FDG-PET mapping the brain substrates of visuo-constructive processing in Alzheimeŕs disease

Department of Nuclear Medicine, Ludwig-Maximilian University, Munich, Germany.
Journal of Psychiatric Research (Impact Factor: 3.96). 10/2009; 44(7):462-9. DOI: 10.1016/j.jpsychires.2009.09.012
Source: PubMed

ABSTRACT The anatomical basis of visuo-constructive impairment in AD is widely unexplored. FDG-PET can be used to determine functional neuronal networks underlying specific cognitive performance in the human brain. In the present study, we determined the pattern of cortical metabolism that was associated with visuo-constructive performance in AD. We employed two widely used visuo-constructive tests that differ in their demand on visual perception and processing capacity. Resting state FDG-PET scans were obtained in 29 probable AD patients, and cognitive tests were administered. We made a voxel-based regression analysis of FDG uptake to scores in visual test performance, using the SPM5 software. Performance in the CERAD Drawing test correlated with FDG uptake in the bilateral inferior temporal gyri, bilateral precuneus, right cuneus, right supramarginal gyrus and right middle temporal gyrus covering areas of dorsal and ventral visual streams. In contrast, performance in the more complex RBANS Figure Copy test correlated with FDG uptake in the bilateral fusiform gyri, right inferior temporal gyrus, left anterior cingulate gyrus, left parahippocampal gyrus, right middle temporal gyrus and right insula, encompassing the ventral visual stream and areas of higher-level visual processing. The study revealed neuronal networks underlying impaired visual test performance in AD. The extent of involvement of visual and higher order association cortex increased with greater test complexity. From a clinical point of view, both of these widely used visual tests evaluate the integrity of complementary cortical networks and may contribute complementary information on the integrity of visual processing in AD.

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Available from: Stefan Förster, Sep 29, 2015
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    • "The dorsal stream, including the precuneus (BA7) and the middle temporal gyrus (BA21), is also known as the " where/how pathway " , and it is implicated in spatial localization of objects and shape [54]. The atrophy we detected in all these cortical areas of ADca patients is likely to be crucial for their characteristic symptoms, as also suggested by a previous FDG-PET study [55]. "
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    ABSTRACT: Constructional apraxia (CA) is often, but not always, observed in patients with Alzheimer's disease (AD). CA is usually explained by impairment of either basic perceptual and motor abilities, or of executive functions. This study aims to evaluate the structural correlates of CA in AD. Forty-eight patients with AD and 20 healthy age-matched controls underwent a thorough neuropsychological investigation and an MRI scan to collect high-resolution T1-weighted data. Patients were classified as having (ADca) or not having (ADnonca) CA based on performance on the Freehand copying of drawings task. T1-weighted volumes were processed according the voxel-based morphometry protocol, to assess the presence of significant differences in local grey matter volume in patients compared to controls and in ADca compared to ADnonca. Post-hoc, the mean grey matter volume of clusters that resulted significantly different between groups was regressed against the neuropsychological scores in which the two patient groups performed differently. A pre-senile disease onset was significantly more frequent in patients with CA compared to ADnonca. ADca patients also showed worse performances than patients with ADnonca at some tests requiring the processing of visuo-spatial data and testing working memory. They also showed widespread reductions in grey matter volume, mainly located in areas known to be implicated in object recognition and localization, and in maintenance and re-orienting of spatial attention. These findings suggest that the occurrence of CA in AD is often associated with a peculiar clinical onset (i.e., pre-senile), neuropsychological profile, and distribution of grey matter atrophy.
    Journal of Alzheimer's disease: JAD 08/2013; 38(2). DOI:10.3233/JAD-130656 · 4.15 Impact Factor
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    • "The RBANS has also been reported to be predictive of functional capacity (i.e., driving) in patients with MCI (Badenes Guia, Casas Hernanz, Cejudo Bolivar, & Aguilar Barbera, 2008). The RBANS correlates with all six domains of the Clinical Dementia Rating Scale in patients with MCI and AD (Hobson, Hall, Humphreys-Clark, Schrimsher, & O'Bryant, 2010), and the RBANS has been shown to correlate with AD biomarkers, including functional neuroimaging data in patients with AD (Forster et al., 2010; Wilson et al., 2009). Finally, the RBANS has been shown to be sensitive to detecting cognitive enhancement in computer training designed to boost memory functioning in non-demented older adults (Mahncke et al., 2006) and in a small clinical trial in MCI (Kotani et al., 2006). "
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    ABSTRACT: Current diagnostic criteria for mild cognitive impairment (MCI) due to Alzheimer's disease (AD) require standardized tests that are capable of measuring a range of neurocognitive abilities in healthy elderly individuals and sensitive to detect change over time. There currently is no clearly-established "gold standard" for this purpose. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) is a widely used neuropsychological test battery for the clinical diagnosis/tracking of dementia also recently incorporated into clinical trials of new investigational medications for AD treatment. The RBANS has a number of design features that suggest possible utility in diagnosis/tracking of MCI. Eighty-one patients with MCI completed the RBANS and their scores were compared with 81 demographically matched healthy controls. RBANS Total Scale scores in both groups were normally distributed, demonstrating no floor/ceiling effects. The MCI group was most impaired on the Delayed Memory Index (DMI). Receiver operating characteristic analyses reflected good discrimination, with an area under the curve of 0.88 for the Total Scale score and 0.90 for the DMI score. The profile of performance for the MCI group was similar to that previously reported for mild AD patients. The RBANS may be a suitable neurocognitive battery for the detection and tracking of MCI presumed to be due to AD.
    Archives of Clinical Neuropsychology 07/2013; 28(8). DOI:10.1093/arclin/act057 · 1.99 Impact Factor
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    • "The right hemisphere is known to be mainly involved in visuospatial ability and attention, musical, and emotional functions (Joseph, 1988), whereas the left hemisphere is deemed to be predominantly associated with language and its related semantic knowledge processing (Geschwind and Galaburda, 1985; Foxe et al., 2003; Caplan, 2006; Bartolomeo et al., 2012). Especially, the right inferior temporal gyrus (BA 20) has been implicated in cortical processing of complex visual objects including face or clock (Forster et al., 2010), and the right inferior parietal regions including the supramarginal (BA 40) and angular gyri (BA 39) are vital for good visuoconstructive performance (Villa et al., 1986). Patients with lesions in the right BA 39/40 usually very poorly copy and depict the size, shape, proportions, and relationships of visual percepts (Caplan, 2006). "
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    ABSTRACT: The executive clock drawing task (CLOX) is one of the widely used clock drawing tests (CDTs) and composed of CLOX1, an unprompted CDT, and CLOX2, a simple copying CDT. Although it is conceptually believed that CLOX1 is sensitive to both executive function and constructional ability while CLOX2 reflects only constructional ability, there are still lack of studies on the functional neuroanatomical substrates of CLOX1 and 2 performances. This study aimed to identify the functional brain correlates of CLOX1 and 2 performances in patients with Alzheimer's disease (AD). CLOX was administered to 139 AD patients and 50 normal controls, and regional cerebral glucose metabolism (rCMglc) was measured by (18)F-fluoro-2-deoxy-glucose positron emission tomography. Correlations between CLOX scores and rCMglc were examined on a voxel-by-voxel basis in AD patients. For overall AD group, significant positive correlations between CLOX1 and rCMglc were found in the bilateral temporo-parietal and left middle frontal regions, while CLOX2 was correlated with rCMglc of the bilateral temporo-parietal regions. Additional subgroup analysis showed that CLOX1 was associated with the left temporal metabolism in less severe AD, and with the right temporo-pariteal metabolism in more severe AD. In contrast, CLOX2 was correlated with rCMglc of the diffuse right fronto-temporo-parietal regions in more severe AD, but not with any rCMglc in less severe AD. This is the first neuroimaging study on the functional neuroanatomical correlates of CLOX performances in AD. Given the relationships between specific cognitive performances and regional brain functions, the findings probably support the notion that CLOX1 demands not merely visuospatial functions but also executive control, while CLOX2 depends mainly on visuospatial ability. Our results also indicate that each CLOX performance depends on very different functional brain regions according to AD clinical stages.
    Neuroscience 05/2013; 246(4). DOI:10.1016/j.neuroscience.2013.05.008 · 3.36 Impact Factor
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