The sense of verticality results from a complex multisensory integration suggesting the existence of internal models of verticality perception. Recent data from our team suggest that the parietal operculum, the posterior insula and the posterior-lateral thalamus, in the right hemisphere, constitute the core polymodal regions that construct and update the internal models of verticality.

The aim of this study was double. First, to analyse functional connectivity, in a group of healthy participants, of the three core regions in a larger verticality perception network, established on literature data. Second, to analyse functional connectivity of these three regions in a group of stroke patients presenting an altered perception of verticality.

Functional connectivity was studied using ROI-to-ROI method in Connectivity toolbox with resting state functional Magnetic Resonance Imaging (fMRI). The regions of interest were selected from Anatomy toolbox, with source regions OP1, OP2, Ig1, Ig2, parietal and somatosensory thalamus. The first study concerned 74 healthy participants and the second study concerned 5 stroke patients with altered verticality perception in visual modality.

In the healthy participants group, the three regions (represented by OP1, OP2, Ig1, Ig2, ThP and ThS) constitute a highly connected network in both hemispheres. In stroke patients group, this network was globally preserved in the healthy hemisphere, but disrupted in the brain-damaged hemisphere. Moreover, we observed a correlation between the loss of inter-hemispheric connectivity within this network and the altered perception of verticality in the visual modality.

The parietal operculum, the posterior insula and the posterior-lateral thalamus form a network that could correspond to the ‘sense of upright’ network.