Neural correlates of disturbed perception of verticality.

Objective: Perception of verticality can be perturbed after cortical stroke. However, a relationship between lesion location and pathologic perception of verticality is still a matter of debate since previous studies revealed contradictory results. Thus, the aim of the current study was to test whether specific cortical lesions were associated with tilts of subjective visual vertical (SVV) and to determine the critical brain areas that cause such tilts in the case of a lesion.

Methods: SVV was systematically studied in 54 patients (22 patients with left-sided and 32 patients with right-sided lesions) with acute unilateral strokes, analyzed by modern voxel-wise lesion-behavior mapping techniques.

Results: The data give evidence for an association between tilt of SVV and the insular cortex (IC) and inferior frontal gyrus (IFG) in both hemispheres. Whereas the IC seems to be the prominent structure in the left hemisphere, the IFG is most affected in the right hemisphere. Furthermore, other cortical regions such as the superior temporal gyrus (STG) and the rolandic operculum as well as-subcortically-the inferior occipitofrontal fascicle and the superior longitudinal fascicle seem to be involved in the vestibulo-cortical network for the perception of verticality in the roll plane.

Conclusion: Damage to these regions might lead to an imbalance within the vestibular network of one hemisphere due to a deficit in multimodal signal processing.