Tecniche Elettrotomografiche per la caratterizzazione dei tessuti biologici

Electrical impedance tomography (EIT) is an imaging modality wherein the spatial map of conductivity and permittivity inside a medium is obtained from a set of surface electrical measurements. Electrodes are brought into contact with the surface of the object being imaged and a set of currents are applied and the corresponding voltages are measured. These voltages and currents are then used to estimate the electrical properties of the object using an image reconstruction algorithm which relies on an accurate model of the electrical interaction. The process of property estimation, called inverse problem, is highly ill-posed and it requires a Regularization method. The objective of this Thesis was to develop a device for imaging using the EIT technique, which was convenient, noninvasive, easily programmable, portable and relatively cheap in contrast to many other diagnostic tool. In this direction a simple EIT system and its hardware and software parts are developed. The data processing was accomplished by utilizing the EIDORS toolkit, which was developed for application to this nonlinear and ill-posed inverse problem. Experiments have indicated that the EIT system can reconstruct resistive and capacitive images of good contrast despite errors in the measurement are not taken in account

Strategic lesions in the anterior thalamic radiation and apathy in early Alzheimer's disease

BACKGROUND Behavioural disorders and psychological symptoms of Dementia (BPSD) are commonly observed in Alzheimer's disease (AD), and strongly contribute to increasing patients' disability. Using voxel-lesion-symptom mapping (VLSM), we investigated the impact of white matter lesions (WMLs) on the severity of BPSD in patients with amnestic mild cognitive impairment (a-MCI). METHODS Thirty-one a-MCI patients (with a conversion rate to AD of 32% at 2 year follow-up) and 26 healthy controls underwent magnetic resonance imaging (MRI) examination at 3T, including T2-weighted and fluid-attenuated-inversion-recovery images, and T1-weighted volumes. In the patient group, BPSD was assessed using the Neuropsychiatric Inventory-12. After quantitative definition of WMLs, their distribution was investigated, without an a priori anatomical hypothesis, against patients' behavioural symptoms. Unbiased regional grey matter volumetrics was also used to assess the contribution of grey matter atrophy to BPSD. RESULTS Apathy, irritability, depression/dysphoria, anxiety and agitation were shown to be the most common symptoms in the patient sample. Despite a more widespread anatomical distribution, a-MCI patients did not differ from controls in WML volumes. VLSM revealed a strict association between the presence of lesions in the anterior thalamic radiations (ATRs) and the severity of apathy. Regional grey matter atrophy did not account for any BPSD. CONCLUSIONS This study indicates that damage to the ATRs is strategic for the occurrence of apathy in patients with a-MCI. Disconnection between the prefrontal cortex and the mediodorsal and anterior thalamic nuclei might represent the pathophysiological substrate for apathy, which is one of the most common psychopathological symptoms observed in dementia

Walking, Running, Swimming: An Analysis of the Effects of Land and Water Aerobic Exercises on Cognitive Functions and Neural Substrat

In the brain and cognitive reserves framework, aerobic exercise is considered as a protective lifestyle factor able to induce positive effects on both brain structure and function. However, specific aspects of such a beneficial effect still need to be completely clarified. To this aim, the present narrative review focused on the potential brain/cognitive/neural reserve–construction mechanisms triggered by different aerobic exercise types (land activities; such as walking or running; vs. water activities; such as swimming), by considering human and animal studies on healthy subjects over the entire lifespan. The literature search was conducted in PubMed database. The studies analyzed here indicated that all the considered kinds of activities exert a beneficial effect on cognitive/behavioral functions and on the underlying brain neurobiological processes. In particular, the main effects observed involve the cognitive domains of memory and executive functions. These effects appear related to structural and functional changes mainly involving the fronto-hippocampal axis. The present review supports the requirement of further studies that investigate more specifically and systematically the effects of each type of aerobic activity, as a basis to plan more effective and personalized interventions on individuals as well as prevention and healthy promotion policies for the general population

The beneficial effects of physical exercise on visuospatial working memory in preadolescent children

The relationship between physical exercise and improvement in specific cognitive domains in children and adolescents who play sport has been recently reported, although the effects on visuospatial abilities have not yet been well explored. This study is aimed at evaluating in school-age children practicing artistic gymnastics the visuospatial memory by using a table version of the Radial Arm Maze (table-RAM) and comparing their performances with those ones who do not play any sport. The visuospatial performances of 14 preadolescent girls practicing artistic gymnastics aged between 7 and 10 years and those of 14 preadolescent girls not playing any sport were evaluated in the table-RAM forced-choice paradigm that allows disentangling short-term memory from working memory abilities. Data showed that the gymnasts obtained better performances than control group mainly in the parameters evaluating working memory abilities, such as within-phase errors and spatial span. Our findings emphasizing the role of physical activity on cognitive performances impel to promote physical exercise in educational and recreational contexts as well as to analyse the impact of other sports besides gymnastics on cognitive functioning

How the cognitive reserve interacts with β-amyloid deposition in mitigating FDG metabolism: An observational study

This observational study had the aim to assess the interaction between cognitive reserve (CR) and cerebrospinal fluid β-amyloid1-42 (Aβ1-42) in modulating brain [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) metabolism in patients with moderate Alzheimer disease (AD).Twenty-seven patients with probable AD and 25 neurological normal subjects (NNS) entered the study. All participants had an FDG-PET scan, and AD patients also received a lumbar puncture to measure Aβ1-42, 181p-tau, and Tau concentrations. Based on years of formal education, AD patients were classified as highly educated-AD (years of formal education >5) or less educated-AD (years of formal education <5). By using a voxel-wise approach, we first investigated differences in the cerebral glucose uptake between AD and NNS, then we assessed the interaction between level of education (a proxy of CR) and cerebrospinal fluid biomarkers on FDG-PET metabolism in the patient groups.Significantly lower glucose uptake was observed in the posterior cingulate gyrus, in the precuneus, in the inferior and medial temporal gyrus, and in the inferior parietal lobule of AD patients compared with NNS. A significant interaction was found between CR and Aβ1-42 values on brain metabolism in the inferior and medial temporal gyrus bilaterally.The AD patients with higher CR level and marked signs of neuropathology showed glucose hypometabolism in regions typically targeted by AD pathology. This finding supports the hypothesis that CR partially compensates for the effect of Aβ plaques on cognitive impairment, helps in patients' clinical staging, and opens new possibilities for the development of nonpharmacological interventions

Cerebellar white matter disruption in Alzheimer’s Disease patients: a Diffusion Tensor Imaging study

The cognitive role of the cerebellum has recently gained much attention, and its pivotal role in Alzheimer’s disease (AD) has now been widely recognized. Diffusion tensor imaging (DTI) has been used to evaluate the disruption of the microstructural milieu in AD, and though several white matter (WM) tracts such as corpus callosum, inferior and superior longitudinal fasciculus, cingulum, fornix, and uncinate fasciculus have been evaluated in AD, data on cerebellar WM tracts are currently lacking. We performed a tractography-based DTI reconstruction of the middle cerebellar peduncle (MCP), and the left and right superior cerebellar peduncles separately (SCPL and SCPR) and addressed the differences in fractional anisotropy (FA), axial diffusivity (Dax), radial diffusivity (RD), and mean diffusivity (MD) in the three tracts between 50 patients with AD and 25 healthy subjects. We found that AD patients showed a lower FA and a higher RD compared to healthy subjects in MCP, SCPL, and SCPR. Moreover, a higher MD was found in SCPR and SCPL and a higher Dax in SCPL. This result is important as it challenges the traditional view that WM bundles in the cerebellum are unaffected in AD and might identify new targets for therapeutic interventions

In vivo mapping of brainstem nuclei functional connectivity disruption in Alzheimer's disease

We assessed here functional connectivity changes in the locus coeruleus (LC) and ventral tegmental area (VTA) of patients with Alzheimer's disease (AD). We recruited 169 patients with either AD or amnestic mild cognitive impairment due to AD and 37 elderly controls who underwent cognitive and neuropsychiatric assessments and resting-state functional magnetic resonance imaging at 3T. Connectivity was assessed between LC and VTA and the rest of the brain. In amnestic mild cognitive impairment patients, VTA disconnection was predominant with parietal regions, while in AD patients, it involved the posterior nodes of the default-mode network. We also looked at the association between neuropsychiatric symptoms (assessed by the neuropsychiatric inventory) and VTA connectivity. Symptoms such as agitation, irritability, and disinhibition were associated with VTA connectivity with the parahippocampal gyrus and cerebellar vermis, while sleep and eating disorders were associated with VTA connectivity to the striatum and the insular cortex. This suggests a contribution of VTA degeneration to AD pathophysiology and to the occurrence of neuropsychiatric symptoms. We did not find evidence of LC disconnection, but this could be explained by the size of this nucleus, which makes it difficult to isolate. These results are consistent with animal findings and have potential implications for AD prognosis and therapies

Motor and Linguistic Linking of Space and Time in the Cerebellum

Background: Recent literature documented the presence of spatial-temporal interactions in the human brain. The aim of the present study was to verify whether representation of past and future is also mapped onto spatial representations and whether the cerebellum may be a neural substrate for linking space and time in the linguistic domain. We asked whether processing of the tense of a verb is influenced by the space where response takes place and by the semantics of the verb. Principal Findings: Responses to past tense were facilitated in the left space while responses to future tense were facilitated in the right space. Repetitive transcranial magnetic stimulation (rTMS) of the right cerebellum selectively slowed down responses to future tense of action verbs; rTMS of both cerebellar hemispheres decreased accuracy of responses to past tense in the left space and to future tense in the right space for non-verbs, and to future tense in the right space for state verbs. Conclusions: The results suggest that representation of past and future is mapped onto spatial formats and that motor action could represent the link between spatial and temporal dimensions. Right cerebellar, left motor brain networks could be part of the prospective brain, whose primary function is to use past experiences to anticipate future events. Bot

Brain connectomics' modification to clarify motor and nonmotor features of myotonic dystrophy type 1

The adult form of myotonic dystrophy type 1 (DM1) presents with paradoxical inconsistencies between severity of brain damage, relative preservation of cognition, and failure in everyday life. This study, based on the assessment of brain connectivity and mechanisms of plasticity, aimed at reconciling these conflicting issues. Resting-state functional MRI and graph theoretical methods of analysis were used to assess brain topological features in a large cohort of patients with DM1. Patients, compared to controls, revealed reduced connectivity in a large frontoparietal network that correlated with their isolated impairment in visuospatial reasoning. Despite a global preservation of the topological properties, peculiar patterns of frontal disconnection and increased parietal-cerebellar connectivity were also identified in patients' brains. The balance between loss of connectivity and compensatory mechanisms in different brain networks might explain the paradoxical mismatch between structural brain damage and minimal cognitive deficits observed in these patients. This study provides a comprehensive assessment of brain abnormalities that fit well with both motor and nonmotor clinical features experienced by patients in their everyday life. The current findings suggest that measures of functional connectivity may offer the possibility of characterizing individual patients with the potential to become a clinical tool

Multicenter prospective study on the prevalence of colistin resistance in escherichia coli: Relevance of mcr-1-positive clinical isolates in Lombardy, Northern Italy

Background: The emergence of the plasmid-mediated colistin resistance mechanism in Escherichia coli has raised concern among public health experts as colistin is a last-line antimicrobial resort. The primary aim of the study was to investigate the prevalence of this resistance trait in E. coli isolates circulating in the Lombardy region, Northern Italy. The presence of mcr-type genes and their genetic relationship were also studied. Materials and methods: A prospective study was performed during a 4-month period (May to August, 2016) in six acute care Hospitals. Consecutive nonduplicate clinical isolates of E. coli from any type of clinical specimen, with the exception of rectal swabs, were included in the study. Isolates that exhibited MIC values for colistin &gt;2 mg/L were further investigated. Bacterial identification was obtained by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Amplification of mcr-type genes (-1 to -5 variants) and microarray analysis were accomplished. Repetitive sequence-based PCR (Rep-PCR) and multilocus sequence typing (MLST) analysis were used for genotyping. Results: Overall, 3,902 consecutive E. coli isolates (2,342 from outpatients, 1,560 from inpatients) were evaluated during the study period. Of them, 18/3,902 (0.5%), collected from 4/6 centers, showed resistance to colistin. These isolates were mostly obtained from urine of both outpatients (n=12) and inpatients (n=6). Colistin MIC values ranged from 4 to 8 mg/L. The mcr-1 gene was detected in 10/18 isolates (7 from outpatients, 3 from inpatients). Rep-PCR and MLST analysis revealed the presence of nine different clusters. Further mcr-type genes were not detected. Conclusion: Resistance to colistin in E. coli clinical isolates appears low in our geographic area. With regard to mcr-1-positive isolates, they accounted for approximately 50% of colistin-resistant E. coli isolates, thus representing a relevant resistance mechanism in this context. Although overall limited, the presence of mcr-1 determinant in our region should not be ignored and great concern should be given to the continuous surveillance