Robinson et al., "A multimodal parcellation
of human cerebral cortex," Nature, vol.
Provided that modularity is most likely the derived state in the phylogeny of animals and is perhaps the result of parcellation
rather than integration, the question arises of how parcellation
has been caused by natural selection.
The final parcellation
contained 780 nodes (Figure 1).
First, different parcellation
schemes and graph building methods were used including independent components based graphs, brain regions based graphs and voxel based graphs.
As further exploratory analysis of the topographic effects, we extracted average measures of PSD and PLV from regions of interest (ROIs) derived from a parcellation
of the cortical surface implemented in Brainstorm  and we compared the real versus sham stimulations by means of t-tests.
Segmentation of the brain in white matter, grey matter, and Cerebrospinal Fluid (CSF) with T1 weighted image needs to be performed, and on this basis the brain cortical is divided into 83 brain regions by using Automated Anatomical Labeling (AAL) template in Cortical Parcellation
with FreeSurfer , which will serve later on as 83 nodes of the brain structural network.
However, these investigations, based on a priori selection of regions of interest (ROIs) capturing the activity of a given region/network , or based on an arbitrary anatomo-functional parcellation
of the brain , might lead to a partial view of the possible insomnia-related alteration of brain activity, induced by sampling the activity of a limited subset of cortical and subcortical regions fitting with a given theory or pathophysiological model.
Some of the proposed downsampling solutions are based on anatomical parcellation
either exploiting information provided by a Brain Atlas or based on a clustering procedure in the anatomical space [14,15].
Nakamura et al., "A hierarchical algorithm for MR brain image parcellation
," IEEE Transactions on Medical Imaging, vol.
Tzouriomazoyer et al., "Automated anatomical labeling of activations in SPM using a macroscopic anatomical parcellation
of the MNI MRI single-subject brain," Neuroimage, vol.
This cortical parcellation
was done for each patient using a multiatlas label propagation approach.
Specifically, the Harvard-Oxford cortical atlas (http:// neuro.imm.dtu.dk/wiki/Harvard-Oxford_Atlas) was used, thus resulting in a brain parcellation
of 96 regions, 48 per hemisphere.