Computational protocol: Auditory spatial processing in Alzheimer’s disease

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Protocol publication

[…] Preprocessing of patient brain magnetic resonance images for voxel-based morphometry was performed using New Segment and the DARTEL toolbox of SPM8 (www.fil.ion.ucl.ac.uk/spm) running under Matlab2012a® (; ). Normalization, segmentation and modulation of grey and white matter images were performed using default parameter settings, with a smoothing Gaussian full-width at half-maximum of 6 mm. To adjust for individual differences in global grey matter volume during subsequent analysis, total intracranial volume was calculated for each participant by summing grey matter, white matter and CSF volumes following segmentation of all three tissue classes. A study-specific mean brain image template was created by warping all bias-corrected native space whole-brain images to the final DARTEL template and calculating the average of the warped brain images.Generalized linear models were used to examine regional grey matter volume correlations with performance on auditory experimental tasks for which the combined patient cohort exhibited deficits compared to the healthy control group in the behavioural analysis. For each task, voxel intensity (grey matter volume) was modelled as a function of experimental test score across the combined patient cohort, within each syndromic group and comparing syndromic groups, including syndromic group, age, total intracranial volume, gender and reverse digit span total score as covariates of no interest. In addition, grey matter correlates of performance on the visual spatial discrimination tasks within the typical Alzheimer’s disease group was assessed in a separate model. To help protect against voxel drop-out due to marked local regional atrophy, we applied a customized explicit brain mask based on a specified ‘consensus’ voxel threshold intensity criterion () whereby a voxel was included in the analysis if grey matter intensity at that voxel was > 0.1 in > 70% of participants (rather than in all participants, as with the default SPM8 mask).Statistical parametric maps (SPMs) of regional grey matter volume correlating with score on each auditory experimental test were examined at threshold P < 0.05 after family-wise error (FWE) correction for multiple comparisons over the whole brain and after small volume correction using anatomical regions based on our previous anatomical hypotheses. Anatomical small volumes were derived from the Oxford-Harvard brain maps () in FSLview () and edited using MRIcron (www.mccausandcentre.sc.edu/micro/micron) for the study-customized template brain image. These small volumes included key areas previously implicated in auditory scene analysis and spatial processing (; ; ; ; ; ): posterior superior temporal lobe and inferior parietal lobe (supramarginal and angular gyri) and retrosplenial cortex (posterior cingulate and precuneus) in each cerebral hemisphere. […]

Pipeline specifications

Software tools SPM, MRIcron
Application Magnetic resonance imaging
Organisms Homo sapiens
Diseases Alzheimer Disease, Brain Diseases