Genetic Risk for Alzheimer\u27s Disease Alters the Five-Year Trajectory of Semantic Memory Activation in Cognitively Intact Elders

Healthy aging is associated with cognitive declines typically accompanied by increased task-related brain activity in comparison to younger counterparts. The Scaffolding Theory of Aging and Cognition (STAC) (Park and Reuter-Lorenz, 2009; Reuter-Lorenz and Park, 2014) posits that compensatory brain processes are responsible for maintaining normal cognitive performance in older adults, despite accumulation of aging-related neural damage. Cross-sectional studies indicate that cognitively intact elders at genetic risk for Alzheimer\u27s disease (AD) demonstrate patterns of increased brain activity compared to low risk elders, suggesting that compensation represents an early response to AD-associated pathology. Whether this compensatory response persists or declines with the onset of cognitive impairment can only be addressed using a longitudinal design. The current prospective, 5-year longitudinal study examined brain activation in APOE ε4 carriers (N = 24) and non-carriers (N = 21). All participants, ages 65–85 and cognitively intact at study entry, underwent task-activated fMRI, structural MRI, and neuropsychological assessments at baseline, 18, and 57 months. fMRI activation was measured in response to a semantic memory task requiring participants to discriminate famous from non-famous names. Results indicated that the trajectory of change in brain activation while performing this semantic memory task differed between APOE ε4 carriers and non-carriers. The APOE ε4 group exhibited greater activation than the Low Risk group at baseline, but they subsequently showed a progressive decline in activation during the follow-up periods with corresponding emergence of episodic memory loss and hippocampal atrophy. In contrast, the non-carriers demonstrated a gradual increase in activation over the 5-year period. Our results are consistent with the STAC model by demonstrating that compensation varies with the severity of underlying neural damage and can be exhausted with the onset of cognitive symptoms and increased structural brain pathology. Our fMRI results could not be attributed to changes in task performance, group differences in cerebral perfusion, or regional cortical atrophy

Investigating the effect of long-term musical experience on the auditory processing skills of young Maltese adults

Learning and practising a musical instrument has recently been thought to ‘train’ the brain into processing sound in a more refined manner.As a result, musicians experiencing consistent exposure to musical practice have been suspected to have superior auditory processing skills. This study aimed to investigate this phenomenon within the Maltese context, by testing two cohorts of young Maltese adults. Participants in the musician cohort experienced consistent musical training throughout their lifetime, while those in the non-musician cohort did not have a history of musical training. A total of 24 Maltese speakers (14 musicians and 10 non-musicians) of ages ranging between 19 and 31 years were tested for Frequency Discrimination (FD), Duration Discrimination (DD), Temporal Resolution (TR) and speech-in-noise recognition. The main outcomes yielded by each cohort were compared and analysed statistically. In comparison to the non-musician cohort, the musicians performed in a slightly better manner throughout testing. Statistical superiority was surprisingly only present in the FD test. Although musicians displayed a degree of superiority in performance on the other tests, differences in mean scores were not statistically significant. The results yielded by this investigation are to a degree coherent with implications of previous research, in that the effect of long-term musical experience on the trained cohort manifested itself in a slight superiority in performance on auditory processing tasks. However, this difference in scoring was not prominent enough to be statistically significant.peer-reviewe

Large-scale associations between the leukocyte transcriptome and BOLD responses to speech differ in autism early language outcome subtypes.

Heterogeneity in early language development in autism spectrum disorder (ASD) is clinically important and may reflect neurobiologically distinct subtypes. Here, we identified a large-scale association between multiple coordinated blood leukocyte gene coexpression modules and the multivariate functional neuroimaging (fMRI) response to speech. Gene coexpression modules associated with the multivariate fMRI response to speech were different for all pairwise comparisons between typically developing toddlers and toddlers with ASD and poor versus good early language outcome. Associated coexpression modules were enriched in genes that are broadly expressed in the brain and many other tissues. These coexpression modules were also enriched in ASD-associated, prenatal, human-specific, and language-relevant genes. This work highlights distinctive neurobiology in ASD subtypes with different early language outcomes that is present well before such outcomes are known. Associations between neuroimaging measures and gene expression levels in blood leukocytes may offer a unique in vivo window into identifying brain-relevant molecular mechanisms in ASD

Thermal Properties of Commonly Used Clear Aligner Systems As-Received and After Clinical Use

Background/Objectives: The purpose of this study was to investigate the thermal properties, particularly glass transition temperature, of the polymers that are used to fabricate three different types of modern orthodontic aligners. Invisalign, (Align Technology, Inc, Santa Clara, CA, USA), Simpli5 (Allesee Orthodontic Appliances, Sturtevant, WI, USA), and ClearCorrect (ClearCorrect, Round Rock, TX, USA) were examined both as-received and after clinical use to determine if any differences were present both between and within aligners. Materials/Methods: Orthodontic aligners were collected from three different patients using the systems under investigation after two weeks of intraoral use. Duplicate, un-used samples were obtained from the manufacturers for direct comparison. The aligners were then sectioned into sizes that were compatible with the instrumentation being used to analyze them. Differential Scanning Calorimetry (DSC) was used to individually analyze the thermal properties of each sample. The resulting thermograms were then compared to investigate potential differences between brands and conditions. Of particular interest was the temperature at which each polymer went through the glass transition phase. Enthalpy relaxation, recrystallization temperature, and melting point were also analyzed. Results: There was no statistical difference in glass transition temperature between as-received and after use Invisalign, ClearCorrect, or Simpli5 aligners (p\u3e0.05). In addition, there was no significant difference in recrystallization peak and recrystallization enthalpy between as-received and after use Simpli5 aligners (p\u3e0.05). There was a significant decrease in melting peak and melting enthalpy between as-received and after use Simpli5 aligners (p\u3c0.05). A lack of recrystallization and melting peaks indicates that Invisalign and ClearCorrect are a thermoset material while the presence of these peaks indicates that Simpli5 is thermoplastic. All materials possessed a glass transition temperature above the maximum temperature that is found intraorally. Conclusions: Glass transition temperature did not significantly change after clinical use in the tested orthodontic aligners, indicating the stability of this property throughout normal treatment. All three types have a glass transition temperature above the maximum temperature that is found intraorally, which has been shown to be a benefit to an aligner’s mechanical properties. Melting peak and melting enthalpy showed a small decrease after use in Simpli5, indicating some structural aging intraorally

The angular spectrum of the scattering coefficient map reveals subsurface colorectal cancer

Abstract Colorectal cancer diagnosis currently relies on histological detection of endoluminal neoplasia in biopsy specimens. However, clinical visual endoscopy provides no quantitative subsurface cancer information. In this ex vivo study of nine fresh human colon specimens, we report the first use of quantified subsurface scattering coefficient maps acquired by swept-source optical coherence tomography to reveal subsurface abnormities. We generate subsurface scattering coefficient maps with a novel wavelet-based-curve-fitting method that provides significantly improved accuracy. The angular spectra of scattering coefficient maps of normal tissues exhibit a spatial feature distinct from those of abnormal tissues. An angular spectrum index to quantify the differences between the normal and abnormal tissues is derived, and its strength in revealing subsurface cancer in ex vivo samples is statistically analyzed. The study demonstrates that the angular spectrum of the scattering coefficient map can effectively reveal subsurface colorectal cancer and potentially provide a fast and more accurate diagnosis

Rates of lobar atrophy in asymptomatic MAPT mutation carriers.

IntroductionThe aim of this study was to investigate the rates of lobar atrophy in the asymptomatic microtubule-associated protein tau (MAPT) mutation carriers.MethodsMAPT mutation carriers (n = 14; 10 asymptomatic, 4 converters from asymptomatic to symptomatic) and noncarriers (n = 13) underwent structural magnetic resonance imaging and were followed annually with a median of 9.2 years. Longitudinal changes in lobar atrophy were analyzed using the tensor-based morphometry with symmetric normalization algorithm.ResultsThe rate of temporal lobe atrophy in asymptomatic MAPT mutation carriers was faster than that in noncarriers. Although the greatest rate of atrophy was observed in the temporal lobe in converters, they also had increased atrophy rates in the frontal and parietal lobes compared to noncarriers.DiscussionAccelerated decline in temporal lobe volume occurs in asymptomatic MAPT mutation carriers followed by the frontal and parietal lobe in those who have become symptomatic. The findings have implications for monitoring the progression of neurodegeneration during clinical trials in asymptomatic MAPT mutation carriers