Network coherence in autism spectrum disorder : a multimodal neuroimaging study of functional connectivity and spectroscopy MRI

The underlying neuropathology and effects on neuronal activity in individuals with ASD are still being elucidated; as well as their impact on intervention and treatment outcomes. Frontal, temporal, parietal and cerebellar pathways exhibit disrupted structural and functional connectivity in individuals with ASD and we sought to investigate the potential clinical utility of altered network coherence. Beta-adrenergic antagonism improved information processing in a subset of individuals with ASD and improved performance was related to pharmacologicallymediated alterations in functional connectivity in the fronto-parietal control network. These findings support the potential utility of beta-adrenergic antagonists for some patients with ASD and the clinical significance of alterations in network coherence. There are also additional considerations for functional connectivity investigations in ASD. The cerebellum is interconnected via feedback loops to the neocortex and thus has some modulatory influences on cortical and subcortical neuronal circuits. The cerebellum is consistently implicated in the neuropathology of ASD but has been largely ignored in investigations of functional network coherence. Functional connectivity between the cerebellum and neocortex was anticorrelated in a subset of individuals with ASD. These individuals exhibited reduced glutamate levels in the cerebellum and diminished interpretive linguistic abilities, suggesting a potential mechanism underlying altered cerebrocerebellar connectivity in some individuals with ASD as well a cognitive outcome of alterations in cerebrocerebellar network coherence

Assessment of associations of known AD risk factors and the medial temporal and orbitofrontal lobes a volumetric MRI study

Title from first page of PDF file (viewed November 19, 2010)Includes bibliographical references (p. 49-59)Alzheimers disease (AD) has been recognized as the most common type of dementia in the United States affecting more than 4.5 million people, as measured by the 2000 census, and the prevalence is expected to increase exponentially over the next 50 years. AD is a progressive form of dementia that is marked by cognitive decline and cortical atrophy caused by neuritic plaques and neurofibrillary tangles. The neuropathology of AD can precede clinical symptoms by years, and thus widespread anatomical alterations can be present well before behavioral symptoms are noted. Therefore, pre-clinical diagnosis of AD has become an increasingly important line of research with aims to treat the disease before detrimental functional effects have occurred. The present study investigated the associations between known AD risk factors including age, education, and genetic status as well as the correlate of diminished olfactoryprocessing. Each of 39 older participants (aged 62 to 88) were tested on several risk factors including age, education levels, and APOE E4 status as well several indices of cognitive (Dementia Rating Scale, California Verbal Learning Test, and Boston Naming Test) and olfactory (Odor Threshold, Odor Identification, California Odor Learning Test, and Alcohol Sniff Test) processing. Anatomical MRI scans were also taken which were utilized in a volumetric MRI study. Areas that were segmented include the olfactory bulbs, entorhinal cortex, amygdala, hippocampus, orbitofrontal cortex, and a control region, the primary visual cortex. It was found that: (1) group analysis based on APOE E4 status revealed lower volumes on average for APOE E4+ subjects in the entorhinal cortex, hippocampus, amydala, and orbitofrontal cortex compared to APOE E4- subjects, (2) olfactory measures were significant predictors of the underlying volumes of the medial temporal lobe structures, (3) olfactory measures provide significant associations with MTL volumes beyond cognitive measures, and (4) predictive models of the hippocampus and entorhinal cortex change based on APOE E4 status

Morphological differences in the lateral geniculate nucleus associated with dyslexia

Developmental dyslexia is a common learning disability characterized by normal intelligence but difficulty in skills associated with reading, writing and spelling. One of the most prominent, albeit controversial, theories of dyslexia is the magnocellular theory, which suggests that malfunction of the magnocellular system in the brain is responsible for the behavioral deficits. We sought to test the basis of this theory by directly measuring the lateral geniculate nucleus (LGN), the only location in the brain where the magnocellular and parvocellular streams are spatially disjoint. Using high-resolution proton-density weighted MRI scans, we precisely measured the anatomical boundaries of the LGN in 13 subjects with dyslexia (five female) and 13 controls (three female), all 22–26 years old. The left LGN was significantly smaller in volume in subjects with dyslexia and also differed in shape; no differences were observed in the right LGN. The functional significance of this asymmetry is unknown, but these results are consistent with the magnocellular theory and support theories of dyslexia that involve differences in the early visual system