Expanded Spatiotemporal Concept of Cortical Visual-Vestibular Interaction in Humans: A fMRI Study on Visually Induced...

This high-resolution fast fMRI study explores visual-vestibular network interactions in expanded spatial and temporal detail. Under natural conditions coherent visual motion always occurs during self-motion. Technology applying coherent visual motion on stationary subjects creates visual-vestibular mismatch and allows investigation of system interplay in the MRI. In humans, the process minimizing the intersensory conflict was previously conceptualized as a categorical reciprocal upregulation of one (e.g., visual) and downregulation of the other system (e.g., vestibular), or vice versa.

Healthy participants (n = 22) were tested with a two-phase paradigm using different coherent visual dot motion stimulation conditions (stimulation phase) and subsequent variable duration illusory self-motion perception while the visual pattern was stationary, called motion aftereffect (MAE, post-stimulation phase). A matched random dot stimulus, not inducing self-motion perception, served as the control. Signal modulations related to subjective illusory self-motion (MAE duration) were identified in a multivariate temporal model-free way.

Visual areas showed uniform positive signal curves with motion stimulation unrelated to self-motion perception (MAE duration), except for V5/MT. In contrast, vestibular areas exhibited fourfold signal patterns along the dimensions of transient versus sustained decreases and in relation to the stimulus phases and presence of correlation with MAE duration. Notably, beside V5/MT, further areas with intermediate signaling were identified.

Altogether, in contrast to the visual system, the vestibular network areas exhibited greatly differentiated processing instead of a categorical uniform system "on-off" mode. These novel findings expand our comprehension of the continuous interaction between the visual and vestibular systems, especially with respect to the various dynamical activity changes in vestibular areas, potentially indicating subspecialization of regions that might be essential even for humans moving in the real world.