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Home arrow Computer Science arrow Computational Diffusion MRI: MICCAI Workshop, Athens, Greece, October 2016


Results and Discussion

Statistical Evaluation of Left-Right Neurite Density Asymmetries

First of all, we checked the gaussianity of the fintra distributions using the Shapiro- Wilcoxon test. Then, for all the cortical regions taken from the Destrieux’s atlas [8], the signed differences of mean fintra between the left area and its associated right one were computed for all the subjects. A t-test was then applied on this list of left-right differences and finally, a False Discovery Rate (FDR) was computed to get rid of the false positives. We only represented on Fig. 4 brain areas depicting a significant

Left-right difference of fi in cortical regions

Fig. 4 Left-right difference of fintra in cortical regions

difference between left and right hemispheres and the color of the area corresponds to the difference using a rainbow colormap (the higher difference is shown in red).

Among the cortical regions where fintra(LH) > fintra(RH), we recognize the frontopolar cortex, the secondary motor area, the somatosensory primary cortex (central sulcus and postcentral gyrus but surprisingly not the left precentral gyrus), the auditory cortex and some areas involved in the language network (Broca’s area, Wernicke’s area, the inferior parietal lobule). As the language has been admitted to be left-lateralized in 80% of the right-handed population and about 75% of the left-handed population (cf. pioneer studies of language hemispheric lateralization using the Wada test [9] but also more recent corroboration of those numbers [10]), our findings seem to back up this cortical asymmetry. Furthermore, the link between handedness and language dominance for the right-handed volunteers is in adequation with the literature’s statements from [11].

On the other hand, by looking at the regions where fintra (RH) > fintra (LH), we can notice that a portion of the visual primary cortex is highlighted which seem to indicate a right lateralization in neurite density of this cortical region. A recent article [12] has studied the cerebral response to a simple visual stimulation and they suggest a right-hemispheric dominance of the concerned areas also in adequation with what we have found in our study; to be verified with the functional underlying activity in the next part.

To link the microstructure with the underlying functional activity, we guided our studies based on the Penfleld homonculus [13] using a motor hand, a reading and a visual contrasts.

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