Computational protocol: Too Little, Too Late: Reduced Visual Span and Speed Characterize Pure Alexia

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Protocol publication

[…] A single T1 weighted magnetic resonance imaging (MRI) brain scan was obtained for each subject. 1.5-T scanners were used at 2 different locations, both protocols collected data in 1-mm3 isotropic voxels. In order to produce a lesion overlap map, the images were spatially normalized using SPM5 software (http://fil.ion.ucl.ac.uk/spm). The unified segmentation algorithm was chosen as this has the best performance for lesioned brains (). After spatial normalization, the resultant images were imported into another software package, MRIcro (http://www.psychology.nottingham.ac.uk/staff/cr1/mricro.html), for lesion identification. Lesions were outlined by eye by one of us (APL), transformed into binary images and then overlaid on the single-subject canonical brain image available in SPM5. The resultant image was displayed at the mean coordinates for the VWFA as estimated by a meta-analysis of 27 functional imaging data sets (); see . The only lesioned voxels common to all 4 patients are at the junction between the mid and posterior portion of the left fusiform gyrus, corresponding to the putative VWFA.NT's images have been published (see ). He suffered a primary intracerebral hemorrhage that damaged the inferior and lateral part of the occipital lobe, with some extension into the posterior part of the temporal lobe. The lesion centers on the inferior and fourth occipital gyri (O3, O4), with the lingual gyrus (O5) and striate cortex (V1) spared. More anteriorly, the medial part of the posterior portion of the fusiform gyrus is just affected. The voxel at the center of the lesion overlap in the 4 pure alexic patients (−44 −58 −15, see ) is spared in NT; indeed, working posteriorly from this coordinate, the lesion does not appear until y = −78 (2 cm posterior to this point). […]

Pipeline specifications

Software tools SPM, MRIcro
Application Magnetic resonance imaging
Organisms Homo sapiens