NMF in Screening Some Spirometric Data, an Insight into 12-Dimensional Data Space

Part 3: Data Analysis and Information RetrievalInternational audienceWe present the usage of the Non-negative Matrix Factorization (NMF), an unsupervised machine learning method, which learns normal and abnormal state of patient’s ventilatory systems. This is done using samples of patients having defects of obturative and restrictive kind and a control group.We show that the NMF method can identify patients being in the normal state and screen them off from the remaining patients; however the kind of the ventilatory disorder for the remaining patients is not recognized. This is confronted with clustering provided by the k-means method and visualization of the 12-dimensional data using heatmaps and Kohonen’s self-organizing maps.The data set can be reconstructed with a 0.9746 accuracy (fraction of explained variance) from 6 base vectors provided by the NMF and using appropriate encoders provided also by the NMF; while 3 factors yield an 0.8573 fraction of explained variance

Lateralization of the visual word form area in patients with alexia after stroke

Background Knowledge of the process by which visual information is integrated into the brain reading system promotes a better understanding of writing and reading models. Objective This study aimed to use functional Magnetic Resonance Imaging (fMRI) to explore whether the Blood-oxygen-level dependent (BOLD) contrast imaging patterns, of putative cortical region of the Visual Word Form Area (VWFA), are distinct in aphasia patients with moder- ate and severe alexia. Methods Twelve chronic stroke patients (5 patients with severe alexia and 7 pa- tients with moderate alexia) were included. A word categorization task was used to examine responses in the VWFA and its right homolog re- gion. Patients performed a semantic decision task in which words were contrasted with non-verbal fonts to assess the lateralization of reading ability in the ventral occipitotemporal region. Results A fixed effects (FFX) general linear model (GLM) multi-study from the contrast of patients with moderate alexia and those with severe alexia (FDR, p = 0.05, corrected for multiples comparisons using a Threshold Estimator plugin (1000 Monte Carlo simulations), was per- formed. Activation of the left VWFA was robust in patients with mod- erate alexia. Aphasia patients with severe reading deficits also activated the right homolog VWFA. Conclusions This bilateral activation pattern only in patients with severe alexia could be interpreted as a result of reduced recruitment of the left VWFA for reading tasks due to the severe reading deficit. This study provides some new insights about reading pathways and possible neuroplasti- city mechanisms in aphasia patients with alexia. Additional reports could explore the predictive value of right VWFA activation for reading recovery and aid language therapy in patients with aphasia.N/