vary with regularity in intrasubject acquisitions when modifying the NDGD and when repeated acquisitions are used; these observations confirm that the signal-to-noise ratio introduces a systematic error in FA measurements that does not allow simple comparison of quantitative results obtained from separated studies. © 2010 Elsevier Inc. All rights reserved

Neuropsychological evidence for a strategic control of multiple routes in imitation. Brain. 130, 1111– 1126. doi: 10.1093/brain/awm003

Previous studies have suggested that imitators can reproduce known gestures shown by a model using a semantic, indirect route, and novel gestures using a sublexical, direct route. In the present study we aimed at testing the validity of such a dual-route model of action imitation. Patients with either left-brain damage (LBD) or right-brain damage (RBD) were tested on an action imitation task. Actions were either meaningful (n ¼ 20) or meaningless (n ¼ 20), and were presented in an intermingled list and, on a different day, in separate lists. We predicted that, in the mixed condition, patients would use a direct route to imitate meaningful and meaningless actions, as it allows the imitation of both action types. In the blocked condition, patients were expected to select the semantic route for meaningful actions and the direct route for meaningless actions. As hypothesized, none of the 32 patients showed dissociations between imitation of meaningful and meaningless actions in the mixed presentation. In contrast, eight patients showed a dissociation between imitation of meaningful actions and imitation of meaningless actions in the blocked presentation. Moreover, two of these patients showed a classical double dissociation between the imitation of the two action types. Results were interpreted in support of the validity of a dual-route model for explaining action imitation. We argue that the decrease in imitation of meaningful actions, relative to meaningless actions, is caused by a damage of the semantic route, and that the decline in imitation of meaningless actions, relative to meaningful actions, is produced by a breakdown of the direct route. The brain areas that were lesioned in all six LBD patients who showed a dissociation were in the superior temporal gyrus and the angular gyrus, whereas the two RBD subjects had common lesions of the pallidum and of the putamen. The brain structures affected in our patients with selective apraxia are consistent with those reported before in other neuropsychological reports. They are also in agreement with areas found activated in imaging studies in which the neural mechanisms underlying imitation were examined. Keywords: ideomotor apraxia; inferior parietal cortex; angular gyrus; mirror neurons; hippocampus Abbreviations: BA ¼ Brodmann area; LBD ¼ left-brain damage; PET ¼ positron emission tomography; RBD ¼ right-brain damag

Predictors of mesorectal fascia invasion after gadolinium injection in rectal carcinoma after neoadjuvant therapy

OBJECTIVE: To assess spectral presaturation inversion-recovery MRI sequence with gadolinium to identify predictors of mesorectal fascia (MRF) invasion in patients with locally advanced rectal carcinoma after neoadjuvant therapy. MATERIALS AND METHODS: Sixty-five patients underwent neoadjuvant concomitant radiation and chemotherapy and surgery. Magnetic resonance images were assessed by two radiologists. RESULTS: Linear (odds ratio, 95% confidence intervals: 19.33, 1.98-188.6) and reticular strands (odds ratio, 95% confidence intervals: 9.75, 1.45-67.77) reaching the MRF are predictors of MRF invasion. CONCLUSION: Linear or reticular mesorectal strands reaching the MRF detected at contrast-enhanced MRI represent a predictor of MRF invasion

Arterial enhancing \u2013 only nodules less than 2 cm in diameter in patients with liver cirrhosis: predictors of hepatocellular carcinoma diagnosis on gadobenate dimeglumine - enhanced MR Imaging.

Purpose: To assess whether gadobenate dimeglumine (Gd-BOPTA)-enhanced MR imaging could predict hepatocellular carcinoma (HCC) diagnosis in small arterial enhancing-only nodules detected by contrast-enhanced computed tomography (CT) in patients with liver cirrhosis. Materials and Methods: We prospectively recruited 125 cirrhotic patients (67 males, and 58 females; age: 68 6 12.36 years) with 151 small (<2 cm in diameter) arterial enhancing-only nodules identified by contrast-enhanced CT. All patients were scanned by MR imaging before and after Gd-BOPTA injection during the hepatic arterial phase (HAP), portal venous phase (PVP), equilibrium phase (EP), and hepatobiliary phase (HP). Nodule characterization was based on reference imaging criteria (n \ubc 29 nodules), follow-up (n \ubc 105), or histology (n \ubc 17). Two radiologists (5 and 10 years experience) analyzed the MR images, and logistic regression was conducted to assess how well MR imaging findings could predict HCC diagnosis. Results: Final diagnoses included 115 benign nodules and 36 HCCs. Nodule T2 hyperintensity, T1 hypointensity, PVP-EP hypointensity, and HP hypointensity were the best predictors of HCC on univariate analysis. Nodule T2 hyperintensity, T1 hypointensity, and HP hypointensity, were independent predictors of HCC on multivariate analysis. Conclusion: Gd-BOPTA-enhanced MR imaging provides imaging findings which may predict a diagnosis of HCC in small arterial enhancing-only nodules in cirrhotic patients

Fast T2 mapping of the patellar articular cartilage with gradient and spin-echo magnetic resonance imaging at 1.5 T: validation and initial clinical experience in patients with osteoarthritis

Objective: To evaluate the T2 mapping of patellar articular cartilage in patients with osteoarthritis using gradient and spin-echo (GRASE) magnetic resonance (MR) imaging. Materials and methods After the imaging of a phantom consisting of two sealed 50-ml test objects with different concentrations (30% and 90% weight/volume) of copper sulphate, the T2 mapping of patellar articular cartilage was performed in 35 patients (21 male and 14 female; mean age \ub1 SD 42\ub117 years) with moderate degree of patellar osteoarthritis. Turbo-spin-echo (TSE) (TR milliseconds/ minimum\u2013maximum TE milliseconds 3,000/15\u2013120; total acquisition time 5 min 52 s) and GRASE (TR milliseconds/ minimum\u2013maximum TE milliseconds 3,000/15\u2013120; total acquisition time 1 min 51 s) were employed. In each patient patellar cartilage was segmented at nine locations (three superior, three central, and three inferior) by manually defined regions of interest. T2 relaxation times were calculated using a linear fit applied to the logarithm of signal intensity decay. Results In the phantom the T2 values measured by GRASE were similar to those measured by MR spectroscopy (test object 1: 48.1 ms vs 51 ms; test object 2: 66.8 ms vs 71 ms; P>0.05, Wilcoxon test). In patients GRASE and TSEderived T2 values demonstrated good agreement (mean difference \ub1 SD, 1.81\ub13.63 ms). The within-patient coefficient of variation was 22% for TSE and 23% for GRASE. Conclusion Fast T2 mapping of the patellar articular cartilage can be performed with GRASE within a third of the time of that of standard sequences

Primary malignant melanoma of uterine cervix

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Perfusion CT in acute stroke: Effectiveness of automatically-generated colour maps

OBJECTIVE: To evaluate the accuracy of perfusion CT (pCT) in the definition of the infarcted core and the penumbra, comparing the data obtained from the evaluation of parametric maps [cerebral blood volume (CBV), cerebral blood flow (CBF) and mean transit time (MTT)] with software-generated colour maps. METHODS: A retrospective analysis was performed to identify patients with suspected acute ischaemic strokes and who had undergone unenhanced CT and pCT carried out within 4.5 h from the onset of the symptoms. A qualitative evaluation of the CBV, CBF and MTT maps was performed, followed by an analysis of the colour maps automatically generated by the software. RESULTS: 26 patients were identified, but a direct CT follow-up was performed only on 19 patients after 24-48 h. In the qualitative analysis, 14 patients showed perfusion abnormalities. Specifically, 29 perfusion deficit areas were detected, of which 15 areas suggested the penumbra and the remaining 14 areas suggested the infarct. As for automatically software-generated maps, 12 patients showed perfusion abnormalities. 25 perfusion deficit areas were identified, 15 areas of which suggested the penumbra and the other 10 areas the infarct. The McNemar's test showed no statistically significant difference between the two methods of evaluation in highlighting infarcted areas proved later at CT follow-up. CONCLUSION: We demonstrated how pCT provides good diagnostic accuracy in the identification of acute ischaemic lesions. The limits of identification of the lesions mainly lie at the pons level and in the basal ganglia area. Qualitative analysis has proven to be more efficient in identification of perfusion lesions in comparison with software-generated maps. However, software-generated maps have proven to be very useful in the emergency setting. Advances in knowledge: The use of CT perfusion is requested in increasingly more patients in order to optimize the treatment, thanks also to the technological evolution of CT, which now allows a whole-brain study. The need for performing CT perfusion study also in the emergency setting could represent a problem for physicians who are not used to interpreting the parametric maps (CBV, MTT etc.). The software-generated maps could be of value in these settings, helping the less expert physician in the differentiation between different areas