Cognitive reserve (CR) prevents cognitive decline and delays neurodegeneration. Recent epidemiological evidence suggests that lifelong bilingualism may act as CR delaying the onset of dementia by ...∼4.5 y. Much controversy surrounds the issue of bilingualism and its putative neuroprotective effects. We studied brain metabolism, a direct index of synaptic function and density, and neural connectivity to shed light on the effects of bilingualism in vivo in Alzheimer’s dementia (AD). Eighty-five patients with probable AD and matched for disease duration (45 German-Italian bilingual speakers and 40 monolingual speakers) were included. Notably, bilingual individuals were on average 5 y older than their monolingual peers. In agreement with our predictions and with models of CR, cerebral hypometabolism was more severe in the group of bilingual individuals with AD. The metabolic connectivity analyses crucially supported the neuroprotective effect of bilingualism by showing an increased connectivity in the executive control and the default mode networks in the bilingual, compared with the monolingual, AD patients. Furthermore, the degree of lifelong bilingualism (i.e., high, moderate, or low use) was significantly correlated to functional modulations in crucial neural networks, suggesting both neural reserve and compensatory mechanisms. These findings indicate that lifelong bilingualism acts as a powerful CR proxy in dementia and exerts neuroprotective effects against neurodegeneration. Delaying the onset of dementia is a top priority of modern societies, and the present in vivo neurobiological evidence should stimulate social programs and interventions to support bilingual or multilingual education and the maintenance of the second language among senior citizens.
Liquid-phase-pressureless-sintered SiC–AlN–Y
2O
3 composites were coated by means of modified pack cementation process (OXPAC, OXidation-assisted-PAck Cementation) using rare-earth oxides, RE
2O
3 ...(RE
=
Sc, Er, Sm, Lu, Ho), as reactive powders. The coatings, composed by the oxidation products of SiC, AlN and rare-earth silicates, were adherent to the substrate, without porosity and with a thickness of 10
μm. The oxidation resistance of the coated SiC–AlN–Y
2O
3 ceramics was also investigated at 1500
°C for a period of 200
h. The coated samples showed specific weight gain lower than the uncoated and pre-oxidised samples. Furthermore, the specific weight gain linearly increased with the rare-earth cationic radius.
To investigate functional brain network architecture in early-onset Alzheimer disease (EOAD) and behavioral variant frontotemporal dementia (bvFTD).
Thirty-eight patients with bvFTD, 37 patients with ...EOAD, and 32 age-matched healthy controls underwent 3D T1-weighted and resting-state fMRI. Graph analysis and connectomics assessed global and local functional topologic network properties, regional functional connectivity, and intrahemispheric and interhemispheric between-lobe connectivity.
Despite similarly extensive cognitive impairment relative to controls, patients with EOAD showed severe global functional network alterations (lower mean nodal strength, local efficiency, clustering coefficient, and longer path length), while patients with bvFTD showed relatively preserved global functional brain architecture. Patients with bvFTD demonstrated reduced nodal strength in the frontoinsular lobe and a relatively focal altered functional connectivity of frontoinsular and temporal regions. Functional connectivity breakdown in the posterior brain nodes, particularly in the parietal lobe, differentiated patients with EOAD from those with bvFTD. While EOAD was associated with widespread loss of both intrahemispheric and interhemispheric functional correlations, bvFTD showed a preferential disruption of the intrahemispheric connectivity.
Disease-specific patterns of functional network topology and connectivity alterations were observed in patients with EOAD and bvFTD. Graph analysis and connectomics may aid clinical diagnosis and help elucidate pathophysiologic differences between neurodegenerative dementias.
The Two-step sintering (TSS) method was applied to the pressureless sintering of commercial silicon carbide powder doped with boron and carbon. The microstructural and mechanical properties of ...TSS-SiC were compared to those of sintered SiC obtained with the conventional thermal cycle (CS-SiC). TSS-SiC was densified (97.7% T.D.) at 2050°C instead of 2200°C needed for CS-SiC (97% T.D.). Furthermore, TSS-SiC showed finer microstructure and enhanced mechanical properties. In particular, flexural strength of the TSS-SiC materials greatly increased up to 556MPa, much higher than 341MPa reached by CS-SiC.
Background and aims:
To describe the clinical and neuropsychological features of a large group of cognitively intact persons subjected to brain high-resolution magnetic resonance (MR), to compare ...them with the general population, and to set norms for medial temporal atrophy and white matter lesions.
Methods:
Participants in the Italian Brain Normative Archive (IBNA) study were 483 consecutive volunteers undergoing MR for reasons unrelated to cognition (migraine or headache, visual and balance or auditory disturbances, paresthesias, and others) and showing no brain damage. Manual tracing of hippocampal and amygdalar volumes and visual rating of white matter lesions were made. The whole study group was stratified by age (≤60 and 60+ yrs) and by the reason for MR prescription.
Results:
In the whole group, mean age and education were 52.4±13.7 and 9.8±4.2 years, respectively, and the prevalence of women was 63%. Clinical, neuropsychological and morphometric features were similar in the stratified subgroups. Neuropsychological features were those expected for age and education based on Italian normative values. Hippocampal and amygdalar volumes were not associated with age, except for the right amygdala (B −0.159, 95% CI −0.28 to −0.03, p=0.016).
Conclusions:
Persons in the IBNA study had clinical and neuropsychological features consistent with that of the general population. Their brain morphometric features may be used as normative references for patients with suspected neurodegenerative disorders.
Alzheimer's disease (AD) and frontotemporal dementia (FTD) are leading causes of cognitive decline. Optical coherence tomography (OCT) allows the measurement of thickness of retinal neuroaxonal ...layers. While in AD and mild cognitive impairment (MCI), retinal nerve fiber layer (RNFL) thinning is frequently reported, less information is available on ganglion cell layer-inner plexiform layer (GCL-IPL). Data on FTD are lacking.
To obtain cross-sectional information on RNFL and GCL-IPL thickness among MCI, AD, FTD, and healthy controls (HC), and their correlations with dementia severity.
Peripapillary OCT scans were obtained in 27 MCI, 39 AD, 17 FTD, 49 HC using high-definition Heidelberg Spectral-domain OCT, with RNFL and GCL-IPL thickness measurement. Statistical analysis tested group effects and correlation with gender, disease duration and severity (Mini-Mental State Examination, MMSE).
RNFL showed a significant group effect F(4,132) = 3.786, p = 0.006, being reduced versus controls in MCI (p = 0.033), moderate AD (p = 0.025), and FTD (p < 0.001), and versus mild AD in FTD (p = 0.042). GCL-IPL showed a significant group effect as well F(4,121) = 5.104, p < 0.001, with reduction in moderate AD versus HC (p < 0.001), MCI (p = 0.037), and mild AD (p = 0.009); in FTD versus HC (p = 0.002) and mild AD (p = 0.038). In AD, GCL-IPL correlated with MMSE (r = 0.487, p = 0.003), without significant effects of age, gender, or disease duration.
Retinal neuroaxonal thinning occurs in MCI/AD consistently with previous reports, as well as in FTD. Correlation with disease severity in AD suggests that retinal and brain neurodegeneration may occur in parallel to some extent, and prompts larger studies aimed at providing surrogate endpoints for clinical trials in AD.
Dementia with Lewy Bodies (DLB) is characterized by a prominent deficit in visuospatial abilities. Visuospatial impairment is also detectable in the course of Alzheimer's dementia (AD). However, ...visuospatial impairment presents some differences in these two conditions, suggesting pathological involvement of distinct brain circuits. Recent studies applied a new method to score the Mini Mental State Examination (MMSE) pentagon copy subtest, namely the Qualitative Scoring Pentagon Test (QSPT), which is a sensitive measure of visuospatial abilities. Using 18Ffluorodeoxy-glucose positron emission tomography (FDG-PET), we assessed the relationship between in vivo brain metabolic dysfunction and visuospatial deficits, in terms of QSPT total value, in DLB and AD.
Sixty Patients were diagnosed as DLB (n = 35) and AD (n = 25) dementia according with the standard research diagnostic criteria. Each patient underwent a FDG-PET scan as support for the final diagnosis. Patients underwent an extended neuropsychological evaluation, including MMSE, language, memory, executive functions and visuospatial abilities tests. The MMSE QSPT scoring was calculated following the methods by Caffarra et al. (2013). Offline voxel-wise correlation analysis between QSPT total scores and FDG-PET brain metabolism was then performed, correcting for MMSE, sex and disease duration.
Both groups presented reduced visuospatial performances, as assessed by QSPT scores. DLB compared to AD showed a statistically significant difference in QSPT rotation parameter (p = 0.022). In DLB, worse performance at QSPT total score, i.e. more severe visuospatial impairment, correlated with brain occipital hypometabolism (i.e. lateral occipital cortex, calcarine cortex, fusiform and lingual gyri). In AD, worse performance at QSPT total score correlated with brain hypometabolism in the right parietal cortex (i.e. superior and inferior parietal cortex and angular gyrus).
These findings reveal that visuospatial deficits may derive from distinct brain alterations in AD and DLB. We propose that the inabilities to perform correctly the QSPT task is related to altered visuoperceptual process in DLB, and visuospatial process in AD. This is consistent with our results showing hypometabolism in brain system related to visuoperceptual processing, namely the occipital cortex in DLB, and visuospatial processing, namely parietal cortex in AD.
•Qualitative Scoring Pentagon Test is useful for visuospatial deficits assessment.•Visuospatial deficits commonly occur in both Lewy body and Alzheimer's dementia.•Visuospatial deficits correlate with occipital hypometabolism in Lewy body dementia.•Visuospatial deficits correlate with parietal hypometabolism in Alzheimer's dementia.•Different neurocircuits underlie visuospatial deficits in the two conditions.
In order to improve the oxidation resistance of Cf/Cs produced by chemical vapour infiltration, a multilayer coating based on silicon carbide and molybdenum disilicide was produced by two-step pack ...cementation technique. The inner SiC layer with a thickness up to 25 μm was obtained without promoted reaction additives by varying the composition, and thermal treatment conditions. The SiC/SiC-MoSi2 coating was produced with a thickness up to 80 μm by two step pack cementation, considering the effect of the inner layer characteristic. The enhancement of the oxidation resistance, observed in SiC/SiC-MoSi2 coated Cf/Cs by means of thermal analysis in flowing air up to 1500 °C, was due to the formation of SiO2 promoted by the passive oxidation of silicon carbide and molybdenum disilicide.
Abstract Using resting-state functional magnetic resonance imaging and graph analysis, the topological organization of the functional brain network connectivity was explored in patients with ...left-sided onset semantic variant (SV) of primary progressive aphasia relative to healthy controls. Functional brain networks in SV patients were characterized by a significantly lower mean network degree, clustering coefficient, and global efficiency, longer characteristic path length and higher assortativity compared with controls. SV patients showed also a strongly left-lateralized loss of hubs, and reduced nodal degree in the inferior and ventral temporal regions and occipital cortices. In SV, the decreased nodal degree extended into the medial and ventral frontal cortex bilaterally, left amygdala and/or hippocampus, and left caudate nucleus. These findings provide evidence that the focal structural degeneration of the inferior temporal, and perysilvian language regions in SV patients ultimately results in a distributed pattern of functional connectivity abnormalities. The local network analysis shows that SV is associated with a functional degradation in the “pan-modal” inferior and/or ventral temporal regions, and the “modality-specific” visual cortical origin of the ventral processing pathway.
The 3 clinical presentations of primary progressive aphasia (PPA) reflect heterogenous neuropathology, which is difficult to be recognized in vivo. Resting-state (RS) EEG is promising for the ...investigation of brain electrical substrates in neurodegenerative conditions. In this study, we aim to explore EEG cortical sources in the characterization of the 3 variants of PPA.
This is a cross-sectional, single-center, memory center-based cohort study. Patients with PPA and healthy controls were consecutively recruited at the Neurology Unit, IRCCS San Raffaele Scientific Institute (Milan, Italy). Each participant underwent an RS 19-channel EEG. Using standardized low-resolution brain electromagnetic tomography, EEG current source densities were estimated at voxel level and compared among study groups. Using an RS functional MRI-driven model of source reconstruction, linear lagged connectivity (LLC) values within language and extra-language brain networks were obtained and analyzed among groups.
Eighteen patients with logopenic PPA variant (lvPPA; mean age = 72.7 ± 6.6; % female = 52.4), 21 patients with nonfluent/agrammatic PPA variant (nfvPPA; mean age = 71.7 ± 8.1; % female = 66.6), and 9 patients with semantic PPA variant (svPPA; mean age = 65.0 ± 6.9; % female = 44.4) were enrolled in the study, together with 21 matched healthy controls (mean age = 69.2 ± 6.5; % female = 57.1). Patients with lvPPA showed a higher delta density than healthy controls (
< 0.01) and patients with nfvPPA (
< 0.05) and svPPA (
< 0.05). Patients with lvPPA also displayed a greater theta density over the left posterior hemisphere (
< 0.01) and lower alpha2 values (
< 0.05) over the left frontotemporal regions than controls. Patients with nfvPPA showed a diffuse greater theta density than controls (
< 0.05). LLC was altered in all patients relative to controls (
< 0.05); the alteration was greater at slow frequency bands and within language networks than extra-language networks. Patients with lvPPA also showed greater LLC values at theta band than patients with nfvPPA (
< 0.05).
EEG findings in patients with PPA suggest that lvPPA-related pathology is associated with a characteristic disruption of the cortical electrical activity, which might help in the differential diagnosis from svPPA and nfvPPA. EEG connectivity was disrupted in all PPA variants, with distinct findings in disease-specific PPA groups.
This study provides Class IV evidence that EEG analysis can distinguish PPA due to probable Alzheimer disease from PPA due to probable FTD from normal aging.
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