Brain activation patterns during imagined locomotion in blind subjects

Objective: To investigate differential brain activation patterns during imagined locomotion in congenitally blind versus sighted subjects.

Methods: Seven congenitally blind subjects imagined to walk and run during a functional magnetic resonance imaging (BOLD-fMRI) study. Imagined lying served as rest condition. Seven age- and gender-matched healthy sighted subjects served as a control group. Thirty-two transversal slices covered the whole supratentorial brain and most parts of the cerebellum. Data analysis was performed using SPM2. Group analyses and intergroup comparisons were calculated, and a significance threshold of p<0.001 was applied.

Results: Blind subjects showed bilateral activations in the posterior insula and adjacent temporal areas, which correspond best to the human homologue of the parieto-insular vestibular cortex (PIVC), while sighted subjects deactivated these areas. Sighted subjects showed higher blood oxygen level dependent (BOLD) activity levels in the right parahippocampal gyrus than blind subjects. While sighted subjects showed bilateral BOLD signal increases in the parahippocampal gyri, blind subjects, as a trend, displayed parahippocampal BOLD signal decreases. Further, blind subjects had stronger activations of supratentorial cortical areas (M1, SMA) than sighted subjects.

Conclusion: Using fMRI, we found evidence for different locomotion strategies in blind subjects without any visual memories versus sighted subjects. We propose that sighted subjects activate parahippocampal areas during navigation and deactivate vestibular cortex areas during locomotion to prevent adverse interactions with the optimized spinal locomotion pattern. Blind subjects use input of vestibular cortex areas for navigation.